Acf Subsistence Fish Farming

ACF - INTERNATIONAL NET WORK

The subsistence fishfarming in Africa: Technical Manual

Yves FERMON

In collaboration with:

Aımara

Cover photos: ÖÖ Top right: Tilapia zillii - © Anton Lamboj ÖÖ Top left: Pond built by ACF in DRC, 2008 - © François Charrier ÖÖ Bottom: Beneficiaries in front of the pond they have done, Liberia, ASUR, 2006 - © Yves Fermon

ii

Subsistence fishfarming in Africa

OBJECTIVES OF THE MANUAL ÖÖThe objective of the handbook is to bring to the essential elements for the installation of production of animal proteins “fish” to lower costs in relation to the existing natural resources and with a minimum of external contributions. This in a context of subsistence. ÖÖIn this case, it is a question above all of proposing an information system strategic plan of a system making it possible to produce consumable fish in the shortest possible time, and with lower costs to mitigate the lack of animal proteins. This does not prevent the installation of structures having a certain durability. The unit must be adapted to the environmental context. In this work, it is a question of providing a guide: ¾¾ To program managers and their technical teams, ¾¾ To managers at headquarters to monitor the success of programs. This manual covers: ÖÖ The various stages of setting up a «fishfarming» program, As of the arrival on the ground, it is a question of evaluating the renewable resources present, the needs for the populations and the already existing supply in fish. Then, a whole process is connected involving the technical sides of the installation of fish ponds, follow-ups of the biological aspects of the ponds. Finally, it is a question of managing and of carrying out a follow-up of the ponds and production of fish. ÖÖ The constraints that must be taken into account by the field actors. Various constraints will influence the choice for the development of fish production or not and what kind of techniques for a good fit with human needs and the environment. They are environmental, in conjunction with the available resources, geomorphology, climate and hydrology of the area of intervention. But they are also a social and cultural development, with the beliefs and taboos, land issues and laws. The fact that, according the region of intervention, the ethnic and social groups and countries, modes of intervention will be different.

WHY ANOTHER HANDBOOK?

Several organizations have published manuals for the establishment of fish farms in Africa. The first books calling systems in place at the time of the colonial system, but as a fish production for food self-sufficiency. However, after many trials, the majority of them has proved unsustainable in the longer term, for various reasons. The studies undertaken by different agencies of national or international research as the WorldFish Center (formerly ICLARM), CIRAD, IRD (ex ORSTOM), Universities of Louvain and Liège ... have provided evidence concerning the failures and have provided solutions and contributions to knowledge in both technical, social or biological species used. However, looking at all the works, one can put forward four points: 99 Most handbooks are intended for production systems of fish for sale, involving: ¾¾ A temporal investment which can become important and which leads to a professionalisation. This requires a technology with the appropriate training of technicians on aspects of reproduction, nutrition or health of fish, either for the establishment of systems to produce food to feed all the fish... Application requires external inputs whose supply may become a barrier for small producers. ¾¾ Financial investment for, sometimes, land, establishment of ponds, the use of workers, qualified technicians…

Subsistence fishfarming in Africa

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99 The handbooks do not take account of the local biodiversity. Indeed, many introductions and movements of species were made with the intention to set up farms and caused significant disruption to the balance of ecological systems. 99 Whereas these documents present solutions which appear universal, the great variation of the geomorphology, hydrology and the climate in Africa will make that there exist conditions very different according to the zones from interventions. 99 Few works also reflect the socio-ethnological aspects. Educational levels, beliefs and cultures of different peoples and the appropriation of this type of project by the people is often put forward, despite real progress in recent years. 99 Most of these books are made for aspects related to development and therefore with a potentiality of longer temporal installation.

LIMITS OF THIS HANDBOOK

This handbook is primarily a guide to give to the actors the stages and procedures to be followed. However, it will be necessary to adapt these stages and procedures according to the context in which the actions will be undertaken: 99 From a social, cultural and political point of view ¾¾ Culture and belief Food taboos exist, to varying degrees in all cultures. It is obvious that food, the basic element for the subsistence of man, is a field where the distinction between allowed and forbidden, the pure and impure, is fundamental for health reasons, moral or symbolic systems. ¾¾ Local law Each country is governed by laws concerning wildlife protection and movement of species from one region to another. These laws can be enacted at the regional level and at all administrative levels, to the village itself. They may be linked to land issues. 99 From an environmental point of view: ¾¾ Biodiversity and available resources The fauna of African fish includes over 3200 described species belonging to 94 families, but all are not exploitable. The distribution is not uniform across the continent and some species are known only of well delimited zones. For example, the African Great Lakes have a fauna whose majority of the species are endemic there. This means to act with a good knowledge of the fauna compared to the potentially exploitable species and the ecological risks of damages that could be related to the establishment of a fishfarming. ¾¾ Geomorphology, climate and hydrology If wildlife is so diverse across the continent, it is the result of historical and geological events that led Africa over millions of years. This has caused major hydrological changes. On a smaller time scale, climate variations are crucial for the viability of a fish. The availability of water, with its different uses (drinking, domestic, agriculture ...) is a limiting factor and a source of conflict. The type of terrain and the nature of the soils of the region will lead to technical problems for the achievement of the pond it will be solved.

THE STEPS

The first handbook is intended for internal use to Action Against Hunger network, therefore, with restricted diffusion. If possible and requests, a handbook with corrections and revisions will be proposed later. Then, an external diffusion to ACF could be considered.

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Subsistence fishfarming in Africa

ACRONYMS

ACF/AAH: Action Contre la Faim / Action Against Hunger AIMARA: Association de spécialistes oeuvrant pour le développement et l’application des connaissances sur les poissons et les relations Homme-Nature APDRA-F: Association Pisciculture et Développement Rural ASUR:

Association d’Agronomie et Sciences Utiles à la Réhabilitation des populations vulnérables

CIRAD:

Centre de coopération Internationale en recherche Agronomique pour le Développement

CNRS:

Centre national de la recherche scientifique

FAO:

Food and Agriculture Organization of the United Nations

IRD:

Institut de Recherche pour le Développement

MNHN:

Muséum national d’Histoire naturelle

UNO:

United Nation Organisation

NGO:

Non Governemental Organisation

GIS:

Geographic Informatic System

BDC:

Biological Diversity Convention

IBI:

Integrity Biological Indice

DRC:

Democratic Republic of Congo (ex-Zaïre)

Subsistence fishfarming in Africa

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Aımara

Association of specialists working for the development and the application of knowledge on fish and Man-Nature relationships

The aquatic environments and the management of water represent one of the major stakes for the decades to come. The fish are a source of proteins of good quality for the human consumption, but also a source of income considerable for the developing as developed countries. However, demography, the urban development, the installation of the rivers, industrialization, the climate changes, deforestation… have irreversible consequences on the water courses and the biodiversity and thus on the men who live of these resources.

� Goals

Research 99 To acquire new ichthyologic knowledge - systematic, biology, ecology, ethology… - on the fresh water, brackish and marine species; 99 To highlight knowledge and practices relating to fishing and management of the biodiversity and their modes of transmission. Diffusion of knowledge 99 To disseminate the results to the local populations, the general public and the scientific community by publications, exhibitions, contacts with the media and Internet. Sustainable management of environment and resources 99 To sensitive by using the social, cultural, food, economic and patrimonial values of the species with the aim of the conservation, of the management and of the preservationof the biodiversity; 99 To collaborate with the local actors in the durable management of the aquatic resources.

� Scope of activities

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• •

Studies of the characteristics of environments and impacts; Studies of the biology, biogeography, ecology and behavior of species;

• • • •

Anthropological and socio-economic relations man - Nature studies; Ecosystem modeling, statistical analysis: Development of databases; Association AÏMARA Expertise and faunistic inventories. 50 avenue de La Dhuys 93170 Bagnolet - FRANCE [email protected]

Subsistence fishfarming in Africa

ACKNOWLEDGEMENTS

ÖÖ

ACF



Devrig VELLY - Senior Food Security advisor, AAH



Cédric BERNARD - Food Security advisor in DRC, AAH



François CHARRIER - Food Security advisor in DRC, AAH, Rereader

ÖÖ

Aimara



François MEUNIER - Emeritas Professor at MNHN, President of AIMARA, Rereader



Patrice PRUVOST - Secretary of AIMARA



Hélène PAGÉZY - Researcher, CNRS

ÖÖ

Other collaborators



Roland BILLARD - Emeritas Professor at MNHN, Rereader



Didier PAUGY - Research Director at IRD



Thierry OBERDORFF - Research Director at IRD



Jérome LAZARD - Research Director at IRD



Alain BARBET - Agronomist



Anton LAMBOJ - Researcher, University of Vienna, Austria.



Mickael NEGRINI - Fishfarming technician



Kirk WINNEMILLER - Researcher, University of Texas, USA



Étienne BEZAULT - Researcher, EAWAG, Switzerland



Fabien NANEIX - Teacher

Subsistence fishfarming in Africa

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CONTENTS Part I - INTRODUCTION AND THEORICAL ASPECTS

1

Chapter 01 - FISHFARMING: AIM AND ISSUES

3

I. WHY?

3

II. PRESSURE ON THE RESOURCES

6

II.1. Modifications of the habitat II.2. Water pollution II.3. Fisheries impact II.4. Introductions III. INTERNATIONAL ASPECTS

12

IV. OBJECTIVE OF FISHFARMING

13

Chapter 02 - TYPE OF FISHFARMING

15

I. VARIOUS TYPES OF FISHFARMING

15

II. SOME HISTORY…

17

III. A FISHFARMING OF SUBSISTENCE: GOAL AND PRINCIPLE

17

IV. POLYCULTURE VS MONOCULTURE

18

Chapter 03 - BIOGEOGRAPHY AND FISH SPECIES

21

I. GEOGRAPHY

21

II. THE SPECIES II.1. The Cichlidae II.2. The Siluriformes or catfishes II.3. The Cyprinidae II.4. Other families and species

21 22 23 23 24

SUMMARY - PART 01

25

Part II - PRACTICAL ASPECTS

27

Chapter 04 - THE INITIAL PRE-PROJECT ASSESSMENT

33

I. THE ECOSYSTEM

33

II. THE ASSESSMENT

36

III. PRINCIPLE

37

IV. BIOLOGICAL AND ECOLOGICAL ASSESSMENT

38

V. SOCIO-ETHNOLOGY V.1. Socio-economic and cultural characteristics

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6 8 9 9

Subsistence fishfarming in Africa

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V.2. The relations man-resources V.3. The relations man-man

40 41

Chapter 05 - VILLAGES AND SITES SELECTIONS

43

I. THE VILLAGES SELECTION

43

II. THE SITES SELECTION II.1. The water II.2. The soil II.3. The topography II.4. The other parameters

45 45 50 53 56

Chapter 06 - CHARACTERISTICS OF THE PONDS

59

I. DESCRIPTION

59

II. TYPES OF PONDS II.1. Barrage ponds II.2. Diversion ponds II.3. Comparison

59 62 62 62

III. CHARACTERISTICS III.1. General criteria III.2. Pond shape III.3. According the slope III.4. Layout of ponds III.5. Size and depth of the ponds III.6. Differences in levels

63 63 66 67 67 68 69

IV. SUMMARY

71

Chapter 07 - THE CONSTRUCTION OF POND

73

I. THE DESIGN PLAN

73

II. THE CLEANING OF THE SITE

75

III. WATER SUPPLY: WATER INTAKE AND CHANNEL

77

IV. DRAINAGE: CHANNEL OF DRAINING AND DRAINAGE

81

V. THE PICKETING OF THE POND

82

VI. THE CONSTRUCTION OF THE DIKES

83

VII. THE DEVELOPMENT OF THE PLATE (BOTTOM)

89

VIII. THE CONSTRUCTION OF THE POND INLET AND OUTLET VIII.1. Pond inlet structures VIII.2. Pond outlet structures VIII.3. Sedimentation tank

90 90 94 105

IX. ADDITIONAL INSTALLATIONS IX.1. The anti-erosive protection IX.2. The anti-erosive fight IX.3. Biological plastic

106 106 107 108

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x

IX.4. The fence IX.5. The filling of the pond and tests

108 109

X. NECESSARY RESOURCES X.1. Materials X.2. Human Resources and necessary time

109 109 110

XI. SUMMARY

112

Chapter 08 - BIOLOGICAL APPROACH

113

I. THE LIFE IN A POND I.1. Primary producers I.2. The invertebrates I.3. The vertebrates

113 115 116 118

II. THE FERTILIZATION II.1. The fertilizers or manure II.2. The compost

118 118 121

III. SUMMARY

126

Chapter 09 - THE HANDLING OF THE FISH

127

I. CATCH METHODS I.1. Seine nets I.2. Gill nets I.3. Cast nets I.4. Dip or hand nets I.5. Traps I.6. Handline and hooks

127 129 132 133 134 135 136

II. THE TRANSPORT OF LIVE FISH

136

III. THE PRODUCTION OF FINGERLINGS OF TILAPIA III.1. The recognition of the sex III.2. The nursery ponds III.3. Hapas and cages III.4. The other structures

139 139 139 142 145

IV. THE STOCKING OF THE PONDS

146

V. THE FOLLOW-UP OF FISH

149

VI. DRAINING AND HARVEST VI.1. Intermediate fishings VI.2. Complete draining

150 150 151

VII. SUMMARY

152

Chapter 10 - MAINTENANCE AND MANAGEMENT OF THE PONDS

153

I. THE MAINTENANCE OF THE PONDS I.1. The diseases of fish I.2. The feeding of the fish I.3. Daily activities of follow-up I.4. Maintenance work after draining

153 153 158 162 163

Subsistence fishfarming in Africa

I.5. Fight against predators I.6. Summary

164 164

II. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION

165

III. THE MANAGEMENT OF PONDS III.1. Fish Stocks and useful indices for monitoring III.2. The expected yields III.3. The management of harvests III.4. Several kinds of production costs III.5. Record keeping and accounting III.6. The formation

167 167 168 168 170 170 171

IV. PONDS AND HEALTH

171

GENERAL SUMMARY

173

REFERENCES

177

GLOSSARY

179

APPENDIX

187

Appendix 01 - EXAMPLES OF FILES

189

I. FILES FOR MONITORING THE PONDS

189

II. FILES FOR THE FOLLOW-UP OF THE FISH

191

Appendix 02 - TABLE OF DATA

193

Appendix 03 - SOME ELEMENTS OF THE BIOLOGY OF THE SPECIES

207

I. THE MORPHOLOGY AND THE SYSTEMATIC

207

II. THE BIOLOGY OF CICHLIDAE II.1. The taxonomy II.2. The feeding habits II.3. The reproduction and parental care

216 216 217 218

III. THE BIOLOGY OF SILURIFORMES OR CATFISH III.1. The Clariidae III.2. The Claroteidae and Auchenoglanididae III.3. The Schilbeidae III.4. The Mochokidae

226 226 231 233 233

IV. THE OTHER FAMILIES IV.1. The Cyprinidae IV.2. The Citharinidae IV.3. The Distichodontidae IV.4. The Channidae IV.5. The Latidae IV.6. The Arapaimidae

234 234 234 236 236 237 237

Appendix 04 - BIOGEOGRAPHIC DATA

239

Appendix 05 - FILE OF SPECIES

255 Subsistence fishfarming in Africa

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LIST OF FIGURES Part I - INTRODUCTION AND THEORICAL ASPECTS Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7.

1 3 5 5 6 14 19 22

Part II - PRACTICAL ASPECTS

27

Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Figure 19. Figure 20. Figure 21. Figure 22. Figure 23. Figure 24. Figure 25.

32 34 35 36 44 46 46 46 47 47 47 48 49 50 51 51 52

Figure 26. Figure 27. Figure 28. Figure 29. Figure 30. Figure 31. Figure 32. Figure 33. Figure 34. Figure 35. Figure 36. Figure 37. Figure 38. Figure 39. Figure 40. Figure 41. Figure 42. Figure 43. Figure 44. Figure 45. Figure 46.

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World capture and aquaculture production (FAO, 2007). Inland capture fisheries by continent in 2004 (FAO, 2007). Aquaculture production by regional grouping in 2004 (FAO, 2007). Relative contribution of aquaculture and capture fisheries to food fish consumption (FAO, 2007). GIS assessment of potential areas for production fish farms in Africa. Continuum Aquaculture - Fishery en relation with the investment intensification. The ichthyoregions and the countries.

General implementation plan. Setting of fish ponds: 1. Assessment. Water cycle. Contextual components of the assessment. Setting of fish pond: 2. Selections. Volume of a pond. Water loss through evaporation by weather. Water loss by ground. Flow measurement for small rivers. Measurement of section of the river. Measurement of speed V of the river. Examples of factors that may affect water quality. Secchi disk. Impermeability of clay and sandy soils. Test of the ball (1). Test of the ball (2). Test of soil permeability. Identification of potential water supplies, drainage options, individual valleys, comparison of the various good sites for the installation of ponds, vision of the bottoms (CIRAD). Water supply by gravity. Type of slopes and constraints. Hill slope. Measurement of a slope: Device. Measurement of a slope: Calculation. Example of location of a pond in relation of the house. Setting of fish pond: 3. Ponds. Main components of a pond. Cross section of a ponds. Examples of barrage ponds. Examples of diversion ponds. Disposition of ponds in relation to the topography (CIRAD). Optimization of the surface / work (CIRAD). Example of pond whose shape is adapted to the topography. Disposition and shape of ponds according the slope. Layout of ponds. In series; In parallel. Maximal and minimal depth of a pond. The different points for the management of water by gravity. Level differences. Classical plan a diversion ponds. Examples of diversion fishfarm.

Subsistence fishfarming in Africa

53 54 55 55 57 57 58 60 61 61 64 65 66 66 67 67 67 69 70 70 71 72

Figure 47. Figure 48. Figure 49. Figure 50. Figure 51. Figure 52. Figure 53. Figure 54. Figure 55. Figure 56. Figure 57. Figure 58. Figure 59. Figure 60. Figure 61. Figure 62. Figure 63. Figure 64. Figure 65. Figure 66. Figure 67. Figure 68. Figure 69. Figure 70. Figure 71. Figure 72. Figure 73. Figure 74. Figure 75. Figure 76. Figure 77. Figure 78. Figure 79. Figure 80. Figure 81. Figure 82. Figure 83. Figure 84. Figure 85. Figure 86. Figure 87. Figure 88. Figure 89. Figure 90. Figure 91. Figure 92. Figure 93. Figure 94. Figure 95. Figure 96. Figure 97. Figure 98. Figure 99.

Setting of fish pond: 3. Ponds. 74 Visualization by picketing of the first plan of possible water supply, possible drainage, of differents valley (CIRAD). 75 Preparation of the site of the pond. 76 Cleaning of the site. 76 Water levels differences. 78 Setting of the water supply channel. 79 Transverse profile of the channel. Measure and slope of sides. 79 Channel digging. 80 Setting of draining channel. 81 Level of draining channel. 81 Picketing of the pond and the dikes. 82 Cleaning of the zones where the dikes will be build. 83 Definition of the different types of dikes. 83 Description and proportion of a dike (of 1 m high). 83 Pressure difference on a dike. 84 Dikes. Good high; Dikes too small. 84 Digging of the cut-off trench for clay core. 85 Clay core and saturation of the dikes. 85 High of a dike. Depth; Freeboard; Settlement. 85 High of the structure. 85 Dimension of a dike. 86 Calculation of the slope of the dikes. 87 Construction of the dikes (I). Traditionnal - By blocks. 88 Construction the dikes (II). 88 Preparation of the bottom. 88 The bottom or plate. Direction of the slope and drain setting: In ray; As «fish bones». 89 Bottom drain. 90 Cross cut of a pond at the bottom drain. 90 Cross cut of the inlet of a pond. 91 Pipe inlet. 91 End of bamboo pipe. 91 Gutter inlet. 92 Different types of gutter. 92 Canal inlet. 92 Diagram of an example of sand filter. 93 Turn-down pipe inside pond outlet. 95 Composition of a monk. 96 Position of the monk in the pond. 97 Position of the monk according the downstream dike. 97 Wooden monk. Small and medium size. 98 Wooden pipe. 99 Mould of a monk. Front view; Upper view. 100 Monk. Upper view and example of size. 101 Functioning of a monk. 102 Concrete pipe. Croos cut; Mould; Final pipe. 103 Setting of a pipe overflow. 104 Type of setting basin. Natural; In concrete. 105 Setting basin. Normal; Improved. 106 Setting of a vegetable cover on the dikes. 106 Dikes with plants. Vegetable garden; Small animals; Trees. 107 Type of erosion and soil conservation. Streaming; Infiltration; Protection channel. 107 Fences. In scrubs; In wood or bamboo. 108 Schematic life cycle of a pond. 113

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Figure 100. Figure 101. Figure 102. Figure 103. Figure 104. Figure 105. Figure 106. Figure 107. Figure 108. Figure 109. Figure 110. Figure 111. Figure 112. Figure 113. Figure 114. Figure 115. Figure 116. Figure 117. Figure 118. Figure 119. Figure 120. Figure 121. Figure 122. Figure 123. Figure 124. Figure 125. Figure 126. Figure 127. Figure 128. Figure 129. Figure 130. Figure 131. Figure 132. Figure 133. Figure 134. Figure 135. Figure 136. Figure 137. Figure 138. Figure 139. Figure 140. Figure 141. Figure 142. Figure 143. Figure 144. Figure 145. Figure 146. Figure 147. Figure 148. Figure 149. Figure 150. Figure 151.

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Setting of fish pond: 4. Fishfarming. Trophic pyramids. Differents algae. Aquatic plants. Rotifers. Crustaceans. Insects. Molluscs. Vertebrates other than fish. Beneficial effects of organic fertilizers. Preparation of dry compost. Applying animal manures to a drained pond bottom. Applying animal manures to water-filled ponds that have been stocked (I). Applying animal manures to water-filled ponds that have been stocked (II). Preparation of an anaerobic compost. Compost heap in crib in a pond. Setting of fish pond: 4. Fishfarming and 5. End of cycle. Diagram of a seine. The differents steps to construct a simple seine. Setting of the pole to hold the seine. Construction of a central-bag seine. Manipulation of a seine. Gill nets. Use of a cast net. Different types of dip nets. Differents types of local traps. Fish packing in plastic bags. Sexual differentiation of differents species. Fingerlings produced per fish density in Oreochromis niloticus. Fingerlings produced per females body weight in Oreochromis niloticus. Hapas and cages. Differents systems of reproduction of tilapia in hapas and cages. Live fish storage in hapas or nets. Diagram on the relationships between the stocking density, the instant growth rate (G) and the instant yield per surface unit (Y) with and without complementary feeding. Yield and average weight of Oreochromis niloticus at the harvest in function of initial density. Impact of the presence of a predator (here, Hemichromis fasciatus) in fishponds. Measurement gears. Length - Weight relationships. Harvest of the fish. Examples of way to collect the fish outside of the pond. Setting of fish pond: 5. End of cycle and start again… Fish piping on surface; Dead fish floating on surface. Diseases of fish. Bacterial diseases; External parasites. Example of life cycles of fish disease factors. Structures to facilitate the feeding. Some predators of fish. Differents methods of natural drying of fish. Example of smoking method of fish. Example of salting system. Mosquito and snail. Several human behavior to avoid nearby the ponds. Cleaning of the dikes.

Subsistence fishfarming in Africa

114 115 115 116 116 116 117 117 118 119 123 125 125 125 125 126 128 129 130 130 131 131 133 134 135 135 138 140 141 141 142 143 144 146 147 148 149 150 151 152 154 156 156 157 161 164 166 166 166 172 172 172

APPENDIX Figure 152. Figure 153. Figure 154. Figure 155. Figure 156. Figure 157. Figure 158. Figure 159. Figure 160. Figure 161. Figure 162. Figure 163. Figure 164. Figure 165. Figure 166. Figure 167. Figure 168. Figure 169. Figure 170. Figure 171. Figure 172. Figure 173. Figure 174. Figure 175. Figure 176. Figure 177. Figure 178. Figure 179. Figure 180. Figure 181. Figure 182. Figure 183. Figure 184. Figure 185. Figure 186.

187 Principal terms pertinent to the external morphology of a fish. Different body shapes. Cross-section of body. Jaws. Tooth shapes. Fontanellae. Barbels. Gill slits without opercule; gill arch formed by ceratobranchial, gill rakers, hypobranchial and epibranchial, gill filaments; external gill. Accessory aerial breathing organs. Pair fins. Dorsal fin. Caudal fin. Different types of scales. Lateral line. Location of electric organs. Principal measurements that may be taken on a fish. External features of the Cichlidae. Courtship and spawning in a substrate spawner Cichlidae, Tilapia zillii. Nest of Oreochromis niloticus; Oreochromis macrochir. Courtship and spawning in a mouthbrooder Cichlidae, Haplochromis burtoni from Lake Tanganyika. Mouthbrooding. Example of the life cycle of a maternal mouthbrooding tilapia. Different stages in mouthbrooders. Comparison between fry of substrate spawners and mouthbrooders. Relationship the weight of fish of 20 cm and the size of maturation for Oreochromis niloticus for several geographic location. Size class of Oreochromis niloticus according several geographic location. Comparison of growth rate for different species in natural field by locality. Comparison of growth rate for different species in natural field by species. Relative Fecundity (% of total weight), % of hatching (% total eggs) of Clarias gariepinus, monthly average rainfall and average temperature. Brazzaville. Courtship in Clarias gariepinus. First stages of development for Clarias gariepinus. Several stages of larval development until 17 days. Clarias gariepinus; Heterobranchus longifilis. Compared growth of several African fish species. Growth of Heterotis niloticus and of Lates niloticus. The ichthyoregions and the countries.

207 207 208 208 209 209 210 210 211 211 212 212 213 213 213 215 216 218 219 220 220 221 222 222 224 224 225 225 227 228 229 229 230 238 245

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LIST OF TABLES Part I - INTRODUCTION AND THEORICAL ASPECTS Table I. Table II. Table III. Table IV. Table V.

World fisheries and aquaculture production and utilization, excluding China (FAO, 2007). Origin and number of fish species introductions in Africa. Introduced species with a negative ecological effect recorded. Different levels of intensification of fishfarming systems Characteristics of the two main models of farming towards the various factors of production.

Part II - PRACTICAL ASPECTS Table VI. Table VII. Table VIII. Table IX. Table X. Table XI. Table XII. Table XIII. Table XIV. Table XV. Table XVI. Table XVII. Table XVIII. Table XIX. Table XX. Table XXI. Table XXII. Table XXIII. Table XXIV. Table XXV. Table XXVI. Table XXVII. Table XXVIII. Table XXIX. Table XXX. Table XXXI. Table XXXII. Table XXXIII. Table XXXIV. Table XXXV. Table XXXVI. Table XXXVII.

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Color of the soil and drainage conditions of the soil. Topographical features for ponds. Advantages and disadvantages of the barrage and diversion ponds. Differents shape of a pond of 100 m2. Size of fattening ponds. Resource availability and pond size. Characteristics of shallow and deep ponds. Diversion structures to control stream water levels. Channel dimensions. Examples fo dimension of dikes. Expression of values of slope according the chosen unit. Informations on the dimensions of the monk according the size of the pond. Estimation of the discharge and draining duration of the pond according the diameter of the outlet. Inside dimensions of the monk according the diameter of the pipe. Examples of necessary time for building of ponds (man/day). Approximate output on the works of excavation made by hand. Example of calendar of works to do for the construction of a pond (workers of 400 men per day). Example of calendar according the seasons (15 ponds) in Cameroon. Maximum amount of fresh solid manure per day in 100 m2 pond. Quantity to spread per type of manure. Organic fertilizers commonly used in small-scale fish farming. Particular characteristics of composting methods. Production of Oreochromis niloticus in function of the number of breeders in a pond of 4 ares – 122 farming days. Levels of various nutrients in different species of fish. Relative value of major feedstuffs as supplementary feed for fish. Example of formula for tilapia and catfish farming. Example of quantity of food to give according time per m2 of pond. Feeding rate for tilapia in pond related to the size (table of Marek). Examples of stop feeding per species in function of the temperature Monitoring. x: following; xx: fuller check or major repair; V: In drained pond only. Examples of management for 4 ponds. Harvest after 3 months; After 4 months. Useful life of fish farm structures and equipment (in years, assuming correct utilization)

Subsistence fishfarming in Africa

1 4 10 11 16 17

27 50 54 63 66 68 68 69 78 80 86 87 100 101 101 110 110 111 111 120 120 121 122 141 158 159 160 160 160 161 162 169 170

APPENDIX

187

Table XXXVIII. The tonnage of halieutic products in 2005 per African countries (FAO, 2006). 194 Table XXXIX. The checklist of freshwater species which have been the subject of an introduction in Africa (FAO, 2006; Fishbase, 2006). 195 Table XL. List of species introduced by African countries. 197 Table XLI. List of freshwater fish used in aquaculture by country (FAO, 2006; Fishbase, 2008). 203 Table XLII. Diet of several species of tilapia in natural waters. 217 Table XLIII. Size at sexual maturation, maximale size and longevity of different species of tilapia. 223 Table XLIV. Some characteristics of African countries. 240 Table XLV. Characteristics of ichthyoregions and lakes in Africa. 244 Table XLVI. The ichthyoregions and their repartition by country in Africa. 246 Table XLVII. The genera and species of tilapias recorded by countries. 248

LIST OF SPECIES FILE File I. File II. File III. File IV. File V. File VI. File VII. File VIII. File IX. File X. File XI. File XII. File XIII. File XIV. File XV. File XVI. File XVII. File XVIII. File XIX.

Cichlidae. - Oreochromis andersoni Cichlidae. - Oreochromis aureus Cichlidae. - Oreochromis esculentus Cichlidae. - Oreochromis macrochir Cichlidae. - Oreochromis mossambicus Cichlidae. - Oreochromis niloticus Cichlidae. - Oreochromis shiranus Cichlidae. - Sarotherodon galileus Cichlidae. - Sarotherodon melanotheron Cichlidae. - Tilapia guineensis Cichlidae. - Tilapia mariae Cichlidae. - Tilapia rendalli Cichlidae. - Tilapia zillii Cichlidae. - Hemichromis elongatus and Hemichromis fasciatus Cichlidae. - Serranochromis angusticeps Cichlidae. - Serranochromis robustus Clariidae. - Clarias gariepinus Clariidae. - Heterobranchus longifilis Arapaimidae. - Heterotis niloticus

256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274

Subsistence fishfarming in Africa

x vii

LIST OF PHOTOS Part I - INTRODUCTION AND THEORICAL ASPECTS

1

Part II - PRACTICAL ASPECTS

27

Photo A. Measurement of a slope (DRC) [© Y. Fermon]. Photo B. Example of rectangular ponds in construction laying in parallel (Liberia) [© Y. Fermon]. Photo C. Cleaning of the site. Tree remaining nearby a pond {To avoid}(DRC); Sites before cleaning (Liberia) [© Y. Fermon]. Photo D. Channel during the digging (Liberia) [© Y. Fermon]. Photo E. Stakes during the building of the dikes (Liberia) [© Y. Fermon]. Photo F. Dikes. Slope badly made, destroed by erosion (DRC)[©  Y. Fermon]; Construction (Ivory Coast) [© APDRA-F](CIRAD). Photo G. Example of non efficient screen at the inlet of a pond (Liberia) [© Y. Fermon]. Photo H. Example of filters set at the inlet of a pond in Liberia [© Y. Fermon]. Photo I. Mould and monks (Guinea). The first floor and the mould; Setting of the secund floor [© APDRA-F] (CIRAD). Photo J. First floor of the monk associated with the pipe (Guinea) [© APDRA-F](CIRAD). Photo K. Top of a monk (DRC)[© Y. Fermon]. Photo L. Building of a pipe(Guinea) [© APDRA-F](CIRAD). Photo M. Setting of a fences with branches (Liberia) [© Y. Fermon]. Photo N. Compost heap. [Liberia © Y. Fermon], [© APDRA-F](CIRAD). Photo O. Use of small beach seine (Liberia, Guinea, DRC) [© Y. Fermon]. Photo P. Mounting, repair and use of gill nets (Kenya, Tanzania) [© Y. Fermon]. Photo Q. Cast net throwing (Kenya, Ghana) [© F. Naneix, © Y. Fermon]. Photo R. Dip net (Guinea) [© Y. Fermon]. Photo S. Traps. Traditionnal trap (Liberia); Grid trap full of tilapia (Ehiopia) [© Y. Fermon]. Photo T. Fish packing in plastic bags (Guinea, (Ehiopia) [© Y. Fermon, © É. Bezault]. Photo U. Hapas in ponds (Ghana) [© É. Bezault]. Photo V. Concrete basins and aquariums (Ghana) [© Y. Fermon].

56 68

100 102 102 103 108 126 132 132 134 135 136 138 143 145

APPENDIX

187

77 80 82 89 93 93

Photo W. Nests of Tilapia zillii (Liberia) [© Y. Fermon]. 219 Photo X. Claroteidae. Chrysichthys nigrodigitatus [© Planet Catfish]; C. maurus [© Teigler - Fishbase]; Auchenoglanididae. Auchenoglanis occidentalis [© Planet Catfish]. 232 Photo Y. Schilbeidae. Schilbe intermedius [© Luc De Vos]. 233 Photo Z. Mochokidae. Synodontis batensoda [© Mody - Fishbase]; Synodontis schall [© Payne - Fishbase]. 234 Photo AA. Cyprinidae. Barbus altianalis; Labeo victorianus [© Luc De Vos, © FAO (drawings)]. 235 Photo AB. Citharinidae. Citharinus gibbosus; C. citharus [© Luc De Vos]. 235 Photo AC. Distichodontidae. Distichodus rostratus; D. sexfasciatus [© Fishbase]. 236 Photo AD. Channidae. Parachanna obscura (DRC) [© Y. Fermon]. 236 Photo AE. Latidae. Lates niloticus [© Luc De Vos]. 237

xviii

Subsistence fishfarming in Africa

Part I

INTRODUCTION AND THEORICAL ASPECTS

Contents • Fishfarming: Aim and issues • Type of fishfarming • Biogeography and fish species • Summary

Subsistence fishfarming in Africa

1

CONTENTS - PART I Chapter 01 - FISHFARMING: AIM AND ISSUES

3

I. WHY?

3

II. PRESSURE ON THE RESOURCES

6



II.1. Modifications of the habitat

6



II.2. Water pollution

8



II.3. Fisheries impact

9



II.4. Introductions

9

III. INTERNATIONAL ASPECTS

12

IV. OBJECTIVE OF FISHFARMING

13

Chapter 02 - TYPE OF FISHFARMING

15

I. VARIOUS TYPES OF FISHFARMING

15

II. SOME HISTORY…

17

III. A FISHFARMING OF SUBSISTENCE: GOAL AND PRINCIPLE

17

IV. POLYCULTURE VS MONOCULTURE

18

Chapter 03 - BIOGEOGRAPHY AND FISH SPECIES

21

I. GEOGRAPHY

21

II. THE SPECIES

21

I.1. The Cichlidae

22

II.2. The Siluriformes or catfishes

23

II.3. The Cyprinidae

23

II.4. Other families and species

24

SUMMARY

Cover photo: Ö Ö Children fishing fingerlings in river for the ponds, Liberia, ASUR, 2006 - © Yves Fermon

2

Subsistence fishfarming in Africa

25

Chapter 01

FISHFARMING: AIM AND ISSUES I. WHY? Fisheries and aquaculture contribute to the food security primarily in three ways: ÖÖ To increase the food availabilities, ÖÖ To provide highly nutritive animal proteins and important trace elements, ÖÖ To offer employment and incomes which people use to buy of other food products. A little more than 100 million tons of fish are consumed worldwide each year, and ensure to 2.5 billion of human at least 20% their average needs per capita of animal proteins (Figure 1 below). This can range to over 50% in the developing countries. In some of the zones most affected by food insecurity - in Asia and Africa, for example - the fish proteins are essential because, they guarantee a good part of the already low level of needs of animal proteins. Approximately 97% of the fishermen live in the developing countries, where fishing is extremely important. Fish production in Africa has stagnated over the past decade, and availability of fish per capita decrease (8.8 kg in the 90s, about 7.8 kg in 2001) (Table I, p. 4). Africa is the only continent where this tendency is observed, and the problem is that there do not exist other sources of proteins accessible to all. For a continent where food security is so precarious, the situation is alarming. Even if Africa has the lowest consumption of fish per capita in the world, the marine and inland water ecosystems are very productive and sustain important fisheries which recorded a rise in some countries. With a production of 7.5 million tons in 2003 and similar levels in previous years, the fish ensures 50% or more of the animal protein contributions of many Africans - i.e. the second rank after Asia. Even in sub-Saharan Africa, the fish ensures nearly 19% of the animal protein contributions of the population. This constitutes an important contribution in an area afflicted by hunger and malnutrition. But whereas the levels of production of fishings are stabilized, the population continues to grow. With the sight of the forecasts of UN on the population trends and the evaluations available on the

Millions tonnes 140 China World excluding China

120 100 80 60 40 20 0 50

55

60

65

70

75

80

85

90

95

00

04

Years Figure 1. World capture and aquaculture production (FAO, 2007).

Subsistence fishfarming in Africa

3

Table I. World fisheries and aquaculture production and utilization, excluding China (FAO, 2007). 2000

2001

2004

2005

Capture

6.6

6.7

6.5

6.6

6.8

7.0

Aquaculture

6.0

6.5

7.0

7.6

8.3

8.8

Total

12.6

Capture

72.0

13.3

13.5

14.2

15.1

15.8

69.8

70.2

67.2

71.3

69.7

Aquaculture

4.9

5.3

5.6

6.1

6.6

6.6

Total

76.9

75.2

75.8

73.3

77.9

76.3

Capture

78.6

76.6

76.7

73.8

78.1

76.7

Aquaculture

10.9

11.9

12.6

13.8

14.9

15.4

Total

89.5

88.4

89.3

87.5

93.0

92.1

Human consumption

63.9

65.7

65.7

67.5

68.9

69.0

Non-food uses

25.7

22.7

23.7

20.1

24.0

23.1

Population (billions)

4.8

4.9

5.0

5.0

5.1

5.1

Per capita food fish supply (kg)

13.3

13.4

13.3

13.4

13.5

13.4

Production Inland

Marine

Total

2002

2003

(million tonnes)

Utilization

future tendencies of halieutic production, only to maintain the fish consumption per capita of Africa on his current levels, the production should increase of more than one third during the 15 next years, which is a challenge. The situation was partly aggravated by the significant increase in exports, and harvests of non-African fleets operating in the area under the fisheries agreements. Fish coastal resources are already heavily exploited and marine capture fisheries would be difficult to produce more, even through massive investments. Difficult to reduce exports, considering the need for foreign currencies in the countries concerned. After a slight downturn in 2002, the total world catch in inland waters is again increase in 2003 and 2004 to reach 9.2 million tonnes during the past year. As previously, Africa and Asia represent approximately 90 percent of the world total and their respective shares are relatively stable (Figure 2, p. 5). The fisheries, however, seem in crisis in Europe where the total catch has dropped by 30% since 1999. Game fishing represents a substantial part of the catch. The statistics of developed countries on catches in inland waters, published by FAO, are generally based on information provided by national correspondents, and the total catch may vary significantly depending on whether they take into account or not catch of game fisheries. In Africa - as in the world in general - aquaculture will play an important role. Globally, aquaculture accounts for about 30% of world supplies of fish. The aquacultural production in Africa accounts for only 1.2% of the world total (Figure 3, p. 5). The aquaculture in Africa today is primarily an activity of subsistence, secondary and part-time, taking place in small-scale farmings. This African production primarily consists of tilapia (15 000 T), of catfishes (Clarias) (10 000 T) and of common carps (5 000 T). It is thus about a still embryonic activity and which looks for its way from the point of view of the development for approximately half a century. The aquaculture yet only contributes most marginally to the proteins supply of water origin of the African continent where the total halieutic production (maritime and inland) was evaluated in 1989 to 5.000.000 T. The part of fish in the proteins supply is there nevertheless very high (23.1%), slightly less than in Asia (between 25.2 and 29.3%), but far ahead of North America (6.5%) or Western Europe (9.4%), world mean of

4

Subsistence fishfarming in Africa

Oceania

0.2%

North and Central America

2.0%

Europe

3.5%

South America

4.9%

Africa 24.7% Asia 64.8%

Figure 2. Inland capture fisheries by continent in 2004 (FAO, 2007). 16.5% (Figure 4, p. 6). Aquaculture in Africa thus remains limited. There are several reasons for this, but the most important is that the sector is not treated as a business enterprise, in a viable and profitable point of view.

Quantity Asia (excluding China)  and the Pacific  21.92%

Western Europe

3.54%

Latin America and the Caribbean 2.26% 8.51% China 69.57%

North America

1.27%

Near East and North Africa

0.86%

Central and Eastern Europe

0.42%

Sub-Saharan Africa

0.16%

Western Europe

7.72%

Value Asia (excluding China)  and the Pacific  29.30%

Latin America and the Caribbean 7.47% 19.50% China 51.20%

North America

1.86%

Near East and North Africa

1.19%

Central and Eastern Europe

0.91%

Sub-Saharan Africa

0.36%

Figure 3. Aquaculture production by regional grouping in 2004 (FAO, 2007).

Subsistence fishfarming in Africa

5

Fishery food supply (kg/capita) 30 Aquaculture Capture

25 20 15 10 5 0

70

79

88 World

97

04

70

79

88 China

97

04

70

79 88 97 World excluding China

04

Years Figure 4. Relative contribution of aquaculture and capture fisheries to food fish consumption (FAO, 2007). But this does not mean ignoring the need for fisheries management. Better management of marine and inland fisheries in Africa contribute to the safeguarding of these important sectors of food production. Aquaculture is not intended to replace fishery but to supplement the intake of animal protein.

II. PRESSURE ON THE RESOURCES The continental aquatic environments are particularly affected by the human activities: modification or disappearance of the habitats generally resulting from water development (dams), pollution of various origins, overexploitation due to fishing as well as the voluntary or not introductions of nonnative species. The consequences, amplified at the present time by the increase in population and an increasingly strong pressure on the natural resources, endanger fish fauna quite everywhere in the world. Long enough saved, Africa suffers in its turn these impacts, even if pollution for example, remains still relatively limited in space.

II.1. MODIFICATIONS OF THE HABITAT

The alteration of habitat is one of the most important threats to aquatic life. The changes that may have two distinct origins which generally interfere nevertheless: 99 Climate change with its impact on water balance and hydrological functioning of hydrosystems; 99 The changes due to man both in the aquatic environment and its catchment area.

II.1.1. CLIMATE CHANGES

The existence of the surface aquatic environments depends closely on the contributions due to the rains, and thus on the climate. Any change in climate will have major consequences in terms of water balance that will lead by example by extending or reducing aquatic habitat. A spectacular event is the Lake Chad area of which strongly decreased during the 1970s due to a period of dryness in the Sahel. We know that the climate has never been stable on a geological and aquatic environments have always fluctuated without that man can be held responsible (the phenomenon «El Niño» for example). But we also know that man can act indirectly on the climate, either locally by deforestation, or at global level by the emission of certain gases in the «greenhouse effect». These last years, world opinion has been alerted to a possible warming of the planet which would be due to the increase in air content of carbon dioxide, methane and chlorofluorocarbons (CFCs), whose emission mass is

6

Subsistence fishfarming in Africa

linked to industrial activities. If it is not clear to what extent and how fast will this warming, it may be feared that these climate changes occur in the coming decades, resulting in a change in rainfall in some regions of the world. Besides small predictable consequences on the water (increase or decrease in local rainfall), we can also expect an increase in sunshine and temperature, changes in the distribution of vegetation, at an elevation sea levels. Although it is still impossible at the local level to assess the consequences of the changes announced, it seems clear, whatever the magnitude of the phenomenon that aquatic fauna as a whole will be the first affected..

II.1.2. DEVELOPMENTS

The various uses of water for agriculture, energy production, transport, domestic needs, are at the base of many hydrological building facilities. These constraints affect the water balance but also, directly or indirectly, the aquatic habitats.

■■ Dams

Large hydroelectric dams are expensive constructions, whose economic interest is often controversial and whose environmental impact is important. When we block a stream to create a dam, we provoke numerous modifications of the environmental habitat and the fish community and we disrupt the movements of migratory fishes.

■■ Development of rivers

The development facilities with the construction of dykes, the rectification of water course, the construction of locks for navigation ... are still limited in Africa, but we can nevertheless give some examples of projects that have changed quite considerably natural systems. In the valley of Senegal, for example, many work was completed for better managing the water resources of the river and to use them at agricultural ends. The purpose of the construction of a dam downstream nearby the estuary (dam Diama) is to prevent the coming back of marine water in the lower course of the river during the dry season, whereas the dam Manantali located upstream makes it possible to store great quantities of water at the time of the overflood and to restore them according to the request to irrigate vast perimeters. All the water resources of the valley of Senegal is now partially under control, but the water management becomes complex to deal with sometimes conflict demands in term of uses.

■■ Reduction of floods plains and wetlands

The wetlands are often considered as fertile areas favourable for agriculture. Everywhere in the world the development projects and in particular the construction of dams had an significant impact on the hydrosystems by reducing sometimes considerably the surface of the floodplains which are places favourable for the development of juveniles of many fish species..

■■ Changes in land use of the catchment area

The quantity and the quality of the contributions out of surface water to aquatic ecosystems depend on the nature of the catchment area and its vegetation. However the disappearance of the forests, for example, whether to make of them arable lands or for the exploitation of wood for domestic or commercial uses, has, as an immediate consequence, an increase of the soil erosion and water turbidity, as well as a modification of the hydrological mode with shorter but more brutal runoff resulting from a more important streaming. The problem of the deforestation concerns Africa in general and the available information shows that the phenomenon is worrying by its scale. Thus, it was discovered in Madagascar that the deforestation rate was 110 000 ha per year for 35 years, and erosion rate of 250 tonnes of soil per hectare have been reported. In the Lake Tanganyika drainage, deforestation is massive too. The erosion on the slopes has resulted in significant contributions to the lake sediment and changes in wildlife in some coastal areas particularly vulnerable. If current trends continue, the figures are coming with an estimated worrying that at this rate, 70% of forests in West Africa, 95% of those from East Africa and 30% of the congolese coverage would have to disappear by the year 2040. The increase in the suspended solid in water, and silt deposits in lakes and rivers, has many effects on aquatic life. There are, of course, reduce the transparency of its waters with implications for the planktonic and benthic photosynthesis. The suspension elements may seal the branchial system of fish or cause irritation and muddy deposits deteriorate the quality of substrates in breeding areas.

Subsistence fishfarming in Africa

7

II.2. WATER POLLUTION

If water pollution has long appeared as a somewhat secondary phenomenon in Africa, it is clear that it is increasingly apparent in recent years. In general, however, lack of data and more detailed information on the extent of water pollution in Africa.

II.2.1. EUTROPHICATION OF WATER

The nutritive elements (phosphates, nitrates) are in general present in limited quantities in the aquatic environments, and constitute what one calls limiting factors. Any additional contribution of these elements is quickly assimilated and stimulates the primary production. When the natural cycle is disturbed by the human activities, in particular by the contributions in manure, detergents, waste water in general, excesses of phosphates (and to a lesser extent of nitrates) is responsible for the phenomenon of eutrophication. This phenomenon results in an excessive proliferation of algae and/ or macrophytes, and a reduction in the water transparency. The decomposition of this abundant organic matter consumes much oxygen and generally leads to massive mortalities of animal species per asphyxiation. Eutrophication also has as a result to involve strong variations of the dissolved oxygen concentration and pH during the day. In the lakes, the phenomenon of “bloom” (the “fleur d’eau” of the French speaking) is one of the manifestations of eutrophication. Eutrophication of Lake Victoria during the last 25 years is fairly well documented. Increased intakes of nutrients to the lake is the result of increasing human activities in the catchment area of the lake: increased urbanization, use of fertilizers and pesticides for the crops, use of pesticides for control of tsetse flies ...

II.2.2. PESTICIDES

In the second half of the twentieth century the use of chemical pesticides has become widespread in Africa, as elsewhere in the world to fight against both the vectors of major diseases and pests of crops. The range of products used is very large and, if some have a low toxicity towards aquatic organisms, many are xenobiotics, ie substances that have toxic properties, even if they are present in the environment at very low concentrations. This is particularly true for pyrethroids (permethrin, deltamethrin) but especially for organochlorines (DDT, dieldrin, endrin, endosulfan, malathion, lindane), which, in addition to their toxicities have important time remanence, this which accentuates their accumulation and thus their concentration in food webs.

II.2.3. HEAVY METALS

Under the term of “heavy metals”, one generally includes several families of substances: 99 Heavy metals in the strict sense, with high atomic mass and high toxicity, whose presence in small amounts is not necessary to life: cadmium, mercury, lead… 99 Metals lower atomic mass, essential for life (trace elements), but quickly become toxic when their concentration increases: copper, zinc, molybdenum, manganese, cobalt… Heavy metals usually occur at very low concentrations in natural ecosystems but human activities are a major source of pollution. Heavy metals come from the agricultural land and water systems by intentional inputs of trace elements and pesticides, discharge from refineries or factories treating non-ferrous metals (nickel, copper, zinc, lead, chromium, cadmium ...), discharges from tanneries (cadmium, chromium) or paper pulp (mercury). It must be added the impact of atmospheric pollution related to human activities (including industrial), and domestic and urban effluents (zinc, copper, lead). Mercury pollution may have originated in industrial uses (paper industry), the exploitation of gold deposits, the use of organomercury fungicides. The problems associated with heavy metal contamination resulting from the fact that they accumulate in the organisms where they may reach toxic levels.

II.2.4. BIO-ACCUMULATION

An alarming phenomenon with certain contaminants, including heavy metals or pesticides, is the problem of bioaccumulation which leads to the accumulation of a toxic substance in an organism, sometimes in concentrations much higher than those observed in the natural environment. This concerns various contaminants.

8

Subsistence fishfarming in Africa

Organisms with concentrated pollutants can enter to turn the trophic chain, and if the product is not degraded or removed, it will concentrate more and more with each trophic chain link, eg from algae to ichthyophagous birds. This phenomenon which is called biomagnification, shows that the pollution of environment by substances that are measured in very small quantities in water, can have unexpected consequences on higher consumer.

II.3. FISHERIES IMPACT

The impact of fishing on fish populations appears primarily, according to the fishing gears used, by a selective pressure on certain species, either on adults, or on juveniles. It is frequently thought that fishing alone, when used with traditional gear, can not be held responsible for the disappearance of fish species. Indeed, it is not easily conceivable that one can completely eliminate a population by captures made as a blind man contrary with what can occur for hunting. However, a pressure associated with changes in habitat can lead fairly rapidly declining species. The effects of fishing are particularly sensitive to large species with low reproductive capacity. One quotes for example the quasi-disappearance of the catfish Arius gigas in the basin of Niger. In this species, the male is buccal incubator of a few large eggs. In the early 20th century, it referred to the capture of specimens of 2 meters long, while since 1950 the species seemed to become very rare. One of the clearest fishing effect is showned in the population demography, with the reduction in the mean size of species and the disappearance of large individuals. Indeed, if the fishery usually starts with large gear mesh, the size of these decreases as catches of large individuals are rare. In some cases, the mesh size is so small that gear catch immature individuals and populations of species that can not reproduce collapsing dramatically. In the lake Malombe for example, the fishing of Oreochromis (O. karongae, O. squamipinnis) was done with gillnets. It has been observed in the 1980s increased fishing with small mesh seines, and a parallel collapse of the Oreochromis fishery. This mode of exploitation would be responsible also for the disappearance of nine endemic species of large size of Cichlidae.

II.4. INTRODUCTIONS

While for centuries introductions of fish species have been promoted across the world to improve fish production, they have become in recent decades the subject of controversy among scientists and managers of aquatic environments. Indeed, the introduction of new species can have significant effects on indigenous fish populations. The introduction of new species in an ecosystem is sometimes the cause of the phenomena of competition that may lead to the elimination of native species or introduced species. But there may also have indirect changes, which are generally less easy to observe, through the trophic chains. To correctly interpret the impacts of introductions, it is necessary to distinguish several levels from intervention: 99 That of the transplantation of species of a point to another of the same catchment area; 99 That of the introduction of alien species to the basin but coming from the same biogeographic zone; 99 That of the introduction of species coming from different biogeographic zones, even from different continents.

II.4.1. COMPETITION WITH THE INDIGENOUS SPECIES

Introduced species may compete with native species, and possibly eliminate them. This is especially true when introducing predator species. One of the most spectacular cases is that of the introduction into Lake Victoria of the Nile Perch, Lates niloticus, a piscivorous fish being able to reach more than 100 kg. To some scientists, this predator is the cause of the decline and likely extinction of several species belonging to a rich endemic fauna of small Cichlidae which he fed on. `

Subsistence fishfarming in Africa

9

II.4.2. EFFECT ON AQUATIC ECOSYSTEM

The introduction of a predator in an aquatic ecosystem can affect the biological functioning of the system through the trophic chains. Using the example of Lake Victoria, the Nile perch would be responsible for the virtual disappearance in the 80s of the group of detritivores / phytoplanctivore of haplochromine (Cichlidae endemic), and the group zooplanctivores which were respectively 40 and 16% of the biomass of demersal fish. Detritivorous have been replaced by indigenous shrimp Caridina nilotica, and by the zooplanctivores Cyprinidae pelagic Rastrineobola argentea, these latter two species have become the mean food of the Nile perch after the disappearance of the haplochromine.

II.4.3. HYBRIDIZATIONS

The introduction into the same water body of related species that do not normally live together may result in hybridization. Species of tilapia, in particular, are known to hybridize, which can cause genetic changes for the species surviving. For example, in Lake Naivasha, Oreochromis spilurus introduced in 1925 was abundant in the years 1950 and 1960, and then hybridize with O. leucostictus introduced in 1956. This resulted in the disappearance of O. spilurus and hybrids. The disappearance of the species O. esculentus and O. variabilis, endemic to Lakes Victoria and Kyoga, could be due to hybridization and/or competition with introduced species (O. niloticus, T. zillii). Hybrids O. niloticus x O. variabilis were found in Lake Victoria. If we consider the introductions and movements of fish in Africa, everything and anything has been done (Annexe 02, p. 197, Table II, p. 10 and Table III, p. 11). First by the colonialists who introduced the species they used as trout or carp. Then many species have been transplanted from country to country in Africa to test for fishfarming, as many tilapia. This up to nonsense as to bring strains of Nile Tilapia (Oreochromis niloticus niloticus) or Mossambic Tilapia (O. mossambicus) in areas where there were native strains. For example, the famous strain of “Bouaké” in Ivory Coast which would be, in fact, a mixt of several broodstocks, was introduced into several countries in which the species O. niloticus is native. Same thing on the strain of Butaré, in Rwanda, where it would seem that it is a stock brought back the first time to the United States by a research institute and brought back afterwards to Rwanda!! (Lazard, pers. com.). Elements are given on the distribution of the species in Appendix 05, p. 255.

ÖÖ In this case, it is to pay attention to the provenance of the fish to use and watershed where action is taken, more so, because of the risks incurred by the introduction of fish and national and international legislative aspects concerning biodiversity.. ÖÖ This is not because a species has already been introduced in the intervention area, that it is necessary to use it.

Table II. Origin and number of fish species introductions in Africa.

10

Coming from

Number

Africa

206

North America

41

South America

3

Asia

58

Europe

92

Unknown

128

Total

528

Subsistence fishfarming in Africa

Table III. Introduced species with a negative ecological effect recorded. ENE= Number of country which have recorded an Ecological Negative Effect.

Order

Family

Clupeiformes

Clupeidae

Cypriniformes

Cyrpinidae

Species (n = 39) Limnothrissa miodon Aristichthys nobilis Carassius auratus auratus Carassius gibelio

Clariidae

Loricariidae Esociformes

Esocidae

Salmoniformes

Salmonidae

Centrarchidae

Gobiidae

Cichlidae

Goldfish

9

Prussian carp

4 5

Vairon

Sharpbelly

3

Carpe argentée

Silver carp

9

Pimephales promelas

Tête de boule

Fathead minnow

3

Pseudorasbora parva

Pseudorasbora

Stone moroko

12

Ameiurus melas

Poisson chat

Black bullhead

8

Ameiurus nebulosus

Poisson chat

Brown bullhead

3

Clarias batrachus

Poisson chat marcheur

Walking catfish

5

Clarias gariepinus

Poisson chat nord africain

North African catfish

6

Pléco

Vermiculated sailfin catfish

3

Pterygoplichthys disjunctivus Esox lucius Oncorhynchus mykiss

Brochet

Northern pike

5

Truite arc-en-ciel

Rainbow trout

21 12

Truite de mer

Sea trout

Saumon de fontaine

Brook trout

5

Athérine d’Argentine

Pejerrey

4

Gambusia affinis

Gambusie

Mosquitofish

9

Poecilia latipinna

Molly

Sailfin molly

3

Guppy

Guppy

8

Porte-épée vert

Green swordtail

4

Gymnocephalus cernuus

Grémille, Goujonperche

Ruffe

3

Perca fluviatilis

Perche commune

European perch

3

Perche soleil

Pumpkinseed

9

Lepomis macrochirus

Crapet arlequin

Bluegill

6

Micropterus dolomieu

Black-bass à petite bouche

Smallmouth bass

3

Micropterus salmoides

Black-bass à grande bouche

Largemouth bass

13

Neogobius melanostomus

Gobie à taches noires

Round goby

6

Dromeur chinois

Chinese sleeper

4

Perche du Nil

Nile perch

4

Tilapia du Mozambique

Mozambique tilapia

21

Tilapia du Nil

Nile tilapia

16

Parachromis managuensis

Cichlidé de Managua

Guapote tigre

3

Sarotherodon melanotheron melanotheron

Tilapia à gorge noire

Blackchin tilapia

3

Tilapia rendalli

Tilapia à ventre rouge

Redbreast tilapia

3

Tilapia zillii

Tilapia à ventre rouge

Redbelly tilapia

3

Lepomis gibbosus

Odontobutidae Perccottus glenii Latidae

Poisson rouge Carpe de Prusse

22

Xiphophorus hellerii Percidae

3

Grass carp

Poecilia reticulata Perciformes

Bighead carp

Common carp

Atherinopsidae Odontesthes bonariensis Poeciliidae

3

Amour marbré, à grosse tête

Carpe herbivore

Salvelinus fontinalis Cyprinodontiformes

Lake Tanganyika sardine

Carpe commune

Salmo trutta trutta Atheriniformes

Sardine du Tanganyika

Ctenopharyngodon idella

Hypophthalmichthys molitrix

Ictaluridae

English common ENE name

Cyprinus carpio carpio Hemiculter leucisculus

Siluriformes

French common name

Lates niloticus Oreochromis mossambicus Oreochromis niloticus niloticus

Subsistence fishfarming in Africa

11

III. INTERNATIONAL ASPECTS The Convention on Biological Diversity (CBD), known informally as the Biodiversity Convention, is an international treaty that was adopted at the Earth Summit in Rio de Janeiro in June 1992. The Convention has three main goals: 1. Conservation of biological diversity (or biodiversity); 2. Sustainable use of its components; 3. Fair and equitable sharing of benefits arising from genetic resources. In other words, its objective is to develop national strategies for the conservation and sustainable use of biological diversity. It is often seen as the key document regarding sustainable development.The Convention was opened for signature on 5 June 1992 and entered into force on 29 December 1993. It has been signed in December 1993 by 168 countries. Somalia is the only of the 53 African countries which have not signed. The convention recognized for the first time in international law that the conservation of biological diversity is «a common concern of humankind» and is an integral part of the development process. The agreement covers all ecosystems, species, and genetic resources. It links traditional conservation efforts to the economic goal of using biological resources sustainably. At the meeting in Buenos Aires in 1996, the focus was on the local knowledge. Key actors, such as local communities and indigenous peoples, must be taken into account by the States, which retain their sovereignty over the biodiversity of their territories they must protect. It establishes the principles for the fair and equitable sharing of benefits arising from the use of genetic resources, including those intended for commercial use. It also covers the area of biotechnology through its Cartagena Protocol on Biosafety in 2001, addressing issues of technological development, benefitsharing and biosafety. The convention reminds decision-makers that natural resources are not infinite and sets out a philosophy of sustainable use. While past conservation efforts were aimed at protecting particular species and habitats, the Convention recognizes that ecosystems, species and genes must be used for the benefit of humans. However, this should be done in a way and at a rate that does not lead to the long-term decline of biological diversity.

ÖÖ Above all, the Convention is legally compulsory, the member states are forced to implement its mesures. ÖÖ This means to respect these mesures in the projects on the field while avoiding up to have an effect on the environment that may affect biodiversity. If so, this could turn against the organism responsible for the project despite the intentions and the tacit agreement of local and regional authorities.

12

Subsistence fishfarming in Africa

IV. OBJECTIVE OF FISHFARMING It is not necessary that pisciculture is made at the expense of the natural environments. A fishfarming causing of the organic matter rejections or being implied in the introduction of an alien species, can involve an important ecological change and, therefore, to have serious effects on the animal protein contribution. Indeed, there exists a big risk of reduction of the captures of fishings whereas fishfarming is made for an additional contribution, not for a replacement of the available resource, in the case, of course, where this one is present. As shown in the Figure 5, p. 14, in addition to the strictly desert zones, where, for lack of water, fishfarming can be difficult, it is possible to produce fish almost everywhere in Africa.

ÖÖ The objective of the fishfarming is not to replace fisheries but to supplement its contributions in maintaining the current level of fish consumption, regarding the increase of world population. However, this goal must be pursued in respect of environmental, consumer health and bioethics.

Subsistence fishfarming in Africa

13

Constraint Unsuitable Moderatly suitable Suitable Very suitable No data

Figure 5. GIS assessment of potential areas for production fish farms in Africa.

14

Subsistence fishfarming in Africa

Chapter 02

TYPE OF FISHFARMING According to FAO (1997), aquaculture is defined as: « The culture of aquatic organisms including fish, molluscs, crustaceans and aquatic plants. The term culture implies some form of intervention in the rearing process to enhance production, such as restocking at regular intervals, food, protection against predators ... This culture also implies individual or legal ownership of the breeding stock. From the viewpoint of statistics, aquatic organisms harvested by an individual or legal person who had owned throughout their breeding period are products of aquaculture. On the other hand, publicly aquatic organisms used as a common property resource, with or without appropriate licenses are to be considered as fishery products » In this case, we are interested in the culture of fishes or fishfarming.

I. VARIOUS TYPES OF FISHFARMING The types of fishfarming depend mainly on the investment, the quantity of fish produced per unit of area and on the destination of the products. They are generally characterized by their degree of intensification, itself definite according to the feeding practices; the external food supply represents indeed in general more than 50% of the total costs of production in the intensive systems. However the intensification involves many other factors of production, like water, land, capital and labor. The various types of systems of fish production are presented in Table IV, p. 16 according to their degree of intensification. A first classification can be established in the following way: 99 Extensive fishfarming systems, based on the natural productivity of the pond or on the structure of farming, without or with very few inputs. Generally, there are farming installed in basins or medium or large ponds. Food is quite simply provided by the natural productivity of the water, which is very little or slightly favourably increase. The external contributions are limited, the costs remain weak, the funded capital is reduced, the quantities of fish produced per unit of area are low. In short, the control of the factors of production remains on a low level. The systems of integration of rice and fishfarming belong to this extensive category, since the fish profits from the inputs brought for the culture of rice. 99 Semi-intensive fishfarming systems are based on the use of a fertilization or the use of a complementary food, knowing that a large part of the food of fish is provided in situ by natural food. The farming associated with poultry-fish or pig-fish belong typically to this type of fishfarming. 99 Superintensive and intensive systems and, in which all the nutritional needs for fish are satisfied by the inputs, with small or very few nutritional contributions resulting from the natural productivity from the basin or the water in which the fish is produce (lake, river). The food used in these systems of farming is generally rich in proteins (25 to 40 %); it is consequently expensive. The intensive fishfarming means that the quantities of fish produced per unit of area are high. To intensify the farming and to improve the conditions, the factors of production (food, water quality, quality of fingerlings) must be controlled. The cycle of production requires a permanent follow-up. The principal infrastructures of this type of fishfarming the enclosures or the cages, with very high renewal rates of water. The evolution of an extensive system to an intensive system which are the two extremes, is linked to the evolving global investment from low to important. Another typology of fish production systems can be proposed, based on a differentiation between: 99 The models where the food is coming essentially (or only) from the ecosystem (case of the ecosystem pond), systems called production fishfarming. The management of this type involves the fertilization or the complementary food, with the implementation of the polyculture. There is a strong interaction between the density of fish, the final individual weight of fish (growth rate) and the performance which must be managed carefully. It is thus a question of recreating an ecosystem where the

Subsistence fishfarming in Africa

15

Table IV. Different levels of intensification of fishfarming systems. Density of fish at stocking

< 0.1 m-2 0.1 to 1 m-2

1 to 5 m-2

5 to 10 m-2

10 to 100 m-2

Farming structure

Pond, small dam, pool

Pond

Pond, cage

Ponds, pools, raceways, cages

15 to 50

50 and more to 200 kg.m-3

Generally, monoculture

Monoculture

Yield (t/ha/year)

0 - 0.3

0.3 - 1

Fish intitial stock

Mainly polyculture

Inputs

Low or no inputs

Dayly rate of water renewal (%)

Naturel contribution None

Sometimes <5

Intensification level

Extensive

Models

Semi-fishfarm

1 to 5

5 to 15

Polyculture

Fertilizers, macrophytes, simple food (bran, Composed food oilcake) Compensation for losses

Equilibrate food with fish meal, extruded, antibiotic

Ventilation, Ventilation/oxygenation water circulation

<5

5 to 30

> 30

Semi-intensive

Intensive

Super intensive

Production fishfarm

Transformation fishfarm

fish are at the end of the trophic chain. 99 The models where the food is entirely exogenous and that the fish feeds entirely with artificial food, usually in the form of granules and having a very high proportion of fishmeal, systems called transformation fishfarming. The management of this second type is primarily based on monoculture, of the high densities of fish and an artificial food rich in proteins. The decision to implement one of these types of fishfarming depends on many factors which are presented in Table V, p. 17. Another typology of African piscicultures resulted in classifying them in four categories, on the basis of socio-economic criterion and not of the level of intensification of the production: 99 The subsistence or self-consumption farming (of which the product is for the provisioning of the fishfarmer and his family), where the techniques implemented, qualified as extensive ones, correspond to a low level of technicality. 99 The artisanal or small scale fishfarming, which develops primarily in suburban zone and which offers the best environment for the supply of inputs and the marketing of fish. 99 The fishfarming of the type “channel” characterized by the segmentation of the various phases of farming, mainly in cages and enclosure. 99 The industrial fishfarming, characterized by production units of great dimension whose objective is strictly economic, even financial, in opposition to the three preceding forms where fishfarming constitutes not only production tools, but also development tools. For a long time it was allowed that the practice of production fisfharming required only one low level of technicality on behalf of the fishfarmers compared to system baseds on an exogenic food. Reality is not that simple. The intensive fishfarming models, based on advanced technologies, are ultimately perhaps easier to transfer as their main components are well defined and that the farmer is led in an environment where the not controlled natural components interfere little (farmer in cages in lakes and rivers) or at all (raceways, vats). The production costs and the outputs are higher in the intensive systems. But there exist important obstacles, in any case initially: ¾¾ The level of risk, in terms of diseases of fish, is important in the intensive systems compared to the extensive systems, ¾¾ The starting investment is very high and is productive only after several years, which implies, ¾¾ Training of technicians and that takes time with the professionalism,

16

Subsistence fishfarming in Africa

Table V. Characteristics of the two main models of farming towards the various factors of production. The symbol – means that the production factor is a constraint for the establishment of the fishfarming involved; the symbol + an asset. Production factor

Transformation fishfarming

Production fishfarming

Land Water Environnemental impact Working capital Labor force (per kg of produced fish) «Food» Technicity Risk Production costs Yield Plasticity (ex: Juveniles production)

+ discharge – –

– surface + +

+

+

– – – – +

+ – + + –

–

+

¾¾ T he establishment of a chain of sale must be accompanied by a fish processing and other ways of preservation and transport. In this context, the concepts of intensive and extensive take a particular significance. Thus, the fish industry, a long time regarded as a way of geographically concentrated production factors and to achieve economies of scale is generally comparable with the intensive concept and privatization seems that he could not pass through it. It now appears that all such projects implemented so far on the African continent, have failed from their original purpose, ie to produce a fish at a lower cost price sale. It will thus be a question of establishing a system of production and of marketing of the production, which requires as first, a good feasibility study. This is excluded in zones where the demand for animal proteins must be rather fast because of a lack for the populations. On the other hand, this type of system can be developed after a first intervention of the production type.

II. SOME HISTORY… Although it was shown that the tilapia Oreochromis niloticus was rise in ponds by the Egyptians, there are nearly 4 000 years, the fact remains that the African continent, unlike Asia, has no tradition in fishfarming. At the beginning of the century, aquaculture was still totally unknown on the continent. The initial studies on tilapia date from the nineteenth century and the first attempts to develop aquaculture dates back to the 1940s. The attempts to introduce aquaculture in Africa around 1950, were for diversification of sources of animal protein to promote food self-sufficiency of rural populations. The first tests performed with tilapia in the station Kipopo established in 1949 (former Belgian Congo) have yielded promising results, the colonial government began outreach. In 1957 the station of Kokondekro near Bouaké in Côte d’Ivoire was created for the purpose of research and training. The first tests were carried on species now abandoned because of poor performance in intensive: Tilapia zillii, Tilapia rendalli and Oreochromis macrochir. It was not until the 1970s that it was found that the zootechnical performance of Oreochromis niloticus (formerly Tilapia nilotica) significantly exceeded those of most other tilapia. It is also from this period that one began to focus on the identification of other species of fish in Africa with high potential for aquaculture. But despite a massive help to promote family farming, like Asia, the results were disappointing.

III. A FISHFARMING OF SUBSISTENCE: GOAL AND PRINCIPLE In the framework of humanitarian NGOs, it is above all to enable people to have animal protein at a lower cost and within a short time. So a fishfarm in extensive to semi-intensive, of production, requiring minimal technical to be

Subsistence fishfarming in Africa

17

easily reproducible will be preferable. This, while producing in a rather short time a quantity of fish of consumable size. In many countries, fish from 80 to 100 g are consumed. It will thus not be a question of producing fish of 300 g or more, which takes a more important time. It is a fishfarming of self-consumption but artisanal. Important points: 99 Minimum of technique for a good appropriation by the beneficiaries, 99 Reduced impact on the environmental context: local species, 99 Fast production with lower costs, 99 Minimum of intervention on the ponds by the beneficiaries who have other major activities, 99 Minimum of inputs: alive or material. 99 Potentialities of Incomes Generating Activities (IGA): according to the size of the fishfarming and the number of ponds, one can arrive at a system allowing a IGA with use of people for the current maintenance and care on the ponds, while keeping an extensive system of production, because of technicality requested. The extensive fishfarming suggests a minimal action of man, with a prevalent contribution of the natural environment which one will seek to develop as well as possible. This practice is common in rural areas of the poor countries, where the level of average richness of the small producers does not allow them to acquire external inputs to the system. The meaning of the “extensive” character of the aquiculture is perceived paradoxically only compared to its degree of intensification, i.e. on the level growing of the intervention of the producer in the life cycle of the water orgaisms (Table IV, p. 16). It results from this an increase in investments and production costs while evolving of extensive to the intensive (Figure 6, p. 19). Collection of animal material (larvae, juveniles or subadults) into the wild, and its farming in captivity until a marketable size by using the techniques of farming constitutes the fishfarming based on fishery. These kinds of semi-fishfarm practices include the fishfarming on low level of inputs, practiced by the majority of the small fishfarmers of sub-Saharan Africa. It is based on the valorization of space by the fishfarm installation of the shallows in forest zone. The social aspects take more importance here, especially in the community management of the amplified fisheries. The fishfarming, in this case, makes it possible to bring a protein complement “fish”, that cannot only be provide by fishery. The association of the two systems, when they are present, also reduced pressure on the fishing resources. In terms of land needs, for a level of given production, the ponds require more land surface (or surfaces of water) that more intensive systems which, them, require high renewal rates of water. The fish ponds in general have a weak negative impact on the environment, except in the case of use of exotic species whose escape in natural environment can appear catastrophic. The ponds can be used to recycle various types of waste like the effluents (domestic or of livestocks), in environments directly or indirectly via stocked watershed stabilization and maturation (pond) where fish is the ultimate link. It is thus this approach which will be privileged within the framework of this handbook.

IV. POLYCULTURE VS MONOCULTURE Monoculture is the principle of using only one species in production in the fishfarm structures. The logic of polyculture is similar to the logic of crops. The association of fish with different diets increase the net yield and value of production. Polyculture allow an intensification of production per unit area, for against, it often leads to a decrease in the value of work. The principle used in a subsistence pond is to recreate a semi-natural ecosystem turning on itself. This is an intermediate situation between monoculture, where the flow of energy is concentrated on one species and a natural balance in which the beneficiaries of the flow are very diverse in terms of species. The target species are generally species at the bottom of the trophic chain, with a tendency to reproduce at small sizes. It is therefore to put other species, as predators, to control the population and ensure that fish are investing more in growth than in reproduction. In Africa, fish farms combine tilapia (often of the Nile, Oreochromis niloticus) as a main species with a Siluriformes (Heterobranchus isopterus, Clarias spp.), a Arapaimidae (Heterotis niloticus) and the predator Hemichromis fasciatus (to remove the unwanted fry) . In these conditions the secondary

18

Subsistence fishfarming in Africa

Investment Super-intensive

Deep-sea fishery

Intensive

Coastal fishery

Semi-intensive

Extensive

Aquaculture

Artisanal fishery

Pond, wetland

Fishery

Figure 6. Continuum Aquaculture - Fishery en relation with the investment intensification. (Mikolasec, 2008, under press) species may increase the total fish yield of over 40%. Whatever the species of tilapia used, with the increase in the number of age classes in an farm enclosure, competition leads rapidly to prevent a good growth of first stocked fish. The association of a predator to the farming of tilapia to control the undesirable reproduction of it is carried out today by a growing number of African fishfarmers. Within this framework, Siluriformes (Clarias or Heterobranchus sp.) are often regarded as having a double function: predation and polyculture. Associated results of farming Clarias - Tilapia show that a big number of individuals of Clarias is necessary to the total control of the reproduction of O. niloticus and that they exert a competition with respect to the food resources available in the pond. To control a population of 1200 tilapia in pond of 10 ares, a population of 260 Clarias of initial mean weight higher than 150 g is necessary and the growth of the tilapia is lower than that of an identical farming in which Clarias is replaced by a strict predator (Hemichromis fasciatus). It was also noted that, in the presence of a predator, the tilapia tend to invest in the growth before reproducing, which could be related to the fact that they can then better ensure the defense of their youngs. There exist various advantages to polyculture: 99 The natural foods are used better, in a more complete way, since only one species, even with a broad food spectrum, never uses all the food resources of a pond. 99 Certain trophic dead ends are avoided. The fish do not consume all the organisms as certain small crustaceans which can develop in the ponds. It is a question of controlling the populations of this invader by introducing a species which either will reduce the food of the intruder, or to feed itself directly on the intruder. 99 The production of natural foods is stimulated. The fish with digger behavior when they are in the search of food can suspend particles and, thus, aerate the sediment, to oxidize the organic

Subsistence fishfarming in Africa

19

matter and to improve recycling of the nutritive elements which stimulate the production of natural foods. 99 There can be a double fertilization. The dejections of herbivorous fish are so much “rich” that they have a fertilizing impact which can be compared with that of an associated terrestrial farming. This effect is sometimes named “double fertilization” because a chemical fertilization is much more effective when these fish are present in the mixed-farming. For example, this double fertilization can increase the carp yield from 14 to 35% compared to a normal fertilization obtained in pond of monoculture. 99 Water quality is improved. In pond, the presence of tilapia makes it possible to improve oxygenation of water. The tilapia improve also oxygenation by consuming the organic matter of the bottom which, if not, would have been mineralized by the bacteria consuming oxygen. 99 The organisms are better controlled. . The control of molluscs is possible in ponds while using Heterotis niloticus, whereas the proliferations of small wild fish or shrimps can beings controlled by using carnivorous fish. There exist also disadvantages with the polyculture which occur especially when an imbalance appears following a competition between the species. Moreover, when the fish density is very high, the role of the natural productivity of the pond in the diet of fish decreases, since the natural trophic resources must be allocated among all the individuals. The profit obtained by the practice of the polyculture is relatively limited, whereas the work caused by the sorting of the various species at the time of harvest becomes a real constraint. Monoculture is thus the only method of farming used in the intensive systems where the contribution of natural foods is very limited. In pond, high densities of fish are not current, because the oxygenation and the accumulation of toxic substances (ammonium, nitrites…) quickly become a limiting factor.

ÖÖ We therefore choose a fishfarming system of production, semi-intensive, of selfconsumption to artisanal, using polyculture rather than monoculture that request external food input and a more important follow-up if we want an interesting production.

20

Subsistence fishfarming in Africa

Chapter 03

BIOGEOGRAPHY AND FISH SPECIES I. GEOGRAPHY The fish faunas were established and have evolved according to the history of aquatic systems they occupy. They are far from being homogeneous for the whole of Africa. The existence and survival of aquatic habitats depend on two main factors: their morphology, which can be modified on the long term by erosion or tectonic; hydrological balance which depends on precipitation, evaporation, and infiltration, and for which small changes can lead to short or medium term to the drying or to the expansion of the aquatic environment considered, according to the shape of the basin. Communications can then be created between different basins. At various time scales, some basins have been colonized from other basins, and those colonizations have sometimes been followed by selective extinctions resulting from climatic and / or geological events. Simultaneously, some species were able to evolve to other species, and these speciation phenomena explain often the presence of areas of endemism. The African continent can be separate in several great ichthyologic regions or ichthyoregions (Figure 7, p. 22). They were defined according to affinities between fish faunas. Each region includes several catchment areas of different size. For example, the soudano-nilotic region includes several large basins like the Nile, Niger, Senegal. The political divison of the countries does not correspond little or not to the ichthyoregions. A country either is included completely in only one ichtyoregion, or with overlap on several. One will find in Annex 04, the Table XLVI, p. 246 which indicates for each African country the ichthyoregions of which its area forms part and in the Table XLIV, p. 240 of geographical information for each African country. ÖÖ It will be necessary to check in which country the intervention must take place and see the corresponding ichthyoregion. Then one can refer in the Annex, on the various tables for the species which may probably be used in aquaculture, particularly tilapia.

II. THE SPECIES Among the 292 farmed species listed by the statistics of FAO (1995) and for which data are available, the first 22 species represent 80 % of the total production. Among these 22 species, practically all the species are filterers, herbivorous, or omnivorous. Only one species, the Atlantic salmon, is carnivorous and it is clearly about a minor species in terms of volume of production. The most important group is that of fresh water fish: 12,7 million tons, in comparison with 1,4 million tons for amphihalins fish and 0,6 million tons for marine fish. The fresh water fish are dominated by Cyprinidae (carps) and Cichlidae (tilapia). Cyprinidae present a certain number of comparative advantages: they can use food with proteins and fish meal contents limited; they can beings raised in polyculture, allowing an optimal valorization of the natural productivity of the ponds and water pools in which they are stored; they also correspond to growth markets in the Asian countries, because of the traditions and the relatively low prices. For Africa, the aquacultural production remains mainly on two groups of indigenous species: the tilapia (12 000 tons annual) and the catfishes (7 000 tons), and of the introduced species of which the carps (2 000 tons). Historically in fact the tilapia were the subject of the first work of aquacultural experimentation in Africa, mainly in DRC (ex-Zaire) and in Congo, in particular because of their easy reproduction in captivity. Thereafter, various species were tested in order to determine their fishfarming potentialities. Thus, at the beginning of the year 1970, in Central African Republic, the high potential of the catfish Clarias gariepinus on which important research tasks were undertaken, have been put forward. Then in the years 1980, other species of fishfarming interest were identified, in

Subsistence fishfarming in Africa

21

Mediterranean Sea

Red Sea

Indian Ocean

Atlantic Ocean

Figure 7. The ichthyoregions (limits in yellow-green) and the countries (limits in red) (Faunafri). particular in Ivory Coast, on the basis of their appreciation by the zootechnical consumers and their performances. The biological cycle of some of them is now completely controlled, which allowed the starter of their fishfarming production.

II.1. THE CICHLIDAE

In Africa, the species mainly used in fishfarming are fish of the family of Cichlidae, group of Tilapiines. They are commonly called tilapia and are mainly herbivorous / microphagous. They practice parental care. Called “water chickens”, tilapia have biological characteristics particularly interesting for fishfarming: 99 They have a good growth rate even with a food containing few proteins;I 99 They tolerate a broad range of environmental conditions (oxygenation, salinity of water…); 99 They reproduce easily in captivity and are not very sensitive to handling; 99 They are very resistant to the parasitic diseases and infections;

22

Subsistence fishfarming in Africa

99 They are appreciated by consumers. We know more than a hundred species of «tilapia» described. More than 20 species have been recorded in some countries (Annexe 04 p. 239). Some are endemic of lakes or very circumscribed zones. The maximum size observed is very variable and does not reach more than 5 cm until more than 60 cm Total Length (TL). The species of Tilapiines are separate in various genera whose the 3 principal ones are Oreochromis, Sarotherodon and Tilapia. This separation in genera is mainly related to the mode of reproduction of these species. Oreochromis are maternal mouthbreeders, i.e. the females keep the eggs and juveniles in their mouth to protect them. The fish of the genus Sarotherodon are also mouthbreeders, but biparental, the two parents can incubate. The fish of the genus Tilapia are substrate spawners. The maximum growth obtained is of 3 grams per day. Oreochromis niloticus was one of the first to being cultivated, and remains the most common species. But many other species were also used: O. aureus, O. macrochir, O. mossambicus, Tilapia rendalli, T. guineensis, Sarotherodon melanotheron. This last, frequent in the estuariens and lagunaires western African ecosystems, appears more particularly adapted to a brackish water farming. Many of these species are now widespread in the whole world, either that they were introduced into natural environments to improve fishing, or which they are used as a basis for the fishfarming production. Between 1984 and 1995, the contribution of the tilapia of fishfarming to the total production of tilapia passed from 38 % (198 000 t) to 57 % (659 000 t). Four species or groups of species dominated the production between 1984 and 1995, where they contributed for 99.5 % to the production of all Cichlidae. The Nile tilapia represented 72 % of the total production of tilapia; the annual growth rate of its production between 1984 and 1995 was of 19 %. In 1995, the principal producers of tilapia were China (315 000 t), Philippines (81 000 t), Indonesia (78 000 t) and Thailand (76 000 t)! Other Cichlidae were used in order to control the populations of tilapia in the ponds. They are predatory species of the kinds Serranochromis and Hemichromis.

II.2. THE SILURIFORMES OR CATFISHES

Siluriformes are, in fact, the catfishes. They are separate in several families. The interest in fishfarming of African species is recent. Some species of Siluriformes are very interesting for fishfarming because of their robustness and their rapid growth. Three species are currently well studied for domestication: Clarias gariepinus, Heterobranchus longifilis and Chrysichthys nigrodigitatus. For example, Heterobranchus longifilis is present in most of the river basins of intertropical Africa, and has biological characteristics which are particularly favorable to fishfarming: capacity to support hypoxic conditions because of air breathing apparatus, omnivorous diet, high fecundity and quasi-continuous reproduction, remarkable growth potential (10 g per day). The reproduction of these species in captivity is controlled, but the larval growing remains the most constraining phase of the farming. The fishfarming potential of other catfishes, such as Clarias isheriensis, Bathyclarias loweae, Heterobranchus isopterus or H. bidorsalis, also was the subject of an evaluation. Tests on Auchenoglanis occidentalis were carried out in Ivory Coast. Some species of Siluriformes are strictly piscivorous and were tested for the control of the populations of tilapia in the case of polyculture. In addition to Heterobranchus longifilis, Schilbeidae, like Schilbe mandibularis, S. mystus and S. intermedius and Bagridae, Bagrus docmak, B. bajad… can be used.

II.3. THE CYPRINIDAE

Despite the abundance and diversity of Cyprinidae in African inland waters, with more than 500 described species, no species has actually been domesticated so far. Yet some species exceed 50 cm TL like Labeobarbus capensis (99 cm TL), and Barbus altianalis (90 cm TL). There was some attempts to introduce Asian Cyprinidae as common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix), mottled carp (Hypophthalmichthys nobilis) and grass carp (Ctenopharyngodon idella). The common carp was first introduced to Madagascar and then scattered in a dozen other countries including Kenya, Cameroon, Malawi, Ivory Coast and Nigeria. Tests were made with Labeo victorianus (41 cm TL) and Labeo coubie (42 cm TL). However, these are often species of running water and this can be a problem on their farm in pond where water is almost stagnant.

Subsistence fishfarming in Africa

23

II.4. OTHER FAMILIES AND SPECIES

In Annexe a list of species produced commercially in fishfarming in Africa, by country listed by FAO is presented (Annexe 02 p. 193). Other species, produced or not, but used also, in tests, like Nile Perch (Lates niloticus, Latidae, 167 cm SL), the predator introduced into Lake Victoria, for production and the control of the populations of tilapia in pond. Other species were tested, but the results are old and not easily findable in the bibliography. The domestication of new African species is considered. It is for example Gymnarchus niloticus (in Nigeria, Gymnarchidae; 167 cm SL for 18.5 kg), Parachanna obscura (Channidae, 50 cm SL for a maximum weight of 1 kg), Distichodus niloticus (Citharinidae, 83 cm TL, for a weight of 6.2 kg), In polyculture, a species used regularly is the Arapaimidae, Heterotis niloticus (100 cm SL, for a weight of 10.2 kg), in Ghana, in Nigeria, in Gambia, in Guinea and in Congo. It is clear, however, that the people quickly focused on less than 10 species. However, the potentials of many others were not tested and, within sight of the damage caused by the introductions of species, it would be advisable to develop the farming of indigenous species. One of the interests of the step of identification of indigenous species aiming at determining those having a potential interesting for the fishfarming, is to highlight neglected and badly known species revealing a potential higher than that of a species sister or a very nearby genus previously used; the other is that to avoid the introduction of allochtones species. Such is the case for example of Chrysichthys nigrodigitatus compared to C. maurus or that of Heterobranchus longifilis compared to Clarias gariepinus. This is also for the aim of diversification ÖÖ We should think that «what is found elsewhere is not better than what we find at home.»

24

Subsistence fishfarming in Africa

Summary FISHFARMING: AIM AND ISSUES WHY?

Fisheries and aquaculture contribute to the food security primarily in three ways: ÖÖ To increase the food availabilities, ÖÖ To provide highly nutritive animal proteins and important trace elements, ÖÖ To offer employment and incomes which people use to buy of other food products.

PRESSURE ON THE RESOURCES

The continental aquatic ecosystems are particularly affected by the human activities by: 99 Modifications of the habitat, 99 Water pollution, 99 Fsheries impact, 99 Introductions.

INTERNATIONAL ASPECTS

The Convention on Biological Diversity (CBD), known informally as the Biodiversity Convention, is an international treaty that was adopted at the Earth Summit in Rio de Janeiro in June 1992. The Convention has three main goals: 1. Conservation of biological diversity (or biodiversity); 2. Sustainable use of its components; 3. Fair and equitable sharing of benefits arising from genetic resources. ÖÖ Above all, the Convention is legally compulsory, the member states are forced to implement its mesures. ÖÖ This means to respect these mesures in the projects on the field while avoiding up to have an effect on the environment that may affect biodiversity. If so, this could turn against the organism responsible for the project despite the intentions and the tacit agreement of local and regional authorities.

OBJECTIVE OF FISHFARMING ÖÖ The objective of the fishfarming is not to replace fisheries but to supplement its contributions in maintaining the current level of fish consumption, regarding the increase of world population. However, this goal must be pursued in respect of environmental, consumer health and bioethics.

TYPE OF FISHFARMING VARIOUS TYPES OF FISHFARMING

The types of fishfarming depend mainly on the investment, the quantity of fish produced per unit of area and on the destination of the products. They are generally characterized by their degree of intensification.

Subsistence fishfarming in Africa

25

A FISHFARMING OF SUBSISTENCE: GOAL AND PRINCIPLE

So a fishfarm in extensive to semi-intensive, of production, requiring minimal technical to be easily reproducible will be preferable. This, while producing in a rather short time a quantity of fish of consumable size. It is a fishfarming of self-consumption but artisanal. Important points: 99 Minimum of technique for a good appropriation by the beneficiaries, 99 Reduced impact on the environmental context: local species, 99 Fast production with lower costs, 99 Minimum of intervention on the ponds by the beneficiaries who have other major activities, 99 Minimum of inputs: alive or material. 99 Potentialities of Incomes Generating Activities (IGA): according to the size of the fishfarming and the number of ponds, one can arrive at a system allowing a IGA with use of people for the current maintenance and care on the ponds, while keeping an extensive system of production, because of technicality requested.

POLYCULTURE VS MONOCULTURE

Monoculture is the principle of using only one species in production in the fishfarm structures. Polyculture is the association of fish with different diets which increase the net yield and value of production. ÖÖ One therefore choose a fishfarming system of production, semi-intensive, of selfconsumption to artisanal, using polyculture rather than monoculture that request external food input and a more important follow-up if one want an interesting production.

BIOGEOGRAPHY AND FISH SPECIES GEOGRAPHY

The fish faunas were established and have evolved according to the history of aquatic systems they occupy. They are far from being homogeneous for the whole of Africa. The African continent can be separate in several great ichthyologic regions or ichthyoregions. They were defined according to affinities between fish faunas. ÖÖ It will be necessary to check in which country the intervention must take place and see the corresponding ichthyoregion.

THE SPECIES

Aquaculture production is based primarily on two groups of species: the Cichlidae with tilapia and Siluriformes or catfish. Individually, the species of tilapia and catfish are not necessarily distributed over the whole of Africa. But both groups are everywhere. ÖÖ It will thus be a question of paying attention to the source of fish to be used and the drainage basin where the action is undertaken, this, because of the risks incurred by the introduction of fish and the national and international legislative aspects concerning the biodiversity ÖÖ It is not either because a species was already introduced into the zone of intervention, that it should necessarily be used. ÖÖ We should think that «what is found elsewhere is not better than what we find at home.»

26

Subsistence fishfarming in Africa

Part II

PRACTICAL ASPECTS

Contents • The initial pre-project assessment

Implementation plan

• Villages selection • Sites selection • Characteristics of ponds • The construction of ponds • Biological approach • The handling of the fish • Maintenance and management of the ponds Subsistence fishfarming in Africa

27

CONTENTS - PART II Chapter 04 - THE INITIAL PRE-PROJECT ASSESSMENT

33

I. THE ECOSYSTEM

33

II. THE ASSESSMENT

36

III. PRINCIPLE

37

IV. BIOLOGICAL AND ECOLOGICAL ASSESSMENT

38

V. SOCIO-ETHNOLOGY

40

V.1. Socio-economic and cultural characteristics

40

V.2. The relations man-resources

40

V.3. The relations man-man

41

Chapter 05 - VILLAGES AND SITES SELECTIONS

43

I. THE VILLAGES SELECTION

43

II. THE SITES SELECTION

45

II.1. The water

45

II.2. The soil

50

II.3. The topography

53

II.4. The other parameters

56

Chapter 06 - CHARACTERISTICS OF THE PONDS

59

I. DESCRIPTION

59

II. TYPES OF PONDS

59

II.1. Barrage ponds

62

II.2. Diversion ponds

62

II.3. Comparison

62

III. CHARACTERISTICS III.1. General criteria

63

III.2. Pond shape

66

III.3. According the slope

67

Cover photo: Ö Ö Villagers working on the pond, Liberia, ASUR, 2006 - © Yves Fermon

28

63

Subsistence fishfarming in Africa

III.4. Layout of ponds

67

III.5. Size and depth of the ponds

68

III.6. Differences in levels

69

IV. SUMMARY

71

Chapter 07 - THE CONSTRUCTION OF POND

73

I.

73

THE DESIGN PLAN

II. THE CLEANING OF THE SITE

75

III. WATER SUPPLY: WATER INTAKE AND CHANNEL

77

IV. DRAINAGE: CHANNEL OF DRAINING AND DRAINAGE

81

V. THE PICKETING OF THE POND

82

VI. THE CONSTRUCTION OF THE DIKES

83

VII. THE DEVELOPMENT OF THE PLATE (BOTTOM)

89

VIII. THE CONSTRUCTION OF THE POND INLET AND OUTLET

90

VIII.1. Pond inlet structures

90

VIII.2. Pond outlet structures

94

VIII.3. Sedimentation tank IX. ADDITIONAL INSTALLATIONS

105 106

IX.1. The anti-erosive protection

106

IX.2. The anti-erosive fight

107

IX.3. Biological plastic

108

IX.4. The fence

108

IX.5. The filling of the pond and tests

109

X. NECESSARY RESOURCES

109

X.1. Materials

109

X.2. Human Resources and necessary time

110

XI. SUMMARY

112

Chapter 08 - BIOLOGICAL APPROACH

113

I. THE LIFE IN A POND

113

I.1. Primary producers

115

I.2. The invertebrates

116

I.3. The vertebrates

118

Subsistence fishfarming in Africa

29

II. THE FERTILIZATION

30

118

II.1. The fertilizers or manure

118

II.2. The compost

121

III. SUMMARY

126

Chapter 09 - THE HANDLING OF THE FISH

127

I. CATCH METHODS

127

I.1. Seine nets

129

I.2. Gill nets

132

I.3. Cast nets

133

I.4. Dip or hand nets

134

I.5. Traps

135

I.6. Handline and hooks

136

II. THE TRANSPORT OF LIVE FISH

136

III. THE PRODUCTION OF FINGERLINGS OF TILAPIA

139

III.1. The recognition of the sex

139

III.2. The nursery ponds

139

III.3. Hapas and cages

142

III.4. The other structures

145

IV. THE STOCKING OF THE PONDS

146

V. THE FOLLOW-UP OF FISH

149

VI. DRAINING AND HARVEST

150

VI.1. Intermediate fishings

150

VI.2. Complete draining

151

VII. SUMMARY

152

Chapter 10 - MAINTENANCE AND MANAGEMENT OF THE PONDS

153

I. THE MAINTENANCE OF THE PONDS

153

I.1. The diseases of fish

153

I.2. The feeding of the fish

158

I.3. Daily activities of follow-up

162

I.4. Maintenance work after draining

163

I.5. Fight against predators

164

Subsistence fishfarming in Africa

I.6. Summary

164

II. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION

165

III. THE MANAGEMENT OF PONDS

167

III.1. Fish Stocks and useful indices for monitoring

167

III.2. The expected yields

168

III.3. The management of harvests

168

III.4. Several kinds of production costs

170

III.5. Record keeping and accounting

170

III.6. The formation

171

IV. PONDS AND HEALTH

171

On the next page, the reader may find the overall implementation plan for the establishment of ponds. The chapters follow the plan. As the progress of the manual, it will be mentioned at the beginning of each chapter showing step processed.

Subsistence fishfarming in Africa

31

0

3 months

Assessment Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Duration: 3 months

Selection Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Draining channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas

Completion and filling in water

Duration: 6 - 9 months 3 to 6 months

Fish farming Fertilization

Outside composter

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Stocking with tilapia Follow-up  of the fishes

7 - 10 months

Stocking with  predators

Duration: 4 to 12 months

End of the cycle 11 - 22 months

Storage of  fishes

Draining of the pond  and harvest Sale and\or transformation  of the fish

Duration: 0.5 to 1 month

Figure 8. General implementation plan.

32

Maintenance and  follow-up of the  ponds

Subsistence fishfarming in Africa

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

Chapter 04

THE INITIAL PRE-PROJECT ASSESSMENT Initially, the phases of evaluation intervene o determine the utility and the relevance for the populations of the implementation of any project. This would take into account: 99 Requests of populations, 99 Available resources and environment. As a first step, we will describe the environment and ecosystems. Then we discuss the various aspects of evaluation. This step has a duration of at least 3 months, which may increase depending on the importance of the program and the geographical area to assess (Figure 9, p. 34).

I. THE ECOSYSTEM An ecosystem is a dynamic complex composed of plants, animals and micro-organisms and inert nature, which is subject to complex interactions as a functional entity. Ecosystems vary greatly in size, lifetime and operating. A temporary pond in a hole of a tree and an ocean basin are both examples of ecosystems. The communities of plants, animals and micro-organisms form a biocoenosis. This one is characterized by a food chain (or trophic), from the primary producer (the plant build the organic matter starting from light energy, CO2 of the air and the mineral ions of the ground), to the various consumers (from the herbivorous to the super predator), while passing through the various decomposers in charge of ensuring the return of organic matter in mineral form in the soil. Inert nature is also known as the biotope. It includes all geographical and physicochemical ecosystem characters (climate, soil, topography, water…) To analyze and describe a given ecosystem, one uses the concept of factor ecological. Is known as ecological factor, any element of the external environment which may affect the development of the living beings. For this reason, one distinguishes several types of ecological factors: 99 Biotic factors, related to the biological components (biocénose), interactions of alive on alive, intraspecific (within the same species) and interspecific one (between two different species or more); 99 Abiotic factors, related to the physicochemical conditions of the environment (biotope). An ecological factor acts as a limiting factor when it determines the potential success of an organism in its attempts to colonize an environment. This factor can be limiting as well by its absence as by its excess. With respect to the ecological factors, each living being thus presents tolerances limits between which is located the zone of tolerance and the ecological optimum. Thus the ecological valence of a species represents its capacity to support the more or less large variations of an ecological factor. The ecological factors can thus act in various ways on the biocénose. They in particular will intervene on: 99 The biogeographic distribution area of the species; 99 The density of the populations;; 99 The occurrence of adaptive modifications (behavior, metabolism). Thus when the presence of such or such species informs us about the characteristics of its environment, this one is called biological indicator. The particular characteristics (a biotope implying such type of biocoenosis and conversely) of each ecosystem allow a zoning. Consequently for each type of ecosystem, it is possible to associate with this zoning: an operating process, goods and services produced, known risks and threats… The human beings, as an integral part of the ecosystems, draw benefit from the “goods and services” produces by the functioning of the ecosystems. The services provided by the ecosystems include the services of deduction such as food and water; services of regulation like the regulation

Subsistence fishfarming in Africa

33

0

3 months

Assessment Duration: 3 months

Selection

Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Drainig channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas Duration: 6 - 9 months 3 to 6 months

Completion and filling in water

Fish farming Fertilization

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Maintenance and  follow-up of the  ponds

Stocking with tilapia Follow-up  of the fishes

7 - 10 months Duration: 4 to 12 months

Stocking with  predators

End of the cycle 11 - 22 months

Outside composter

Storage of  fishes Duration: 0.5 to 1 month

Draining of the pond  and harvest Sale and\or transformation  of the fish

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Figure 9. Setting of fish ponds: 1. Assessment.

34

Subsistence fishfarming in Africa

Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

1. ASSESSMENT of the floods, the dryness, the disease and impoverishment of the soil; services of self-maintenance like the formation of the grounds, the development of the nutritional cycle; finally culture sections like the benefit of approval, the esthetic benefit and the other nonmaterial advantages. These various “services” result from the functioning of the ecosystems, i.e. of the whole of the biogeochemical reactions affecting the biosphere and being characterized by permanent exchanges of matter and energy along the various cycles (water, carbon, nitrogenize…) and food chains. Because of the various cycles (like that of water, Figure 10 below), all the ecosystems are strongly open the ones to the others. There exist however more or less porous borders called ecotones. The edge of a wood separating it from an agricultural field, a hedge cuts wind are good examples. Like any border, these zones are important places of transit and exchange. One of the most known ecotones is the wetland, zone of transition between the terrestrial and water environments. The wetlands constitute a vast inter-connected network of exchange including the lakes, rivers, swamps and the coastal regions. The living conditions and production of a human community depend always directly or indirectly on the abundant services by the local ecosystems (water, food, wood, fiber, genetic material…). As example, the exploratory studies undertaken within the framework of “Millenium Ecosystem Assessment” teach us that the demand for food (thus in service of deduction, of self-maintenance…) could grow from 70 to 80 % over the 50 next years. With which ecosystems? This increasing demand will generate necessarily larger difficulties for the communities on the level of the access to the resources and will increase for all, the cost of the security of the provisioning, from where the concept of territorial vulnerability. Because of interconnection of all the ecosystems, heterogeneous scales of time cross on the same territory: global environment (climate, biogeochemical major cycle) which evolves over a long period, local environment (production of biomass) over the medium period, human communities over the short period. What to say on climate change, true producing of uncertainties affecting the global environment. These moving temporalities and borders within the territories reinforce the prospective need for the analyzes.

Evapotranspiration

Precipitation Evaporation

Surface runoff

Stream flow Source Infiltration Sea Ground water flow

Figure 10. Water cycle.

Subsistence fishfarming in Africa

35

To take account of these dependences and inter-connected multiple, of variable contamination temporalities and distances, the ecosystemic approach of the territories appears most relevant. Thus let us retain that there exist direct and indirect relationships between vulnerability of the environment, within the meaning of the whole of the ecosystems present on a territory, and vulnerability of the human communities which there are included and fully live, in a territory, on goods and services gotten by its ecosystems. ÖÖ It will thus be a question of carrying out the evaluation of the ecosystem in all its components, human beings included, in order to see which are the actions to propose to ensure a better “wellbeing”, mainly of food safety but also of health and water and sanitation.

II. THE ASSESSMENT It will thus be a question of evaluating: The 3 points according the Figure 11 below: 1. The men. 2. The ressources. 3. The human actions on the ressources.

According the 2 major issues: (i) Biology and ecology: points 2 and 3. (ii) Socio-ethnology: points 1 and 3

The ideal would be to be able to carry out these two topics of evaluation jointly. In the case of the interventions in post-urgency, one of the factors limiting is time. It will thus be necessary to center mainly the intervention in the shortest possible time and to carry out a “fast evaluation”.

FIELD - ECOSYSTEM

2 3

RESOURCES

1

VILLAGE

Figure 11. Contextual components of the assessment. 1: The men; 2: The ressources; 3: The human actions on the ressources.

36

Subsistence fishfarming in Africa

1. ASSESSMENT III. PRINCIPLE The fast evaluation can be defined like: “A synoptic evaluation often undertaken in urgency, within the shortest possible time possible, in order to produce results reliable and applicable to the definite goal”. Whatever the fast evaluation that one prepares, it is necessary to take into account of the nine following points: 1.2The fast type of evaluation. The fast evaluation can go from a theoretical study to a field study, through meetings of groups of expert and workshops. It can include/understand compilation of existing knowledge and specialized data, including traditional knowledge and data, and methods of study in the field. 2.2The evaluations can be done in three stages: design/preparation, application and establishment of the reports. The fast evaluations provide the necessary results within the practical shortest times, even if the preparatory period and the work of planning which precede the study are consumers of time. In some circumstances (when one takes account of seasonal factors, for example) it can run out of time between the decision to undertake the evaluation and its realization. In other cases (in the event of disturbance and of catastrophe, for example), the evaluation will be undertaken in urgency and the preparation time must remain minimal. 3.2Inventory, evaluation and follow-up. When one conceives exercises of data acquisition the type of necessary information is different in each case and it is important to distinguish the inventory, the evaluation and the follow-up. The inventory of reference of the wetlands is used as a basis for the development of a suitable evaluation and a follow-up. The inventories of the wetlands, repeated with certain intervals, do not constitute necessarily a “follow-up”. 4.2The cost increases, in particular, during the evaluation of isolated zones, in the case of vast space scales, of a topographic high-resolution and/or a great number of the types of characteristics. The cost of an evaluation undertaken quickly will be higher, for example, because it is necessary to have large teams in the field simultaneously and to support them. 5.2Space scale. The fast evaluations can be undertaken on various space scales. In general, a fast evaluation with large scales consists in applying a standardized method to a great number of localities or stations of sampling. It is clear that the more the zone is extended, the more time requested can be long, depend on the number of implied people, and thus the higher cost. 6.2Compilation of the existing data/access to the data. Before deciding to carry out a new evaluation on the field, the first big step consists to compile and evaluate the highest possible number of data and information existing and available. This part of the evaluation should determine the data and the information which exist like their accessibility. The data sources can include the geographical information systems (GIS) and the teledetection, the data published and not published and traditional knowledge and data obtained by the contribution of local populations and indigenous. This compilation must be used as lack analysis making it possible to determine if the goal of the evaluation can be reached with existing information or if it is necessary to lead a new study in th field. A good cartography is essential to the good way of the evaluation and the future decisions concerning the projects to be proposed. 7.2For all new data and information collected during a later fast evaluation in the field, it is essential to create a traceability of the data. 8.2Reliability of the data of fast evaluation. In all the cases of fast evaluation, it is particularly important that all the results and products contain information on the confidence limits of the conclusions. If possible, it is advisable to evaluate the propagation of error by the data and information analysis to provide a comprehensive assessment of the confidence limits of the final results of the evaluation. 9.2Diffusion of the results. An important element of any fast evaluation is the fast, clear and open diffusion of the results near a range of actors, decision makers and local communities. It is essential to present this information to each group in the form and with the level of precision which is the best appropriate. Subsistence fishfarming in Africa

37

In this case, two aspects are to be treated and, preferably, jointly, in relation to the wetlands and its resources: ÖÖ The biological aspect and resources;

ÖÖ The socio-ethnological aspect and the man. ÖÖ Preferably, two specialists will be necessary with priority for the biological aspects.

IV. BIOLOGICAL AND ECOLOGICAL ASSESSMENT The methods available for a fast evaluation of the biodiversity of the wetlands are dependant on the goal and the results of specific projects. The factor of the available resources and the limitations is quite as important, in particular because it influences the range of the evaluation. Time, the money and the expertise are limitations of resources which determine the methods available for a particular project of evaluation. Moreover, they define the project from the point of view of its range in the following fields: systematics, geography, choice of the site, analyzes, data and sampling procedures. They are important components of an evaluation of the biodiversity of a wetland and the range or the capacity of each one varies according to the needs for the project and its limits in resources. One of the points important is to establish the statement of the area. ÖÖ The hydrographic network of a country is its “blood system”. Any damage in a point will be found downstream from this point, wether it is chemical, urban, related to erosion… Water, it is the life. Current and well-known sentence but in the health, water and sanitary and food security (agriculture, fish), it is the main common factor. As for the human body where one looks at the blood system to establish a diagnosis, one can study the rivers to evaluate the health of an area and to thus know the points where it is necessary to intervene.

One of the best indicators to evaluate water quality is its biological components e.g invertebrate (crustaceans, molluscs, insects…), vertebrate (fish). An evaluation of the indicators supposes that biological diversity, from the point of view of the diversity of the species and the communities, can give informations on water quality, the hydrology and the health in general of particular ecosystems. The “biomonitoring” is a monitoring often associated with this type of evaluation. Traditionally, that relates to the use of biological indicators to follow-up of the levels of toxicity and the chemical contents, but recently, this type of approach was more largely applied to the follow-up of the total health of a system rather than of its physical and chemical parameters only. The presence or the absence of some chemical or biological indicators can reflect the environmental conditions. The taxonomic groups, the individual species, the groups of species or the whole communities can be used as indicators. Usually, the benthic macro-invertebrates, the fish and the algae are used as organic indicators. It is thus possible to use the presence or the absence of species, and in certain cases the abundance and the characteristics of the habitat, to evaluate the state of ecosystems of wetlands. The use of biological criteria to follow the quality of the courses of the rivers in temperate countries is common. It is less the case for the tropical countries. The biological index of integrity (IBI) has been used for more than 10 years in Europe and North America. It allows an estimate of the health of a river by the analysis of its fish settlement. The maintenance of water quality is a major concern for human society which must provide for increasingly important requirements of water, and this, as well from the quantitative point of view as qualitative. The evaluation of the resources has the aim of determining the durable potential of use of the living resources in a given zone or a given aquaic system. The data deal with the presence, the state

38

Subsistence fishfarming in Africa

1. ASSESSMENT and the conditions of economic species, of species on which depend the means of existence and of species which have a potential commercial value. In good logic, it would be good that an evaluation of the resources facilitates the ecologically durable development rather than or not durable destroying activities. The importance of the choice of fish as indicator is its importance also as an animal protein contribution. It is a question of surveying which are the resources available in the rivers close to the targeted villages. It is supposed that any fast evaluation must be done with the end objectives of conservation and rational use. The methods used are supposed to increase knowledge and understanding for the purpose of establishing a reference, the evaluation of the changes in the ecosystems or their state and the support to the durable use of the resource. In this context, there are five precise reasons to undertake a fast evaluation of the wetlands which cover the extent of the possible reasons: 1. To collect general data on the biodiversity in order to inventory and to treat on a hierarchical basis the species, the communities and the ecosystems of the wetlands. To obtain reference information on the biodiversity for a given zone. 2. To gather information on the status of a target species (such as a threatened species). To gather relative data with the conservation of particular species. 3. To obtain information on the effects of the natural or induced disturbances (changes) by the man on a zone or a particular species. 4. To obtain indicating information of the general health of an ecosystem or of the statement of a particular ecosystem of wetland. 5. To determine the possibility of using in a durable way the living resources in an ecosystem of a particular wetland. Many fast evaluations do not allow to entirely evaluate the threats or the pressures on biological diversity. Nevertheless, it can be useful, in order to determine it on what should carry a future evaluation, to make a provisional evaluation of the categories of threats. It is important to note that the methods of fast evaluation of the wetlands are generally not made to take into account the variations in time, like the seasonal character, in the ecosystems. However, some methods of fast evaluation can be (and are) used in iterative studies as elements of a program of integrated follow-up, in order to take account of this variation in time. The techniques of fast evaluation are appropriate particularly at the specific level of biological diversity and the present orientations are interested in the evaluations on this level. The evaluations on the genetic level of biological diversity generally are not related to “fast” approaches. Nature complexes and the variability of the ecosystems of the wetlands make that there does not exist universal evaluation fast method, applicable to all the range of the types of wetlands and to the diversity of the goals for which the evaluations are undertaken. Moreover, which it is possible to make, in a particular case, depends on the resources and the capacities available. In a general way, the goal is to gather as much information than possible on an ecosystem of wetland by sampling wide and as complete as possible of the biological elements and associated characteristics. The lists of species and habitats will be probably the most important form of data, but of other relevant data could include: species richness, abundance, relative size of the populations, distribution and the surface of distribution, cultural importance in addition to the importance for the biodiversity and other relevant biological information which is due to water quality, the hydrology and the health of the ecosystem. The data on the geography, geology, the climate and the habitat are also important. For the majority of the studies, it would be good to measure a diversity of variables of water quality. Those can include the temperature, electric conductivity (EC, a measurement of dissolved total salts), the pH (measurement of the acidity or alkalinity of water), chlorophyl A, total phosphorus, total nitrogen, oxygen dissolves and the transparency of water (with the disc of Secchi). These variables can be measured with individual instruments or a combination of instruments including several types of probes. One can seek the macrophytes visually. The fish can be sampled with a great diversity of methods, while taking into account the applicable legislation. To work with the local fishermen and to examine their catches can be also an invaluable source of information. In order to ensure this part properly it is essential that a specialist can intervene. A generalist will be limited by his knowledge concerning the aquatic organisms and the functioning of the ecosystems.

Subsistence fishfarming in Africa

39

The data essential and minimal to collect are: ÖÖ The number of species, ÖÖ Quantity of individuals by species for a given time of sampling, ÖÖ The presence/absence of pilot species, ÖÖ The physicochemical quality of water (rate of nitrates/phosphates, pH, Oxygen, conductivity, turbidity). In the collected species, one will be able to thus see which are available for fishfarming. The local communities can be an important source of information on the richness of the species in a given habitat. One can, for example, by studies of the communities and consumption, to gather information in very short time. From where, the importance of a joint analysis with an socio-ethnological approach.

V. SOCIO-ETHNOLOGY V.1. SOCIO-ECONOMIC AND CULTURAL CHARACTERISTICS It is also important to gather information on the socio-economic and cultural characteristics of biological diversity although a complete economic evaluation is, generally, out of reach in fast evaluation. Nevertheless, within the framework of a fast evaluation of inventory or an evaluation of the risks, it can be useful to obtain a first indication of the socio-economic and cultural characteristics which have an importance for the study of the site. That provides an indication of the probable changes in the base of natural resources and can be used to determine the characteristics which should be the subject of a more detailed evaluation of follow-up. It is advisable to take into account in particular: 1. Paleontological and archaeological registers; 2. Historical buildings and artefacts; 3. Cultural landscapes; 4. Traditional systems of production and agro-ecosystems, for example exploited rice plantations, saltworks, estuaries; 5. Practices of collective management of water and lands; 6. Practices of self-management, including the usual property rights; 7. Traditional techniques of exploitation of the resources of the wetlands; 8. Oral tradition; 9. Traditional knowledge; 10. Religious aspects, beliefs and mythology; 11. “Arts” - music, song, dance, painting, literature and cinema. In addition to the traditional evaluation of the nutritional and medical state of the local population, It is advisable to raise several questions when one arrives in an inhabited area.

V.2. THE RELATIONS MAN-RESOURCES

¾¾ Do there exist taboos? beliefs? It will be a question of evaluating the relations man/fish/river (belief). Food taboos exist, to differing degree, in all the cultures. It is obvious that food, basic element with the subsistence of the man (like other living beings), is a field where distinction between allowed and forbidden, the pure one and the impure one, is fundamental, for medical reasons, morals or symbolic systems. The taboos can have several justifications: nuns, medical, morals, psychological and emotional. These various justifications may be mixed. There other habits relate to fish and assign still the women and the children. It may be that it is about a true taboo, although often people who are not accustomed to eat fish do not like it for the simple reason that “smell bad” or “resembles a snake”. In some communities, the range of the taboos for the pregnant mothers was formerly so

40

Subsistence fishfarming in Africa

1. ASSESSMENT wide that it was almost impossible for them to have a balance diet. For example, part of the Bahaya people which live close to Lake Victoria was accustomed to prohibiting the egg and milk, fish, meat consumption to the pregnant women. Do there exist fish known as “patrimonial” i.e. having an importance to the level of the symbolic system? In other cases, there is the prohibited fishing in some areas throughout a village. Some of these prohibitions were put in place just to avoid an excessive level of predation in an area rich in fish and thus the management of fish resources. ¾¾ How is fishing perceived? In a certain number of ethnos groups, the practice of fishing is regarded as an activity for the lower castes. To be fishing and live fishing then are very discredited. ¾¾ Which are the resources used? By looking at the women preparing the meals and what they prepare, while carrying out of the visits at the market, one will be able to realize on behalf of fish in the food day laborer. In Ethiopia, for example, the fish is consumed mainly at the time of the Lent. If the fish is present in the food, it will then be a question of making sure of its source and its availability. For example, in Liberia, the villages near the rivers did not have any problem of supply fish in spite of an interest for fishfarm, whereas 10 km further, another village had supply problems. ¾¾ Which are the produced resources? A visit of the fields and a census of the cattle and animals present make it possible to realize of the diversity of the food products available. It will be necessary, however, to separate well the cattle which would be of “prestige” with the animals used for the human consumption. ¾¾ What are the water supplies? An important aspect is the supply of water for people. It will therefore seek the water points where people will be provided (well, pump, river…) and assess their condition.

V.3. THE RELATIONS MAN-MAN ¾¾ Who does what? Which is the role of the women and of the men? Uses and tasks. There is a division of labor between the men and the women. Among fishing people, most of the time, they are the men who go to fishing but the women deal with collecting fish, to transform it and sell it. At others, fishing is practiced by the women and becomes a corporate measure. In Liberia, the women with the children go away the afternoon to the river to capture with large scoops nets. They take the opportunity to exchange the latest news from the village. ¾¾ Which is the social structure? The way in which the village is structured is particularly important to know on which scale and which are the key and notable people. The groupings, their operation…, are a key of the success of programs in the field. ¾¾ Which is the system of division of the lands? The type of division of the lands, their membership, the land rights are as many variables which are important to know insofar as fishfarms will be established on some privileged zones. Water and its management are also an important parameter. Most of the time, this information can be collected in the form of investigations for which humanitarian NGOs like ACF have good experience in the past. It is, however, important not to be satisfied to discuss with the villagers, as that is sometimes the case. In some cases, one will have to deal with communities which have already experience of fishfarming, often with failures. The system especially developed in countries having an old fishfarming tradition and where ancestral know-how, although empirical, plays a crucial role. The many attempts at transfer of these fishfarming models towards countries where there was no fishfarming tradition failed.

Subsistence fishfarming in Africa

41

Many explanations were put forward to analyze the difficulties encountered in the development of fishfarming in Africa: ÖÖ Of social order, rural populations not having traditions and thus knowledge in this field;

ÖÖ Of technical order, on recent time, the techniques of fishfarming were not controlled yet perfectly, which had as a consequence a poor production in quality and quantity; ÖÖ Of economic order, the fishfarming developed in the context of an activity of subsistence in family matter, generally without profitability. We must therefore ascertain the presence of former ponds for fish production. If so, the challenge will be to unlearn first to allow relearning.

ÖÖ The whole of collected information will allow: ÖÖ To know the statement of the zone where the intervention must take place; ÖÖ To know the available resources usable and their current use; ÖÖ To know the communities and social structures. ÖÖ The goal being to have the elements to propose a solution allowing a good appropriation of the project by the populations, if the various components make it possible to affirm that fishfarming is a solution for the zone considered.

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Subsistence fishfarming in Africa

Chapter 05

VILLAGES AND SITES SELECTIONS If the initial assessmenst justify an intervention, the first stage will be thus to choose villages of establishment, by making sure that those have adequate sites in the vicinity (Figure 12, p. 44). This choice can be already more or less defined according to the preliminary assessment and of the visits of field which took place during this evaluation.

I. THE VILLAGES SELECTION As in all the actions undertaken under development and post-urgency, the choice of the villages and communities, then that of the beneficiaries is particularly delicate. In the majority of the cases, the target goes on the populations considered as most vulnerable. Various points will decide the approach of villages: 99 The first aspect inherent in the way of operating of ONG will be the presence of populations said vulnerable. 99 Proposed projects are usually fairly short. The number of villages targeted should therefore be chosen depending on the duration and logistics that will be available. However, it is unrealistic to propose a fishfarming project for less than 12 months. Indeed, the establishment of a pond of 200 m2 overall request 20 days to 20 people. If it is the beneficiaries who lead the workforce, it must take into account the fact that for most, their main activity is agriculture and they thus will devote only a time restricted to the construction of the pond. 99 One will not be able to also choose villages too distant because of times from transport and inherent logistics. Often, the technicians are used as catalysts for the beneficiaries and their presence is essential for the motivation and the follow-up. In the same way, the roads are often damaged and not very practicable. For that, a good cartography is essential and can be implemented during the evaluation. 99 No sources of fish in quantity near. Indeed, the presence of close sources of fish in considerable quantity will be a brake for the development of fish ponds. Unfortunately, many times, there will be the certainty which the villagers are motivated whereas in fact, their interest is located especially to obtain something on behalf of international NGOs operating in the zone. It will often be a total fiasco as the village investment in building ponds. It will thus be a question of seeing well whether the proteins fish are essential and missing in the zone. This means to see if the fish proteins are essential and missing in the area. This will be particularly important if the request comes from the villagers, this will bring more weight to their request. 99 Presence of sources or rivers near the village It is one of the crucial points of the choice of the villages and which will be taken again more in detail in the following paragraph (paragraphe II, p. 45). It is essential that the village has enough running water nearby. 99 The motivation of the villagers. It is one of the delicate aspects. It is very difficult to judge at first the general motivation. Generally, this vision of the motivation will come with the beginning of the work. However, the ethnographic preliminary study will provide information on the first aspects of this motivation but also of the elements allowing a good appropriation of the project by the beneficiaries. It is necessary that the beneficiaries understand that constructions carried out will belong to them and that this work will not belong at all to the NGO which supports the project, as it will not be used to establish this type of project if the villagers don’t want it. It is not, certainly, question of imposing anything… If possible, he is advisable to choose family groups people, which will avoids interfamilies problems for the management and distribution of harvests. If perennial associations would exist, it

Subsistence fishfarming in Africa

43

0

3 months

Assessment Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Duration: 3 months

Selection Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Drainig channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas Duration: 6 - 9 months 3 to 6 months

Completion and filling in water

Fish farming Fertilization

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Maintenance and  follow-up of the  ponds

Stocking with tilapia Follow-up  of the fishes

7 - 10 months Duration: 4 to 12 months

Stocking with  predators

End of the cycle 11 - 22 months

Outside composter

Storage of  fishes Duration: 0.5 to 1 month

Draining of the pond  and harvest Sale and\or transformation  of the fish

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Figure 12. Setting of fish pond: 2. Selections.

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Subsistence fishfarming in Africa

Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

2. SELECTIONS will be also possible to work with them according to their motivation and of their social cohesion. Once this choice will be carried out, it will be a question of passing to the second phase, i.e. the presence of favorable sites in the selected village. ÖÖ The choice of the village must take into account: ÖÖ Vulnerability of the population, ÖÖ Logistics, ÖÖ Water resources, ÖÖ Motivation of the villagers.

II. THE SITES SELECTION ÖÖ This is the most important step for a fish pond. The design and the realization of the ponds must allow the most perfect possible control of water. Moreover, the quality of the fishfarming works determines also the facility with which the followup, harvest and the sorting can be done. In other words, they determine the feasibility of a fishfarm. It is advisable to evaluate each potential site by a series of fast feasibility studies to check that the principal requirements are respected. In this chapter and the following, the major part of the drawings and texts are classic and often comes from various booklets, mainly those of FAO.

II.1. THE WATER

II.1.1. AVAILABILITY OF WATER

It will be necessary to take into account of the temporal variations of the inland waters, in particular the variations in the modes of flow of various types of inland water ecosystems which can include: 99 Perennial systems which know flows of surface all the year and are not drained during the drynesses. 99 Seasonal systems which know expected flows during the annual rainy season, but which can be dry during several months of the year. 99 Episodical systems (periodic or intermittent) which knows flows during one prolonged period, but which are neither predictable, nor seasonal. These systems are generally supply as well by rainwater as by subterranean water. Sometimes, flows of surface can only occur in some parts and become underground in the others. 99 Transitory systems (with short life) which know briefly and seldom flows and which, between two, return under dry conditions. Their flow generally comes from precipitations. A running water present continuously throughout the year (dry and rainy season) facilitates the management of ponds. One thus will seek the perennial systems. This allows for a possible renewal of the water of the pond, however slight, and thus have a good oxygenation and mitigating water loss. The amount of water needed will depend on the size of ponds, soil and climate prevailing in the locality.

■■ WATER FOR THE BASINS

It is easy to calculate the quantity of water of a basin. It is a simple calculation of volume: volume = lenght x width x depth as shown in the Figure 13, p. 46.

Subsistence fishfarming in Africa

45

Depth measurement

Lenght Width

Figure 13. Volume of a pond.

■■ WATER LOSSES

In addition to a leak in the drain, water losses can occur through infiltration into the substrate and evaporation.

¾¾ Evaporation

This component depends on the wind, the humidity of the air and the sunning, i.e. the climate of the area. Evaporation will be less strong under a cloudy sky than sunny (Figure 14 below). In equatorial zone, the water loss due to evaporation per day is about 2 to 5 mm height, which can be compensated by an addition from 15 to 35 liters of water per minute and ha of pond. In intertropical zone (25°N - 25°S), evaporation almost always exceeds 100 cm per year.

¾¾ Infiltration

The water losses occur through infiltration from the bottom of the pond and the dikes. If the dikes are well built, the principal loss will be done by the bottom. It will be also limited by the soil type. In general, the losses are more important during the first filling of a pond (Figure 15 below).

■■ FLOW OF THE STREAM

To have the maximum of profit from a pônd, it is necessary that the pond can be in production during all the year. There is a need for water throughout the year. It takes water to fill ponds and to maintain the water level. Water lost through evaporation and infiltration have to be compensated. It Clouds

Low evaporation

High temperature

Sun High evaporation

Low temperature

Figure 14. Water loss through evaporation by weather.

Figure 15. Water loss by ground.

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Subsistence fishfarming in Africa

Wind

2. SELECTIONS

1

2 Figure 16. Flow measurement for small rivers.

is during the dry season when there is little water, that the losses are large. To maintain water in a fishfarm of one hectare, it takes 2 to 5 liters water per second. This water flow is thus to control during the dry season. On the other hand, we must also check if there is no risk of flooding. People living locally are better informed. They know if there are significant flooding and water flows all year. You can also check the marks of water levels on the banks and bridges. A pond should not be built where there are risks of flood, for example too low to the bottom of the slope. Not only you can lose all the fish, but the dikes can be destroyed. We also look at whether the banks are planted, so with a water flow lower than if everything has been cleared along the riverbanks. The flow of a watercourse is measured in several ways. For low flows, one will just need a stop watch and a bucket (Figure 16 above). One channels all the water of the course to fill a bucket with known capacity and one measures the rate of filling. For more important flows, in the case of absence of adequate measuring devices, one will proceed as follows: (i) Determine the wet cross section S in m2 (Figure 17 below) with: S=lxp Where l is the width and p the depth. (ii) Use a stop watch and a half floating object to estimate the speed V in m.s-1 of the flood in regular zone AB of the stream (Figure 18 below): V = AB / t Where t is the time taken for the floating object to travel AB. (iii) Le flow D in m3.s-1 of the stream is defined by: D=VxS

l

S

A

B

p

Figure 17. Measurement of section of the river.

Figure 18. Measurement of speed V of the river.

Subsistence fishfarming in Africa

47

II.1.2. WATER QUALITY

One can have more water in quantity than necessary, but if its physico- chemical characteristics are not suitable with the fishfarming, fishfarm could not be established. An analysis of water is thus a prerequisite condition of the choice of the site. More simply, the observation of fish in a river in a natural state, during a rather long time, can constitute an indicator of good quality of water for fishfarming (Figure 19 below). Water is characterized both by the physical parameters (temperature, density, viscosity, color, turbidity, transparency), and by chemical parameters (pH, conductivity, alkalinity, hardness, dissolved oxygen, phosphorus, nitrogen ammonia, nitrites, nitrates, carbon dioxide…). In a general, the chemical analysis of water must be done preferably in dry season. The strong evaporation of water in this season allows the concentration of the various components present, which makes it possible to detect certain extremes. Quickly, some observations can be made without instruments. Water should not have a bad smell, neither bad taste, nor an unpleasant color; it should not be too muddy. Avoid the use of very turbid waters or heavily loaded with suspended particles (muddy water). Often, the water turbidity is caused by a too fast speed watercourse on a highly erodible land. However, one will be able to use water charged by implementing a settling tank upstream of the pond. It will be necessary moreover to take into account of the proximity of factories, because some industrial wastes can contaminate a water beforehand good quality and make it unusable for fishfarming. It is thus effluents: 99 Metallurgy factories, which reject lead, 99 Factories of electrolysis (manufacture of batteries for example) which rejects mercury, 99 Refineries which contain phénolés compounds, 99 Agro-alimentary factories as the breweries which can reject fertilizing substances, and which, to the extreme, can make water eutrophic and not very favourable with fishfarming. These effluents can kill fish or accumulate in their flesh, which presents a possible hazard for the consumers.

Ploughing can increase erosion  and cause silt to enter stream

Crops

Exhaust gases may  affect local rainwater Avoid wind drift of  spayed pesticides

A curtain of trees can  prevent these pesticides  from reaching ponds

Factories

New crops or new methods of planting  or harvesting may affect the quality of  runoff water from these field

Discharged waste materials may  contaminate water supplies

Roads or bridges may increase the  amount of silt or gravel in the stream

Pesticides Use interception ditches  to avoid pesticide runoff

Construction

Quarrying Gravel from quarry work  may block or alter the  course of the stream

Figure 19. Examples of factors that may affect water quality.

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Subsistence fishfarming in Africa

Curting concrete  near a stream may  affect water quality

2. SELECTIONS A

A

Disc 25 cm in  diameter

B

C

Weight

Strong string

Z

10 cm

10 cm

Finished disc and line

Knot

10 cm

10 cm

Disc Weight

Knot

Figure 20. Secchi disk. On left: Composition. On right: Transparency measurement:

A = point at which the disk disappears at the decent; B = point at which the disk disappears at the lift; C = mid-point between A and B, and Z = distance.

The usually measured parameters are the following: ÖÖ For the physical characteristics: color, transparency and temperature; ÖÖ For the chemical characteristics: pH, rate of dissolved oxygen, total and carbonated hardness, and very often, total phosphorus, nitrates and nitrites. Several types of devices are used for the measurement of these parameters. The transparency reflects the richness of water in natural foods or suspended particles. It is measured using the Secchi disc (Figure 20 above). If one does not have this material, it can be arranged by using a pole, a piece of paper of white polyethylene and a meter. The piece of white paper is fixed at the lower end of the pole that is vertically immersed in water. One measures the depth where the white paper disappears from the sight. One continues to immerse it. Then, one goes up and one again notes the depth to which one sees reappearing paper. The depth is evaluated by the average of the two readings. Total hardness translates the quantity of water soluble salts, particularly the ions calcium (Ca2+) and magnesium (Mg2+) important for the growth of the phytoplankton. A water is hard if its salt concentration is high, or soft. A water is regarded as good for fishfarming if it has a hardness ranging between 100 and 300 of calcium carbonate Mg (CaCO3). The water hardness translates in fact its capacity to be able to make precipitate some ions of alkaline salts, of which the ion sodium (Na+) of the soda (NaOH), used in the manufacture of the soap. Thus, if one does not have materials of performing the test, one washes the hands with soap by using a sample of water to be tested. It will be described as soft if it foams immediately and abundantly; it is hard if foam is difficult to come, possible foam disappearing little time after its appearance. Moreover, the dissolved salt traces remain visible on the edges of a stream of hard waters at the low water level when the usual level of water dropped much. The pH represents the concentration of water into hydrogen ions (H+), or more simply gives a measurement of acidity or alkalinity of water. Thus, water is neutral with pH = 7, acid if the pH is

Subsistence fishfarming in Africa

49

lower than 7 and basic if it is higher than 7. The majority of fish grow rather well in the range of pH from 6.5 to 9.0. All these parameters affect directly the development of natural foods. A water is for fish what the soil is for the plant. If it is of good quality or improvable, it is favourable for fihforming.

II.2. THE SOIL

The soil is a composition of living organisms, organic matters and minerals, water and air. According to their texture, structure and consistency, there exist various types of soils with more or less air and water. The physics soil characteristics determine its impermeability just as its capacity to ensure the stability of the dikes of the ponds, and its chemical characteristics influence the richness of water. They include texture (grain-size distribution), the structure (arrangement of the particles of the nondisturbed soil), the specific weight (concentration of the particles), porosity (proportion of the vacuums or interparticle spaces of the soil), the permeability (relative resistance of the soil to the passage of a water flow), compressibility (capacity to become deformed while decreasing by volume under the effect of the pressure), the shear strength (relative opposition of the soil to the shift), the color… The clay soils are often the best, taking into account their capacity to retain water and their high shear strength. A good soil for the construction of brick is in theory good for the construction of the ponds. The zone of the soil argilo-sandy, limono-silto-argillaceous, limono-argillaceous, limonosablo-argillaceous and argilo-silty is most desirable. The very sandy soils do not retain water, while the purely argillaceous soils are difficult to embank, and especially form not very stable dikes. A soil which contains too much sand or gravel will not retain water (Figure 21 below). The color of the soil gives an indication on the drainage of the soil and its composition. However, the marblings can appear for other reasons (Table VI below). If the marblings are brilliant colors, it is not a problem of drainage. If the marblings are mattes, usually gray, it is a sign of problem of drainage for a good part of the year. An abundant yellow clearly characterizes a sulphatic soil with an acid pH. Texture indicates the relative contents of different particles of size as sand, mud or clay. It allows to estimate the facility of work to be carried out, the permeability… For the construction of the ponds, the interesting soils are the argilo-sandy soils because they retain water easily. Pure clay, the laterite, the black humus and the peat are not good soils for the construction of the dikes. The black humus, the sandy peat and grounds are too porous except if one places a clay core to avoid the escapes. Pure clay, once dries, can be cracked. The laterite iosls are too hard. There exist simple tests to know quickly the soil texture. Table VI. Color of the soil and drainage conditions of the soil. Soil colour/mottling

Drainage conditions

Warm colours, browns, reds and oranges

Good drainage

Pale yellowish, pale and dark greys with rusty orange and/or grey mottling

Drainage seasonally poor. Water-table at 25- to 120-cm depth

Pale, dark and bluish greys, or pale brownish yellows with rusty orange, brown or grey mottling within the topsoil

Seasonally swampy soil. Water-table at less than 25-cm depth

Clay soil

Sandy soil

Figure 21. Impermeability of clay and sandy soils.

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Subsistence fishfarming in Africa

2. SELECTIONS

If the ball is falling apart,  the soil contains too much  sand

A - Make a ball

B - Throw the ball and  catch up with

If the ball remains compact, the soil contains  enough clay C

Figure 22. Test of the ball (I).

Coarse texture

Moderately coarse texture

Medium texture

Moderately fine texture

Fine texture 3 m

Figure 23. Test of the ball (II).

Subsistence fishfarming in Africa

51

A - Dig a hole

B - Fill it with water to the  top in the morning

C - Later, some of the water will  have sunk into the soil

D - Then fill the hole with  E - Cover the hole F - Result of the test the next morning water again to the top Figure 24. Test of soil permeability. A first test consists in taking a handful of soil on the surface and to compress it in the hand into a ball (Figure 22, p. 51). (A). Throw the ball in the air and catch it (B). The ball will disintegrate if the soil contains too much sand or gravel (C). If, on the contrary, it remains compact (D), the soil can be good for a pond, but, to be sure about it, one will have to carry out another test. Another test, close to the first, can be carried out (Figure 23, p. 51). Take a quantity of the soil in the hand, knead it, make mortar and produce a ball of it. Throw the ball on a vertical wall located at approximately 3 m of the operator. If the ball adheres to the wall, the soil is regarded as good for the dikes of ponds. It is even more appropriate that the degree of flattening of the adhered ball is low. If the ball does not adhere, but dislocates itself and fall, the soil will be judged of bad quality and thus non advisable for the construction of ponds. A more conclusive test can be carried out. One morning, it is a question of digging a rather deep hole where one will be able to hold until the waist (A). Then, one fills it of water to the top (B). The evening, a certain quantity of water will be infiltrated in the ground (C). One again fills the hole to the top (D). One recovers the hole with boards or branches (E). Lastly, the next morning, if most of water is still in the hole, it is that the soil retains sufficiently water to dig a pond (F) there (Figure 24 above). Whatever the other conditions, it is essential that the nature of the soil makes it possible to have a permanent water reserve. It must thus be sufficiently charged out of clays to obtain all the more large impermeability as the contributions of water will be irregular or weak. The objective is to have to compensate for only evaporation. The fact of having at its disposal a favourable topography and a sandy surface soil is however not harmful as long as a source of clay is available in the vicinity or in the basement close to surface. Indeed, even of very big hydroelectric dam see their dams built on the principle of the “clay Mask” recovering of the ground “All coming”. A sandy or humus-bearing soil is

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Subsistence fishfarming in Africa

2. SELECTIONS thus returned seals by contribution of a surface layer of 30 cm thickness clay. A rock ground is often difficult to work without mechanics, and is sometimes traversed by cracks which it is necessary to seal by clay. The chemical characteristics of the soil depends on the colloid concentration, the degree of saturation in exchangeable bases, the capacity of exchange cation or anion, the capacity to make available various biogenic salts… The soil must thus contain an amount of exchangeable minerals salts. This is possible if the soil contains a certain proportion of organic matters. The natural wealth of water is generally related to the richness of the soil which carries it. The acid soil are to be avoided, because this acidity can be transmitted to water and harm the growth of fish. It will be necessary in this last case to invest very heavily in quicklime in order to raise the pH of the water for its fishfarm use. The chemical composition of the water of the ponds depends primarily on the chemical characters of the soil which it crosses and of the vegetation which recovers them. In general water of savanna is richer and less acids than water emerging from the forest, but the risks of pollution by the sediments are greater (gullying, erosion). The richer the crossed grounds are in rock salt and the more water have then a strong natural productivity, because the proliferation of the phytoplankton and some higher plants.

swamps source land limit

land limit Figure 25. Identification of potential water supplies (A, K), drainage options (C, D, L, M, E, F), individual valleys (M level compare to D), comparison of the various good sites for the installation of ponds (IG, GH, ON), vision of the bottoms (CIRAD).

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53

Table VII. Topographical features for ponds. Slope in lenght

Slope transverse

Pond

Cost

High

High

None

Too high

High

Weak

Diversion

Reasonable

Weak

High

Dam

Reasonable

Weak

Weak

Sunken

High

II.3. THE TOPOGRAPHY

A viable construction of pond is possible only if the topography allows it. One of the general principles is to minimize the costs. For that, it is good that the water supply of the ponds is done by gravity, just as draining. Moreover, the dikes must be able to be built without much displacement of soil. Topography related, as we said it, to the forms and élévation of the considered land. One will speak thus about a flat ground or a rough ground, from a narrow and boxed or broad valley… Topography will determine the possibility to build ponds, their surface and their number (Table VII above). Once a zone is chosen, according to water and of the soil, it will be necessary to check various topographic parameters to confirm the potentiality of installation. It will be necessary to measure the zone, the slope, the elevation and the distance according to the source from water, the best way to supply the basins, the simplest way for the drainage. One will be able also better to thus apprehend the places to install the pond(s) (Figure 25, p. 53). The choice of the site for the construction of ponds in rough grounds will have to be done by having in mind the fact that future excavation will be able to balance approximately with the embankments. Moreover, the difference of height should be able to be developed in the supply and water gravitating draining of the ponds. The supply of water by gravity largely simplifies the installation of the ponds according to topography. The source of water must be located higher than the pond so that water can run out of itself in the pond (Figure 26 below). A soft slope will allow a good water run-off. This slope must have between 1 and 3 % (i.e. a difference with horizontal of 3 cm for a length of 100 cm). If the slope is too strong, one will have a too important runoff of water. If it is too weak, a dam will be necessary to store water, which will involve sometimes heavy additional work. Without slope, there is no flow of water, which will not allow drai-

Figure 26. Water supply by gravity.

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Subsistence fishfarming in Africa

2. SELECTIONS ning of the pond (Figure 27 and Figure 28, p. 55). To calculate a slope is rather simple and requires few materials (Photo A, p. 56, Figure 29 and Figure 30, p. 57). It is expressed as a percentage. A stake in top and a stake in bottom of the slope are placed. One horizontally tightens a rope between the two stakes using a plumb level. In absence of level, a bottle filled with water can make the level. This device is particularly practical, since it makes it possible to proceed quickly, even on an unequal grassy ground, and with a sufficient precision

A. Low slope (1 to 3%) Suitable

B. No slope How to empty the pond ? Unsuitable

Break of the dike High pressure C. Strong slope Unsuitable

Figure 27. Type of slopes and constraints.

A

B

C

Figure 28. Hill slope. A: Too high; B: Too high on one side, the second side if favourable; C: The two sides are favourables.

Subsistence fishfarming in Africa

55

(the maximum error is lower than 6 cm by 20 m of distance). It requires a team of three people. An observer installs a stake with the starting point A whose site is marked and maintains the rope on the graduation corresponding to h. The observer in B also maintains the rope against the same graduation, then upwards moves the cord on the second stake or to the bottom of the slope, until the person placed at the center indicates that the plumb level is with horizontal with the well tended rope. If one does not have a mason level, a water bottle can be enough. There H is known. It is then possible to measure the H-h difference. The slope P in % will be then: P = (H-h) x 100 / D With D = distance between has and B.

II.4. THE OTHER PARAMETERS

II.4.1. THE ACCESSIBILITY OF THE SITE

A good fishfarmer will daily control the pond. At least, he comes each day to survey the pond, he gives to eat per day to his fish if necessary. Each week, he reloads the composts, he cuts grasses on the dikes… It is necessary thus that the pond is not too far from the house of the fishfarmer and that there are no barriers between the pond and the house (river in rainy season, for example). It is advised to live more close as possible to its pond to supervise it against the thieves (Figure 31, p. 58).

II.4.2. THE POSSIBILITY OF BUILDING WITH LOWER COSTS

It was already seen that one will not build a pond where the slope is very strong because the downstream dike should be very large and thus expensive for a pond of reduced surface. For each work, one compares the required effort with the benefit which one can draw. If there are the choice, one thus will prefer an open site at a site full with tree trunks which are necessary to be remove with all the roots. One also will choose a ground without rocks or large stones.

II.4.3. THE PROPERTY LAND

It is a question of knowing the owner of the site on which will be established the future series of ponds. One will have to make prospection. One of the solutions is to require to the villagers to see by themselves which are the sites of proximity. Then, to evaluate the various sites according to the criteria above. In margin of the ponds, the maintenance or the plantation of the trees and other plant species will make it possible in very broken ground not only to protect the grounds against erosion, but also to consider the exploitation of the

Photo A. Measurement of a slope (DRC) [© Y. Fermon].

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Subsistence fishfarming in Africa

2. SELECTIONS ground on profitable way by considering by anticipation the various components of an integrated fishfarming with the other production of the rural world (grass for bovines, fruits as food or fertilizers in the ponds, zones really water full for cultures like rice,). The cleansing and the drainage of water in the majority of the swamp zones being difficult, these last will have to be selected for the construction of fish ponds by having in mind this constraint likely to encumber the costs with exploitation in the future.

Observer at the  back

Observer at the  front

Keep both ends of the rope at the  same height

Observer at the center

Figure 29. Measurement of a slope: Device.

D A

B

stake

rope

level

h stake H

H-h

Figure 30. Measurement of a slope: Calculation.

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57

Figure 31. Example of location of a pond in relation of the house.

ÖÖ The site selection have to take into account: ÖÖ The water: quantity and quality; ÖÖ The soil: impermeable; ÖÖ The topography: Weak slope and zone of emergence of sources.

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Subsistence fishfarming in Africa

Chapter 06

CHARACTERISTICS OF THE PONDS Once the choice of the villages then sites of installation of the ponds made, it now acts to set up the ponds (Figure 32, p. 60). The fish production is based on the use of earth ponds which contain freshwater, renews it, and allows the storage, the farming and the harvest of fish. The construction of the ponds and associated structures include adapted preparations and work, essential for the success of the exploitation. Moreover, the ponds must be inexpensive to build, easy to maintain and specific to ensure a good management of water and fish.

I. DESCRIPTION A fish pond is not very deep a water place, used for the controlled farming of fish. IIt is adapted to be easily and completely drained. It consists of (Figure 33 and Figure 34, p. 61): 99 The plate which is the bottom of the pond. 99 The dikes which surround the pond and are the walls making it possible to contain water. So they must be solid to resist to the pressure and impermeable. 99 The intake which is the structure to collect a quantity of water to feed the pond. 99 The emissary who is a river or a channel which allows the drainage of the pond. 99 The channels, which bring or evacuate the water of the pond: • The water arrival or supply channel which makes it possible to bring collecting water to the pond. • The draining channel or evacuation which is the work allowing the drainage towards the emissary. 99 The devices of regulation, which control the level of water or its flow through the pond, or both: • The water inlet which is the device designed to regulate the water flow towards the pond and which protects water from the floods. • The water outlet preferably a monk which allows the control of the level of the water and evacuation of the pond. 99 The outfall or overflow which allows the evacuation of the water excess of the pond and ensures the safety thus of it. 99 The filters, if necessary, which prevent animals and particles to come in and leave the pond 99 The fence which surrounds the pond and avoids the undesirable visitors. 99 Other structures of protection against ichtyophagous birds, if necessary. 99 The access ways and roads, which skirt the pond and make to reach it.

II. TYPES OF PONDS The piscicultural fresh water ponds differ according to the origin of water supply, the way of draining them, materials and processes of construction and, finally, the methods of fishfarm. The characteristics of the site in which they are built determine usually their characteristics. One can classify the ponds according to: ÖÖ The water supply. ÖÖ The drainage systems. ÖÖ The building materials. ÖÖ The type of use of the pond.

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0

Assessment Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Duration: 3 months

3 months

Selection Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Drainig channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas

Completion and filling in water

Duration: 6 - 9 months 3 to 6 months

Fish farming Fertilization

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Maintenance and  follow-up of the  ponds

Stocking with tilapia Follow-up  of the fishes

7 - 10 months

Stocking with  predators

Duration: 4 to 12 months

End of the cycle 11 - 22 months

Outside composter

Storage of  fishes

Draining of the pond  and harvest Sale and\or transformation  of the fish

Duration: 0.5 to 1 month

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Figure 32. Setting of fish pond: 3. Ponds.

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Subsistence fishfarming in Africa

Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

3. PONDS Regarding the use of the pond, it is certain that the same pond can be used for various uses according to the moments and the evolution of the structure installation. One will find: 99 Spawning ponds for the production of eggs and small fry; 99 Nursery ponds for the production of larger juveniles; 99 Brood ponds for broodstock rearing; 99 Storage ponds for holding fish temporarily, often prior to marketing; 99 Fattening ponds, for the production of food fish; 99 Integrated ponds which have crops, animals or other fish ponds around them to supply waste materials to the pond as feed or fertilizer; In this case, only the ponds usable for the subsistence fishfarming and which are the most viable ponds, will be considered. The principal characteristic will be that they are entirely drainable with running water available all the year. We will not take into account, ponds collinaires supplied with streaming or rainwater and the ponds of resurgence supplied with water of the ground water. We will focus the work on two types of ponds fed by a river: 99 Barrages ponds. 99 Diversion ponds.

Outside slope  of dike

Pond Inside slope  of dike

Outlet

Inlet

Monk Water  supply

Pond Crest Diker

Figure 33. Main components of a pond. Outside slope  of dike

Crest

Inside slope  of dike Monk

Water  level

Inlet

Water  supply

Outlet Dike

Pond

Figure 34. Cross section of a ponds.

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II.1. BARRAGE PONDS

The barrage ponds are ponds through which pass all the water coming from the source (Figure 35, p. 64). On a small river, one can block itt so that the water mass retained by the dam made a pond. In front of the dam, one installs a monk to drain the pond. One or more outfalls are expected to drain the excess of water in case of raw or strong rains. The outfalls must be able to evacuate even the strongest flooding, if not all the dam may be carrried. The most important point before beginning the construction of a barage pond is to know the maximum level and the maximum discharge of the river during the rainy season after a strong rain. On the great rivers which grow extremely in rainy season, it is preferable to make diversion ponds rather than barrage ponds. In addition to this lack of control on the water flow which enters the pond, one cannot either prevent the fish which live upstream of the river to enter in the pond. One cannot either put nets on the outfalls to prevent fish escape when the outfall work. Net may be blocked with sheets, branches and mud in suspension in water. Water will go up and can break the dike. One cannot correctly control the amount of water which crosses the pond: there are thus many risks of flood (food and fertilizer, fish loss when the flow of the river is important).

II.2. DIVERSION PONDS

Contrary to the barrage ponds, which retain all the water of the stream, the diversion pond use only part of water (Figure 36, p. 65). These are ponds through which passes a portion of water from the source and not all. The entry and exit of water in the pond are controlled. One thus will deviate part of the stream in a supply channel which will bring water to the ponds. The intake on the stream is usually built in front of a small dam of deviation. This dam ensures a constant water level in the supply channel. All the surplus of water which is not need passes by the outfall of the dam. The ponds supplied with a diversion channel can be built in parallel or series. The diversion ponds in derivation of the bypass type are built on the slopes of a valley and are primarily made up by three dams. These ponds are in general inexpensive, without risk of flood and well drainable.

II.3. COMPARISON

It is important to remember the following points:

ÖÖ Better control of the water supply means easier management of the pond, e.g. when fertilizing the water and feeding the fish. ÖÖ Better drainage also means easier management of the pond, e.g. when completely harvesting the farmed fish and when preparing and drying the pond bottom. ÖÖ A regular shape and the correct size makes a pond easier to manage and more adaptable for particular purposes. ÖÖ The choice of a particular type of pond will largely depend on the kind of water supply available and on the existing topography of the site selected. Practically, in spite of a higher cost, the increasingly intensive integrated management of the production of fish, will be better with diversion ponds (Table VIII, p. 63). Moreover, it will not be possible to extend the number of ponds with a barrage pond. This is important because that avoids blocking water of rivers which is also used by the villages located downstream. That can make it possible to avoid conflicts sometimes violent one.

ÖÖ Diversion ponds supplied with water by gravity are the most adequate approach proposed here.

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Subsistence fishfarming in Africa

3. PONDS Table VIII. Advantages and disadvantages of the barrage and diversion ponds. Type

Barrage pond*

Diversion pond**

Advantages

Disadvantages

•2Simple to design for small stream. •2Construction costs relatively low unless there are flood defence problems. •2Natural productivity can be high, according to quality of water supply.

•2Dikes need to be carefully anchored because the risk of break down in case of flooding. •2Need for a spillway and its drainage which be costly. •2No control of incoming water supply (quantity, quality, wild fish). •2Cannot be completely drained except when incoming water supply dries out. •2Pond management difficult (fertilization, feeding) as water supply is variable. •2Irregular shape and size. •2Sociological problems due to possible water retention towards the people living downstream.

• Easy control of water supply. •Good pond management possible. • Construction costs higher on flat ground. • Can be completely drained. • Regular pond shape and size possible.

• Construction costs higher than barrage ponds. • Natural productivity lower, especially if built in infertile soil. • Construction requires good topographical surveys and detailed staking out.

* If the barrage pond is built with a diversion channel, some of the disadvantages may be eliminated (controlled water supply, no spillway, complete drainage, easier pond management), but construction costs can greatly increase if the diversion of a large water flow has to be planned. ** Relative advantages will vary according to the arrangement of the ponds, either in series (pond management is more difficult) or in parallel (both water supply and drainage are independent, which simplifies management).

III. CHARACTERISTICS III.1. GENERAL CRITERIA

According to the needs, it will be possible to build a series of ponds with a management in shifted with shifted sowing, which allows monthly harvests, that is regular harvests during the year. Always with an aim of limiting the amount of work and the costs on the one hand, and of optimizing the availability out of water on the other hand, it will be necessary to lay out the basins according to topography. The development of a suitable site is consequently a complex exercise. A positioning in terraces makes it possible to arrange a surface much more important of ponds and to better keep water (Figure 37, p. 66). While seeking to position the downstream-dikes across the flow of water in the basement, it increases the availability of storage water of the site. A overall design of a site is essential to use surface as well as possible, the drop between the intake and draining and the availabilities of water. A provision of the ponds to the current does not maximize suitable surface (B): Surface in green is not used. This flow is carried out parallel to the water course. On the other hand, in the diagram (C), water is blocked in its flow perpendicular to the water course since all the ponds are on the same level. More water will then be stored in the basement above the plans of ponds. It will be available to fill the ponds again or to limit the losses during the dry season.

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63

Stream Spillway and overflow

Outlet Inlet to pond

Dam

Larger stream

Water intake

Outlet

Diversion channel Dam

Figure 35. Examples of barrage ponds.

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Subsistence fishfarming in Africa

3. PONDS

Outlet Larger stream

Pond Pond

Pond

Diversion channel

Pond Inlet

Larger stream Diversion channel Outlet

Pond Pond Pond Pond

Pond Inlet

Pond

Figure 36. Examples of diversion ponds.

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65

Stream

Stream

Water supply  channel

Water supply  channel

Stream

Equidistant  curve level Drain channel

A

B

C

Figure 37. Disposition of ponds in relation to the topography (CIRAD).

III.2. POND SHAPE

For an equivalent water surface, one will seek the shape of pond which minimizes the overall length of dam (Figure 38 and Table IX below). For a pond of the same dimension, the overall length of the dike increases regularly when the shape of the pond deviates gradually from the square to become more elongated. Meanwhile, the costs of construction increase. The dikes which separate the ponds (intermediate dikes) are narrower than the downstream-dike. The square form extend the downstream-dike (A). A too elongated rectangular form reduces it, but elongate in an important way the intermediate dikes (C). Moreover, if one wants to keep the same slope to guarantee a good draining, it will be necessary to dig more deeply. These two forms are not optimal (A and C). On a regular ground, the shape of pond which will require less work is rectangular but is not too much elongated (B). It is the form which will be used preferentially. In general, the rectangular ponds have a length approximately twice higher than their width. It is, also, better to use a standard width for the ponds planned for the same use. In several cases, it can be easier and more economic to adapt the shape of the pond to existing topography (Figure 39, p. 67). Table IX. Differents shape of a pond of 100 m2. Pond shape

Width (m)

Length (m)

square

10

10

20 + 20 = 40

7

14.3

14 + 28.6 = 42.6

5

20

10 + 40 = 50

2

50

4 + 100 = 104

rectangular

Dikes length (m)

Water supply channel

A

Intermediate dike

B

Downstream dike

Figure 38. Optimization of the surface / work (CIRAD).

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Subsistence fishfarming in Africa

C

3. PONDS III.3.

ACCORDING THE SLOPE

The orientation of the ponds will vary depending on the angle of the slope to minimize earthworks (Figure 40 below). 99 Slopes of 0.5 to 1.5%: The length of the rectangular ponds must be perpendicular to the level lines. This means that ponds must be oriented in the direction of the slope to the bottom follow the natural slope and is not necessary to dig the deepest part. 99 Slope greater than 1.5%: The length of the rectangular ponds should be parallel to the level lines. This means that ponds must be perpendicular to the slope. More the slope increases, more ponds must be reduced.

Dike Figure 39. Example of pond whose shape is adapted to the topography. Here, only two dikes are needed.

I = Inlet - O = Outlet 101.6

I 1.2

O

20 m

101.2

10 10

O

100.0 0.8

20

 m

I

O

I

O

I

100.4 100.0 99.2

99.2

0.6

101.2 20 m

99.6

99.6

10

101.6 100.8

100.4

1.0

10

I

O

100.8

Slope of 1 %

Slope of 3 %

Slope of 5 %

Figure 40. Disposition and shape of ponds according the slope.

III.4. LAYOUT OF PONDS

When one wants to install several ponds, there are two possibilities for positioning relative to each other (Figure 41 below): 99 In series: ponds depend on each other for their water supply, the water running from the upper ponds to the lower ponds. This system has the advantage of limiting the number of draining and

I = Inlet O = Outlet

Water supply I O I O

I

I

I

I

O

O

O

O

I

Drain O

I

O

A

B

Figure 41. Layout of ponds. A: In series; B: In parallel.

Subsistence fishfarming in Africa

67

supply channels of the ponds. However, the fact that it is the same water which passes in all the ponds can bring problems as for the propagation of diseases. Indeed, if a pond is contaminated, the risk of contamination of the others and to lose all its production is important. There will be also problems during drainings of the ponds. The required slope is also more important in total.

Photo B. Example of rectangular ponds in construction laying in parallel (Liberia) [© Y. Fermon].

99 In parallèle (Photo B, p. 68): The ponds are independent from each other, each one being supply directly from the supply channel. Water is not re-used after having crossed a pond. At contrario of ponds in series, it is possible to isolate without problems each ponds, and thus to limit the risks of contamination. Drainings are done independently and the slope is the same for all the ponds.

III.5. SIZE AND DEPTH OF THE PONDS

The ponds are characterized by their size, their form and their depth. We saw in au paragraphe II.1, p. 45 the calculation of the surface and the volume of a pond.

III.5.1. THE SIZE

The individual size of sunken ponds and diversion ponds can be decided upon by the farmer, considering the following factors (Table X and Table XI below): 99 Use: A spawning pond is smaller than a nursery pond, which is in turn smaller than a fattening pond. 99 Quantity of fish to be produced: A subsistence pond is smaller than a small-scale commercial pond, which is in turn smaller than a large-scale commercial pond. 99 Level of management: An intensive pond is smaller than a semi-intensive pond, which is in turn smaller than an extensive pond. 99 Availability of resources: There is no point in making large ponds if there are not enough resources such as water, seed fish, fertilizers and/or feed to supply them. 99 Size of the harvests and local market demand: Large ponds, even if only partially harvested, may supply too much fish for local market demands.

Table X. Size of fattening ponds. Type of fishfarming

Area (m2)

Subsistence

100 - 400

Small-scale commercial

400 - 1000

Large-scale commercial

1000 - 5000

Table XI. Resource availability and pond size.

Water

Large pond Large quantity

Rapid filling/draining

Slow filling/draining

Fish seed

Small number

Large number

Fertilizer / feed

Small amount

Large amount

Fish marketing

68

Small pond Small quantity

Subsistence fishfarming in Africa

Small harvest

Large harvest

Local markets

Town markets

3. PONDS Table XII. Characteristics of shallow and deep ponds. Shallow ponds

Water warms up rapidly Great fluctuations of temperature Greater danger from predatory birds Greater growth of water plants Smaller dikes needed

Deep ponds Water temperature more stable Less natural food availabl Difficult to capture fish in deep water Strong, high dikes needed

50 cm

150 cm

Figure 42. Maximal and minimal depth of a pond. In the situation of production fishfarming, one will choose ponds having a maximum of surface of 400 m2.

III.5.2. DEPTH

The fish ponds are generally not very deep. Their maximum depth does not exceed 1.50 m (Table XII and Figure 42, p. 69). The lower part should have at least 0.50 m in order to limit the growth of the watery plants. Deeper ponds are of a construction much more expensive because the volume of the dams increases quickly with the depth of the pond. However, it is sometimes necessary to use deeper ponds. In the dry areas, to store enough water to have in dry season for fish is essential.

III.6. DIFFERENCES IN LEVELS

In all the cases, there are some rules which it should not be neglected if one wants to have ponds easily manageable and completely drainable, supplied with gravity (Figure 43, p. 70). ¾¾ Water flows down from the highest to the lowest point (A). ¾¾ The water surface in a pond is always horizontal (B). ¾¾ The pond bottom should be above the water table at harvest (C). ¾¾ The bottom of the main water intake should be below the minimum level of the water source (D). ¾¾ The bottom of the feeder canal should be at or above the maximum pond water level (E). ¾¾ The pond inlet should be located at or above the maximum pond water level (F). ¾¾ The start of the pond outlet should be at the lowest point of the pond (G). ¾¾ The end of the pond outlet should be at or above the water level in the drain (H). ¾¾ The end of the drain should be at or above the maximum water level in the natural channel (I).

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69

A

B

C

Water supply channel

Water intake

Inlet

Inlet

D

E

F Drain channel

Outlet

Sream

Drain channel

G

H

I

Figure 43. The different points for the management of water by gravity. The explanations are given in the text.

In the case of a diversion pond fed from a stream through a main water intake and a feeder canal, it is easy to determine the difference in level ( (x) (cm) equired between minimum water level at the main intake and maximum water level at the end of the drain (Figure 44, p. 70). One preferably considers a pond a depth of 150 cm. It will be necessary to add there the difference in level necessary between the outlet of the drainage device of the pond and the maximum water level in the channel of draining (b) and the difference in level necessary between the water supply channel of the pond and the maximum water level in the pond (c) as well as the value between the entry and the exit of the drainage device of the pond (e). 1 1a

1b

2

3

4

c

5

6

7

7a

7b

8

9

a d

x

x b

1: Upstream - Water level: 1a: minimum - 1b: maximum 2: Main water intake: same level than upstream 3: End of intake channel 4: Pond inlet 5: Maximum water level in the pond

6: Top of dikes 7: Pond outlet - 7a: Start - 7b: End 8: Drainage channel 9: Downstream - Maximum water level

x = The difference in level required between the minimum water level at the main intake and the maximum water level at the  end of the drainage channel a = The difference in level required between the top of the dikes and the maximum water level in the pond b = The difference in level required between the end of the pond outlet and the maximum water level  in the drainage channel c = The difference in level required between the pond inlet and the maximum water level in the pond d = Maximum depth of the pond (150 cm minimum)

Figure 44. Level differences.

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Subsistence fishfarming in Africa

3. PONDS x > 150 + b + c + e This minimum of difference in level is essential to have completely drainable ponds.

IV. SUMMARY ÖÖ We will choose: ÖÖ Diversion ponds, ÖÖ Rectangular, ÖÖ Arranged in parallel, ÖÖ Size of 100 to 400 m2, ÖÖ Supply with water by gravity. The ponds will thus be laid out according to a diagram like that indicated on Figure 45 below. Examples are presented Figure 46, p. 72. Stream

Water  supply

Stream used as  diversion channel

I O I O I O Water supply  channel outflow in  the stream

Water supply  channel I

O I

O O

I I    = Inlet O   = Outlel

Figure 45. Classical plan a diversion ponds.

Subsistence fishfarming in Africa

71

Stream

Natural diversion  channel

Water supply  channel

A

Stream

Water supply  channel

Diversion  channel

B Figure 46. Examples of diversion fishfarm. • Water supply by a stream • One (A) or two (B) row(s) of ponds in parallel • A natural diversion channel • Optimal water control

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Water supply  channel

Chapter 07

THE CONSTRUCTION OF PONDS Once the site is chosen, it acts to carry out the construction of the ponds and the associated structures (Figure 47, p. 74). As we saw in the previous chapter, we will be interested here only in diversion pond which is the preferential type to use, but it is clear that these steps are the same ones for another type of pond. It is, however, important to perform this work in dry season. To build ponds of quality, it is necessary to complete work by steps and in a certain more or less strict order which is briefly described here for a diversion pond of the bypass type. 1. 

Laying out plan

2. 

Cleaning of the site

3. 

Water supply channel

4. 

Draining channel

5. 

Staking out the pond

6. 

Building the dikes

7. 

Pond bottom drain laying out

8. 

Building inlet, outlet and filtration

9. 

Décantation pond

10.  Other structures: Erosion fight, biological plastic, fence 11.  Filling in water and test

I. THE DESIGN PLAN With this stage, one studies one or more possible localizations of the ponds. A first selection is taken minimizing work compared to clear surface. The design is progressive: The assumptions formulated on the filling and the diversion of water are progressively evaluated as to the completion of construction. The criteria which will be observed throughout installation are mainly: 99 Rise of ground water; 99 The tightness of the dam downstream dike; 99 The behavior of overflows and monks during the flood; 99 The feasibility of the work; 99 Interactions that develop with the surrounding facilities (bins, gardening). An initial plan is proposed (Figure 25, p. 53 and Figure 48, p. 75). It is a question of writting measurements of lower slope and of locating on the plan the position of the various structures to be developed. Initially, one will partially clean the ground with cutter for a better viewing. Then, one will proceed to the survey of the site. In a general way, this survey is done methodically, with a regular spacing between the measure points. Each point is materialized on the ground using a level stake. A letter corresponding to the same letter on the future topographic chart is written on the top of the stake. Spacing between the points will depend on the topography of the ground. If the ground is very undulated, the points will be very closed. The first point can be take on the position of the collecting point. The line of greater slope may be determined as it has been show in paragraphe II.3, p. 54. For that, the highest point will be located, then the lowest. Then one will calculate the slope between these two points.

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0

Assessment Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Duration: 3 months

3 months

Selection Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Drainig channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas

Completion and filling in water

Duration: 6 - 9 months 3 to 6 months

Fish farming Fertilization

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Maintenance and  follow-up of the  ponds

Stocking with tilapia Follow-up  of the fishes

7 - 10 months

Stocking with  predators

Duration: 4 to 12 months

End of the cycle 11 - 22 months

Outside composter

Storage of  fishes

Draining of the pond  and harvest Sale and\or transformation  of the fish

Duration: 0.5 to 1 month

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Figure 47. Setting of fish pond: 3. Ponds.

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Subsistence fishfarming in Africa

Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

3. PONDS

swamps source

land limit Staking out  the channel

Staking out dikes  and slopes

land limit Figure 48. Visualization by picketing of the first plan of possible water supply (A, K), possible drainage (C, D, L, M, E, F), of differents valley (level of M towards D), (Figure 25, p. 53) (CIRAD). In red, limite of work. The line of greater slope makes possible to establish the various structures of the fishfarm so that they are most functional possible, particularly from the point of view of the drainage and water sanitation. The arrangement of the various structures on the topographic map will have to be done by taking into account the cost of construction and operation of the future farm, safety requirements of work, and probable future extension of the farm.

II. THE CLEANING OF THE SITE After having delimited and visualized the future site of the fishfarm, the first work will be to clean this zone. It is necessary to define in a precise way the concerned zone before starting to clear, then, to determine the external corners of the surface containing the ponds, which must completely include the surface occupied by the dikes. One can delimit this zone by stakes out of wooden, ropes or posts. Once this task is achieved, it is necessary to delimit an additional surface, beyond the dikes, which will be used as passage and working area around the site. One is then ready to start (Figure 49, p. 76). That start with: ÖÖ Clear the zone including the dikes of the ponds by removing it of all the vegetation, the shrubs, the trees (including roots and stocks) and of all the large stones. ÖÖ Clear the passage and working area around the dikes. ÖÖ Clear all the trees and shrubs on a area of 10 m around the dikes and the works, around the access roads and the installations of water supply and drainage.

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75

Delimit an area then   clear it completely,  including a zone of  passage from 2 to 3 m

Remove the shrubs  and the trees on an of  10 m around

Remove all the  vegetation

1

2

Figure 49. Preparation of the site of the pond. All the grasses have to be cutted as for the culture. All the trees must be cutted and their roots removed. If roots are left, the pond will eventually seep. The grasses, the shrubs, all organic matters and the rocks must be removed. One will be able to burn if that is possible. The ground must be very well cleaned before the construction itself does start. Among the elements to be removed, one will find (Figure 50 below and Photo C, p. 77): 99 Woody plants (A), where the roots can cause serious cracks in the fishfarm structures like the devices of water supply and draining. 99 Stocks of trees (B), whose decomposition can weaken the structures by leaving vacuums in the ground. 99 Large stones and rocks (C), whose extraction can prove to be necessary. 99 Termite mounds and burrows of animals (D), which must be completely removed. Then it is necessary to fill the hole created with clay. Tree stump

B Rocks and stones Shrubs and trees

C Termite mound

A

Burrow

D

Figure 50. Cleaning of the site. A and B: Trees; C: Rocks and stones; D: Animals habitats.

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Subsistence fishfarming in Africa

3. PONDS

Photo C. Cleaning of the site. On left: Tree remaining nearby a pond {To avoid}(DRC); On right: Sites before cleaning (Liberia) [© Y. Fermon].

III. WATER SUPPLY: WATER INTAKE AND CHANNEL The water supply includes water intake, the main channel and the small canals which bring water from the main channel to the pond. The principal water intake are used to regulate overall and to derive the water supply from a pond or a group of ponds. They have primarily the role to ensure a regular water supply, which may be regulated according to the present conditions. The water inlets are settled, if possible, against the water current to prevent the transport of material that the river carries, to the ponds. This canal fed in theory by a constant flow, but adjustable, is made to bring water to the upper part of the ponds built so that their complete draining can be made whatever the level of water in the bottom of the valley. This condition is very important and must be strictly respected. In too often cases where it is not, the ponds are just simple diverticula of rivers whose flood demolish the dike and where the fish enter and leave easily. One makes some surveys to see whether it does not arise particular difficulties (presence of rocks in particular). The main elements of a water intake are: ÖÖ A diversion structure being used to regulate the level of the watercourse and to ensure that it is sufficient to feed the water intake without drowning. ÖÖ A device of regulation of the level of entry (and flow) inside the structure itself, being used to regulate the water supply of the ponds; such a device is generally connected to the transport of water structure; ÖÖ A structure of protection of the entry, for example stilts to prevent any deterioration of the water intake due to the debris. One will use an open or free level water intake in which the levels of supply are not controlled and where the water catch functions under all the conditions of flow. This system is simple and relatively cheap, but it generally requires a reliable water supply which does not vary too much.

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The important points to take into account are the following (Figure 51 and Table XIII below): ÖÖ The levels of the source of water supply (river, small river…) related to the water supply structure and the ponds themselves. ÖÖ The depth to which one wishes to collect water (surfaces, low or on all the depth of the water source). It will have to be made sure that the water level in the supply source is always sufficient to take water with the desired depth. It also should be made sure that the water intake is not likely to be drowned. The broader the water intake is, the less the pressure loss will be strong when water runs towards the ponds. This factor can have importance in the event of very weak load. In the majority of the cases, however, the water intake has approximately the same width as the supply channel which is connected to him. The size of the supply channel is fixed according to the desired flow. If the supply channel is particularly broad, or if one wants to increase the pressure loss on the level of the water intake (for example, if the external level of water is definitely higher than that necessary in the supply channel), the water intake can be narrower than the supply channel. In general, a narrower intake is easier to regulate. For that, one can install structure simple to build. After selecting the water intake, the supply channel which will bring water into the ponds have to be arranged (Figure 52, p. 79). This channel has a very weak slope and must be able to bring water throughout the year. One chooses the layout of the channel by stakes a level line on the basis of the base of the water intake until the site where the ponds will be built. Practically, after having established the layout of the level line, one adopts a definite location according to the ground.

A

Stream

Main water  supply 

B

C

The water level decrease  with the distance

D

F

E

Inlet of the pond

Pond

A: Minimum-maximum water level in the stream and in the first part of the channel B: Charge loss C: Minimum-maximum water level in the last part of the channel after the charge loss D: The level of the inlet of the pond have to be lower than the minimum water level in the channel E: The maximum water level have to be check to avoid flood F: The release of the inlet is at 10 cm over the maximum water level of the pond Figure 51. Water levels differences. Table XIII. Diversion structures to control stream water levels. Type of stream

Small

Large

78

Flow less than 10 liters/ secund

Structures required Of diversion Not to be submerged

Dikes in earth Wood/ropes/clay Wooden fence

No significant flood conditions

No need

-

Water flow at least twice the flow required

Of diversion To rase water level

Wood or stones dikes, adjustable

Significant flood conditions

No need

-

Subsistence fishfarming in Africa

3. PONDS

Staking out Water supply channel

Final layout

Figure 52. Setting of the water supply channel. It is always necessary to avoid giving a too strong slope to the channel and providing if necessary, stones or concreted falls. Then, one carries out the digging and the sloping of the channel. Remember that the channel should be dug dry. The method consisting in digging a channel as water penetrates there, is to be avoided because it systematically results in giving a slope too much strong to the bottom of the channel. The channels without sealing surface have most of the time a cross section of trapezoidal form, defined by the following elements (Figure 53 below): 99 The width (b) of its bottom (or ceiling) horizontal; 99 The slope (z/l) of the side walls; 99 The maximum depth of water (h); 99 The revenge (f) allowing to avoid any overflow. The dimensions of the channel are indicated in Table XIV, p. 80. It is essential that the current speed in the channel does not involve the erosion of its walls. The maximum speed of water varies with the nature of the ground: 0.15 m/s in the fine ground and 1.00 m/s in stones. If one cannot follow the level line for an unspecified reason and that one must reduce the level of the channel, it is necessary to envisage an oblique fall or or a pipe, but one should not in no case give

Water level

Slope z/l (1.5/1 ou 1.5:1)

f

h

l (l = 1) z (z = 1.5) b Figure 53. Transverse profile of the channel. Measure and slope of sides.

Subsistence fishfarming in Africa

79

Table XIV. Channel dimensions. Small farm

Medium farm

A few l/s

20-50 l/s

Bottom width

20 to 30 cm

50 cm

Water depth

20 to 40 cm

60 to 80 cm

Side slope

1.5:1

1.5:1

Top width

60 to 100 cm

150 to 180 cm

Bottom slope

0

1 ‰ (1 cm per 10 m)

to the channel a too strong slope. So, despite these precautions, the water of the channel is turbid, it should be provided on the water course of the mud tanks or conceived widenings in such way that the current velocity is enough low there, to allow the deposit of the suspended matter. After the last checks of the definite location, one can carry out the earthwork of the dry channel, while starting where one wants, according to the needs for the moment. This operation is done in three times (Figure 54 below): 1. First, to dig the central part with distant vertical walls of a width equal to the width of the bottom, then one adjusts the slope longitudinally along the bottom, and one proceeds to the cut of the slopes (sloping). 2. Be carefull to leave in place (in the axis or on the edges) the stakes whose tops must be used

Cnttre line Leave 10  cm of earth  at the  bottom Mark the  line of the  channel  with centre,  slope and  bottom  stakes

Cut out sides of channel

Centre line Dig out  remaining  10 cm of earth

Bottom width

Bottom width

Bottom width

Move the rope  out to the slope  stakes Leave  sections of  earth

Rope Stretch a  rope along  the bottom  stakes

Rope

Cut out sides of  channel

Remove  sections of  earth Check  cross-section  with wooden  gauge

Remove centre  and bottom  stakes

Masons level

Stakes

Figure 54. Channel digging. Photo D. Channel during the digging (Liberia) [© Y. Fermon].

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Subsistence fishfarming in Africa

Final channel  bottom

3. PONDS as reference mark for the depth and to reject the excavated materials downwards in order to avoid a possible overflow during floods. 3. One adjusts the slope longitudinally to the bottom. When, in certain places of the course, the channels must be deepened, the same gauge is used to check as the constant width of the ceiling and the regular slope of the banks was respected strictly, in the major part of the channel. Conversely, when the channel must pass by some high points and hillside, the depth of the earthwork will be lower and the installation of a bench on the side of the channel is necessary. This one will be built out of perfectly compacted ground and the peak, of a sufficient width, will have to reach everywhere the same level above the wetted cross section. The installation of the water falls intended to bring back the slope of the channel to the acceptable maximum, must always be made before the first setting in water, in order to eliminate all the risks from erosion. On the other hand, the installation of the overflows, the settling basins and the ditches of guard for the drainage of rain, if they are necessary, is less urgent. To finish, it should be noted that the process which consists in digging a channel (backwards) by small sections starting from the river until the sufficient depth so that water runs there, systematically leads to give too much slope to the channel. This process is not dadvisable.

IV. DRAINAGE: CHANNEL OF DRAINING AND DRAINAGE The site and the layout of the channel of draining are in general easier to determine (Figure 55 below). The ponds must be able to be emptied throughout the year without remaining there any water pool. For that, it is necessary that the bottom of the channel of draining is much lower than the bottom of the pond (Figure 56 below). This channel is built, generally, once the pond finished. However, it is included here because the way of carrying it out is identical to that of the supply channel. To take the bed of the valley as channel of draining is risky. Indeed, if during the floods, the water level in the valley is higher than the bottom of the pond, one will not be able to use the bed of the valley like channel of draining. If, on the contrary, this water level is permanently lower than the bottom of the pond, one will be able to use the bed of the valley like channel of draining. It is also preferable to set up a channel of drainage around the zone of the ponds. Now, the following stage will be to fix the site of the ponds on the area between the supply channel and the position of the channel of draining.

Water supply channel

Location of the pond

A Lower level than that of the pond

Drain channel

B Sometimes upper than that of the pond

Figure 55. Setting of draining channel.

Figure 56. Level of draining channel.

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81

V. THE PICKETING OF THE POND On the area delimited by the draining and water supply channels, one can now delimit the ponds. This operation is called the picketing or staking. It must allow to represent the site of the dikes as well as dimensions and the heights of the dikes with stakes. It will thus be necessary to respect, thereafter, these dimensions during work (Figure 57 below and Photo E opposite). The staking is done using stakes which must have a sufficient height to allow spoil or fill later without risk to discover the buried ends or to cover the air ends. One will on the whole have 4 rows of pegs for the main dike and the 2 side dikess and 3 for the upstream dike. These stakes will be spaced from each other of 2 m. A spacing between the rows of pegs will be function of dimensions of the dikes.

Water supply channel

Photo E. Stakes during the building of the dikes (Liberia) [© Y. Fermon].

Water supply channel

Location of the pond

Location of the pond

Drain channel

Figure 57. Picketing of the pond and the dikes.

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Subsistence fishfarming in Africa

Drain channel

3. PONDS Intermediate dikes   between neighboring ponds

Upstream

Downstream

Lateral Peripheral dikes

Figure 58. Cleaning of the zones where the dikes will be build.

Figure 59. Definition of the different types of dikes.

VI. THE CONSTRUCTION OF THE DIKES It is not enough to dig a hole to have a pond: after having delimited the site of the pond, it is necessary to build carefully the quite tight dikes around. The dikes are the essential parts of the pond, on them will depend solidity on the pond, its capacity to retain water… It should be remembered that it is necessary, initially, to remove the plate of the pond and the site of the dikes of all the debris which could be there: roots, plants, stones… One also removes the surface layer of the ground, (i.e. the layer of cultivated ground), where the dam must be built, to avoid the water escapes through the base of the dike when the pond is underwater. Most of the time, one forgets to strip the ground before the construction of the dikes. This almost always causes important water escapes and consequently, an increased requirement of water (Figure 58 above). For a diversion pond, one distinguishes (Figure 59 above): 99 The upstream dike parallel to the supply channel, 99 Lateral dikes, perpendicular to the upstream dike and the main dike and supporting on their walls (berms), the pressure of water from two nearby ponds, and Crest 1 m

Height 1 m Extern Intern

2 m

1 m

1 m Side

Base

Figure 60. Description and proportion of a dike (of 1 m high).

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83

99 The main dike, that downstream, which supports of its slope upstream the greatest pressure of water of the pond. The latter must be thickest and highest. A dike comprises five principal parts (Figure 60 below): 99 The foundation or bases, 99 The body, 99 The bench or top, 99 The slopes, 99 The height. Any dike must have the following properties: ÖÖ It must be able to resist the water pressure created by the height of the water mass retained in the pond (Figure 61 below). ÖÖ It must be sufficiently high to prevent water from flowing out, which would quickly cause to destroy it (Figure 62 below). ÖÖ It must be impermeable, and the infiltrations through the dike must be reduced to the minimum. If the soil contains a lot of sand, it is advisable to trench in the center, throughout each dike, to the layer of impermeable ground, in order to replace the sandy and permeable ground by an impermeable clay core which goes until the top of the dike. The dikes thus built are tight and more solids. This technique of anchoring of the dike wich not request too much work is advised for construction of ponds and whatever the type of soil used for construction (Figure 63, p. 85). It is generally useless to provide an intermediate dike, which separates two ponds, a solidity comparable with that of a peripheral dike, insofar as the water pressure is practically equal on both sides. However, if a pond should be emptied whereas the other remains full, the variations of pressure will be close to those observed on the peripheral dikes, and will have to be envisaged a more solid construction. The dimensions of the dikes depend on the surface of the pond. The foundation of the dike is function of the height of water in the pond. The slope of the embankment is function of the quality of the soil. It can thus vary from 1 per 3 (that is to say 33 %) for a soft ground to 2 per 3 (66%) for a Unequal water pressure

Equal water pressure

Stronger dike  needed

Dike may be less  strong

Figure 61. Pressure difference on a dike. Strong rainfall

Strong rainfall High dikes

A

Dikes break down

Water go inside the pond

B Figure 62. Dikes. A: Good high; B: Dikes too small.

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Subsistence fishfarming in Africa

Fish escape

3. PONDS

Figure 63. Digging of the cut-off trench for clay core. Clay core lowers saturation line  Water line 8:1

Hydraulic  gradients 4:1 8:1

Clay core

Figure 64. Clay core and saturation of the dikes. Freeboard (25 - 100 cm)

Settlement (dike heigh lost)

Depth of water

Figure 65. High of a dike. Depth; Freeboard; Settlement.

(15%)

SH FB (30) CH

{153} DH WD (130) (100)

Figure 66. High of the structure (definitions and example in the texte).

soil of better bearing pressure. The bench or top of the dike must have a width higher than 1 m to allow later handling of the seine during fishings. An establishment of the dike starts with the establishment of the foundation. The downstream-dike which surround the fishfarming site is the object of a pressure exerted by the water of the ponds. Water saturates the soil in bottom with the dike (Figure 64, p. 85). The downstream-dike must be made consequently to avoid any infiltration. On the sandy soils, it must have a base broader than on the argillaceous soils. When water, in its way, meets a ground water located low, the water of the basement of the pond is in balance with the expanse of water since it lost its pressure. In this successful case, there is no more infiltration once the water-logged soil with water. The calculation of the height of the dam to be built should take into account (Figure 65 opposite): 99Desired depth of water in the pond. 99Freeboard, i.e. upper part of the dike which should never be immersed. It varies from 25 cm for the very small ponds in derivation to 100 cm (1 m) for the barrage ponds without diversion canal. 99The dike height that will be lost during settlement, taking into account the compression of the subsoil by the dike weight and the settling of fresh soil material. This is the settlement allowance which usually varies from 5 to 20 % of the construction height of the dike. Accordingly, two types of dike height may be defined (Figure 66 opposite): ÖÖThe design height DH, which is the height the dike should have after settling down to safely provide the necessary water depth in the pond. It is obtained by adding the water depth and the freeboard. ÖÖThe construction height CH, which is the height the dike should have when newly built and before any settlement takes place. It is equal to the design height plus the settlement height. The construction height (CH in cm or m) simply from the design height (DH in cm or m) and the settlement allowance (SA in %) as follows: CH = DH / [(100 - SA) / 100]

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If the maximum water depth in a diversion pond of medium size is 100 cm and the freeboard 30 cm, the design height of the dike will be DH = 100 + 30 = 130 cm. If the settlement allowance is estimated to be 15%, the required construction height will be: CH = 130 / [(100 - 15) / 100] = 130 / 85 = 153 cm. A dike rests on its base. It should taper upward to the dike top, also called the crest or crown. The thickness of the dike thus depends on: ÖÖ The width of the crest; and. ÖÖ The slope of the two sides. The dike must make 4 m at the base for a minimum 1 m of height, globally. The slope of the dike at the bottom of the slope of the pond is more important to limit erosion and to allow an easier access to the bottom of the pond (Figure 60, p. 83, Figure 66 and Table XV below). The width of the top of the dike is related to the depth of water and the part which the dike must play for circulation and/or transport: Table XV. Examples fo dimension of dikes. Surface (m2) Quality of soil

200

400 - 600

Good

Fair

Good

Fair

Water depth (max m)

0.80

1.00

Freeboard (m)

0.25

0.30

Height of dike (m)

1.05

Top width (m)

1.30

0.60

0.80

1.00 1.5:1

Dry side, slope (SD) (outside)

1.5:1

2:1

Wet side, slope (SW) (inside)

1.5:1

2:1

2:1

Base width (m)

4.53

6.04

6.36

8.19

20

20

15

15

1.31

1.31

1.53

1.53

3.36

4.48

5.63

7.26

Settlement allowance (%) Construction height (m) Cross-section area (m2) Volume per linear m (m2)

Crest Crest width at least  equals water depth

(> 1.00 m)

(1.00) (0.40)

Dry side  slope

Wet side slope Water  depth

{1.5:1}

{2:1}

Clayey soils Increase as sand increase

Figure 67. Dimension of a dike.

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3. PONDS Table XVI. Expression of values of slope according the chosen unit.

1 m

1 m

Slope

1 m

1 m

1 m

1 m

1 m

Ratio

Pourcentage

Degrees

1:1

45

100

3:1

1.5:1

34

66

2:1

27

50

1 2:1 1.5:

2.5:1

22

40

3:1

18

33

1 m

1.5 :

1 m

1

1.50 m

1: 1

1 m

1 m

Axe

Figure 68. Calculation of the slope of the dikes.

ÖÖ It should be at least equal to the water depth, but not less than 0.60 m in clayey soil or 1 m in somewhat sandy soil. ÖÖ It should be even wider as the amount of sand in the soil increases. ÖÖ It should be safe for the transport you plan to use over it. In individual ponds, dikes have two faces, the wet side inside the pond and the dry side or external side (Figure 67, p. 86). These two sides should taper from the base to the top at an angle that is usually expressed as a ratio defining the change in horizontal distance (z in m) per metre of vertical distance as, for example, 2:1 or 1.5:1. In a dike with side slope 2:1, for each 1 m of height, the base width increases on each side by 2 x 1 m = 2 m. The side slopes of each dike should be determined bearing in mind that: 99 The steeper the slope, the more easily it can be damaged; 99 As the soil becomes more sandy, its strength decreases, and slopes should be more gentle; 99 As the size of the pond increases, the size of the waves increases and erosion becomes stronger; 99 As the slope ratio increases, the volume of earthwork increases, and the overall land area required for the ponds increases Usually side slopes of dikes vary from 1.5:1 à 3:1, which 18° to 45° (Figure 68 and Table XVI above), depending on local conditions for ponds of 100 to 600 m2. The slope of the dry side can be made steeper than the slope of the wet side. The care taken to the construction of the dikes is an essential component of the lifespan of the ponds (Figure 69, Figure 70 and Figure 71, p. 88 and Photo F, p. 89). To build the dikes, one digs the ground of the major part of the pond: one removes the too sandy ground (A). The good argillaceous soil is transported and compacted wet, by a compactor or while rolling a barrel of 200 l filled with water on the site of the dikes. Each layer of good 10 cm thickness wet argillaceous soil (not containing vegetable nor large stones) is vigorously rammed (B). If one rams a layer of too thick soil, the ground will not be well packed in-depth. The ground will be well compacted and dikes well seals if the dikes are built according to this technique called “in staircase”. One uses a compactor, a barrel, or a roller for compacting each stair well, one after the other. The majority of the water escapes are due to a bad compaction, in particular above the outlet. Each stair, of decreasing width from the bottom to the top, is rammed and compacted vigorously (C). After having assembled the dike, step by step, until the height of desired water (0.6 to 1.2 m) according to the type of pond (laying, stocking with fish, parent) and without forgetting the height of the freeboard of 0.25 m, it is enough to flatten the edges of the steps with a wooden handle. In the very argillaceous soils, the soil is more difficult to work and some prefer to build the dikes with blocks of ground which they cut in the ground. The sandy grounds are easier to work and are crumbled in the hands: they are very permeable and are less appropriate for fishfarm (D). To build dikes on clay soils, one proceeds in the same way, (method of the staircase) but one moves the ground by cut mound, removed the vegetable top layer and the large vegetable debris (E). With a little water, each argillaceous lump of earth is sticks to neighboring clumps and form a solid and impermeable paste, which strongly adheres to the clay soil on which the dike is built. One often forgets

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A

B

C

D

E

F

Figure 69. Construction of the dikes (I). A, B and C: Traditionnal; D, E and F: By blocks. Water supply channel

Water supply channel

Drain channel

Figure 70. Construction the dikes (II).

Drain channel

Figure 71. Preparation of the bottom.

to clean the lumps thus causing useless water escapes through the dikes. After having deposited side by side the lumps of earth all along the dike to be built, one sprinkles and one crushes each stair over all his length so that each argillaceous lump of earth is stick to its neighbors (F). Moreover, one will use a roller or a barrel of 200 liters filled with water or a compactor for compacting the dike well over all his length. If the dikes of the pond are well built with adapted soil, the pond will be able to last more than twenty years with little maintenance. Either during construction, one leaves space for the structures of inlet and outlet, or those are made at the same time. One will see later on how to build them. Once the dikes are built, one will be able to deal with the plate or bottom of the pond.

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3. PONDS

Photo F. Dikes. On left: Slope badly made, destroed by erosion (DRC)[© Y. Fermon]; On right: Construction (Ivory Coast) [© APDRA-F](CIRAD).

VII.

THE DEVELOPMENT OF THE PLATE (BOTTOM)

The pond having to be completely empty without remaining water puddle pools there, one arranges the bottom or the plate in soft slope towards the outlet (Figure 72 below). The construction of the bottom of the plate is done by clearing the bumps to remain slightly in top of the projected dimensions. For the embankments, a particular care is given here to the compaction and the choice of the quality of the soil to be used, because one is in a case similar to that of the supply channel which is permanently submerged. In the case of small ponds, the bottom must be with a soft slope (0.5 to 1.0%), since the water inlet to the outlet, to ensure an easy and complete dry setting of the pond. One must always make sure that the entry of the outlet is slightly below the lowest point of the bottom of the pond. For the ponds whose surface is rather important (more than 4 ares) the installation of ditches of drainage towards the emptying device is very useful. It is preferable to ensure a complete dry setting by a network of not very deep ditches of draining and having a slope of 0,2 %, rather than to seek to create a slope on all the plate of the pond. When the bottom of the plate is entirely regularized, one will carry out the digging of the drains converging of the edges towards the zone of draining. The drains are small channels built to facilitate I = Inlet O = Outlet

I

I

I

O

A

B

O

C

O

Figure 72. The bottom or plate. Direction of the slope (A) and drain setting: In ray (B); As «fish bones» (C).

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the total evacuation of water. All the various operations are carried out by respecting the data of the plan and the level stakes. One can lay out the drains (Figure 72, p. 89): 99 In ray starting from the outlet, or 99 In “fish-bones”. The ditches of draining must be all connected to a harvesting pit dug in the deepest part of the pond, usually in front of the outlet, where all the fish can be gathered for harvest (Figure 73 below). It is necessary not to forget to include the following differences in level (Figure 74 below): 99 Between the end of the ditch of draining and the bottom of the harvesting pit (at least 20 cm). 99 Between the bottom of the harvesting pit and the bottom of the outlet (at least 10 cm).

VIII. THE CONSTRUCTION OF THE POND INLET AND OUTLET It is a question, here, of seeing which are the inlet and outlet of the water of the ponds, i.e. how to get water in the ponds and how to empty them completely, while managing these inflows and outflows of water.

VIII.1.

POND INLET STRUCTURES

Inlet structures are built to control the amount of water flowing into the pond at all times. There are three main types of inlet structures: 99 Pipe inlets, 99 Open gutter inlets, 99 Canal inlets. When designing and constructing an inlet structure, one should pay particular attention to the following points: (Figure 75, p. 91): ÖÖ The inlet have to be placed at the shallow end of the pond. Harvesting pit Monk

ÖÖ The bottom level has to be at the same level as the bottom of the water supply channel and ideally at least 10 cm above the maximum level of the water in the pond. ÖÖ The inlet structure have to be horizontal, with a minimum to no slope. ÖÖ The structure have to be arranged so that water splashes and mixes as much as possible when entering the pond.

Fish-bone  pattern

Figure 73. Bottom drain.

Normal water  level

Monk with  screen in place

ÖÖ The structure have to be made to avoid the entry in the undesirable aquatic animal or fish in the pond. Crest of  dike

Harvesting pit  (pente 0.5 %)

Pond bottom  (± no slope) 20 cm Bottom drain  (slope 0.2 %)

10 cm

Drainage  channel

Sloping outlet  pipe

Figure 74. Cross cut of a pond at the bottom drain.

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3. PONDS Bottom of the water  supply channel

Inlet

Bottom of inlet 10 cm above  maximum water level Shallow end of  the pond

Bottom of the inlet at the  same level as bottom of  the water supply channel

Figure 75. Cross cut of the inlet of a pond.

VIII.1.1. PIPE INLETS

Pipe inlets can be made from various materials, depending on the water supply required and the inside diameter of the pipe (Figure 76 opposite). Usually, pipe inlets extend for about 60 to 100 cm beyond the edge of the water surface of the pond when it is full, and they should be at least 10 cm above the final water level. One will mainly use PVC pipe or plastic, which are resistant and do not deteriorate easily. In the cases where they are not available, bamboo can be used. Bamboo pipesmake cheap and good inlets whenever locally available (Figure 77 opposite). They can be used in several ways for filling small ponds, for example: 99 Without modification, the water flow being regulated upstream; 99 With the inclusion of a mobile plate for flow regulation; 99 With modification for improving water quality.

Figure 76. Pipe inlet.

Oblique  cut

Flow Metal plate to  open and  close pipe Flow

VIII.1.2. GUTER INLETS

Gutter inlets usually extend for about 1 m over the water surface when the pond is full (Figure 78, p. 92). They can be made simply from various materials such as (Figure 79, p. 92): 99 Bamboo: by cutting a bamboo culm lengthwise in half and cleaning out the partition walls. The diameter is usually limited to 10 cm or less;

Pipe blocked  at end

Figure 77. End of bamboo pipe.

99 Wood: by assembling three boards to form a rectangular gutter. A flow-regulating gate can easily be added; 99 Metal: by bending lengthwise a galvanized iron sheet into a semi-circular gutter. The flow should be regulated upstream.

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Split bamboo gutter 

Wooden gutter

Board water  control

Figure 78. Gutter inlet. About 1m

Corrugated  metal gutter 

Corrugated  metal gutter  Figure 79. Different types of gutter.

VIII.1.3. CANAL INLETS

A small open canal can be built to connect the water supply channel to the pond (Figure 80 opposite). There are several possibilities such as: 99 Digging a small earthen canal, with a trapezoidal section; 99 Building a small lined canal, with a rectangular section and using either wood, bricks or concrete blocks. Small parallel walls are built on a light foundation along the sides of the canal. If necessary, two pairs of grooves are added to regulate the water flow with thin boards and to keep unwanted fish out with a sliding screen.

Figure 80. Canal inlet.

VIII.1.4. SOME ADDITIONAL POINTS ■■ THE OXYGENATION OF WATER

One can rather simply increase oxygen in water at the inlet of a pond when water falls in the pond. The principle is to increase the surface of contact between the air and water. The mixture of atmospheric oxygen to water improves as: 99 The drop height of water increases, 99 The width of the water and the surface of contact with the air increases, 99 The lapping and the fragmentation of water in fine droplets increase. If water feeds the pond through a pipe, one can improve oxygenation: 99 By adding an elbow of 90º at the end of the pipe, opening upwards; 99 While placing a vertical filter perforated on the reversed end of the pipe; 99 By fixing a horizontal perforated screen so that it curves around the end of the pipe and exceeds it slightly. If the feed water falls vertically in the pond via a device in overhang, one will be able to improve oxygenation by putting under the jet a horizontal, plane or undulated panel, which will break the jet.

■■ THE LIMITATION OF THE EROSION OF THE POND

It is essential to position under the water arrival, blocks of stones which will avoid growing hollow in this place of the pond.

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3. PONDS VIII.1.5. THE FILTRATION

At the inlet, filtering devices of water are usually used: 99 To improve water quality by reducing turbidity and while allowing to eliminate certain organic matters in suspension, such as vegetable debris. 99 To limit the wild fish introduction, which can take food, transmit infections and diseases and reduce the production of the ponds. The carnivorous species can destroy the fish stock, in particular smaller ones. It is possible to make various types of more or less effective structures and more or less heavy to implement. Initially, one can put a rather coarse stopping like a grid, on the level of the general water supply channel or the pond to prevent the large debris to pass into the ponds. For the aquatic animals, one will use finer structures. Often, simple net, sometimes mosquito net, were used on the inlet (Photo G below). However, either these grids are filled very quickly and thus require a daily cleaning, or they are destroyed because not solid enough. One can indeed set up more elaborate structures, but which often require higher overcosts. However, it is possible to set up a system simple, not too expensive and requiring a regular but nonconstraining maintenance, may be only one to twice a year, if water is rather clear. It is a question of making pass the water by gravels, then by sand filter (Figure 81 and Photo H, p. 93).

Photo G. Example of non efficient screen at the inlet of a pond (Liberia) [© Y. Fermon].

If the feed water is too turbide and charged in sediment, it is possible to set up a filter decantation before its arrival in the pond,. The principle is simple. It is enough to install a small

Photo H. Example of filters set at the inlet of a pond in Liberia [© Y. Fermon]. Filtering mass Gravel Sand

To fill with  the filtering masses Wire netting Debris Water supply  channel

Concrete Water

Pond

Wild fishes

Dikes

Figure 81. Diagram of an example of sand filter.

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basin upstream and to make water pass there to low flow. The particles will settle to the bottom of the basin which will have to be emptied with saturation. The water which will arrive at the pond will be then clear. This will be later on explained.

VIII.2.

POND OUTLET STRUCTURES

A fishpond of built well must be able to be emptied completely through an outlet device adapted to the dimensions of the pond. Before starting the construction of the dikes themselves, it is necessary to envisage the installation of an outlet device. Preferably, one will install the system of draining at the same time as the construction of the dikes, by leaving the necessary space, or before the dikes. Two main reasons justify the construction of outlet structures: ÖÖ To keep the water surface in the pond at its optimum level, which usually coincides with the maximum water level designed for the pond; ÖÖ To allow for the complete draining of the pond and harvesting of the fish whenever necessary. ÖÖ ÖÖ ÖÖ ÖÖ ÖÖ ÖÖ ÖÖ

In addition to these major functions, a good outlet should also ensure as far as possible that: The amount of time necessary to drain the pond completely is reasonable; The flow of the draining water is as uniform as possible to avoid disturbing the fish excessively; There is no loss of fish, especially during the draining period; Water can be drained from the top, bottom or intermediate levels of the pond; Any reasonable excess of water is carried away; The outlet can be easily cleaned and serviced; The construction cost and maintenance are relatively low. In most cases, outlets have three main elements:

99 A collecting area on the inside of the pond, from which the water drains and into which the stock is collected for harvest; 99 The water control itself, including any drain plugs, valves, control boards, screens and gates; 99 A means for getting the water to the outside of the pond such as a pipe or a cut through the wall, and/or an overflow structure. In both cases, a protected area on the outside of the wall must prevent the drain water from scouring the walls or drainage channel. Pond outlets can be built in various ways, using different materials such as bamboo, wood, bricks, cement blocks or concrete. There are four main types: 99 Simple cuts through the dike; 99 Simple pipelines and siphons; 99 Sluices dikes; 99 Monks. In several handbooks, one recommends that a simple pipe is enough: it can be in bamboo, PVC, wood, iron or concrete and of a diameter of at least 100 mm for the small ponds from 3 to 5 ares. The interior diameter of draining will determine the capacity of flow of the structure. However, in practice, it appears that above 100 m2 (or 1 are), the monk is most reliable and allows a good management of the water of the ponds. For the lower ponds (storage, stocking with fish), one will be able to use pipes. So only the two preferential methods of draining will be shown here.

VIII.2.1. PIPE OUTLETS

One will choose the size and the quality of the pipes which it is advisable to use according to the surface of the pond and the necessary diameters. Diameters from 5 to 10 cm is enough for ponds to size lower than 100 m2. The pipes can be in bamboo, galvanized metal or plastic (PVC). An outlet can be a straight of low diameter. It is important that the pipes used for this purpose are installed at the lowest point of the pond, before the dike is not built. The method with a pipe which is the best to control the height of water is that to use a turn-down stand-pipe.

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Subsistence fishfarming in Africa

3. PONDS This pond outlet is made of three rigid plastic parts: 99A slightly sloping base pipeline, made for example of one or more PVC pipes running through the dike, 99A vertical pipe, which reaches up to the maximum water level;

Steel post Pipe with screen at  water level

Attach pipe to  steel post

9A 9 90°-elbow, which connects these two pipes. It can be glued to the vertical pipe with plastic cement, but need not be unless the fit is very loose. The connection to the base pipe is unglued, but can be greased with a suitable material such as mineral grease, lard or palm soap. This type of outlet can be set up either inside the pond, in front of the dike or outside the pond, at the back of the dike, in which case you need a screen at the inner end of the base pipe. It is usually best to have the vertical pipe inside the pond to reduce the risk of blocking the horizontal pipe and to control leakage (Figure 82 below). If possible, design the opening of the horizontal pipe to be at least 10 cm below the lowest point in the pond. One can carefully fix the vertical pipe at the steel stake located in front with a rope or a chain, which avoid accidental movements. One will place at the end of the vertical pipe a narrowly adjusted netting.

Wooden  board

10 cm Concrete anchor will  hold pipe firm 90° elbow Unglued

To regulate the water level in the pond, it is just enough to set the pipe at the required angle by turning it up or down. Then, one have just to fix it in the set position with the chain or rope.

Maximum water level

Maximum water level

Partially empty

Completely  empty

Lower pipe to  empty pond

Water level Protection  of the pipe

Drainage of the water Downstream dike

Downstream dike

Drain pipe

Drain pipe

Figure 82. Turn-down pipe inside pond outlet.

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To drain the pond, one will turn the vertical pipe down progressively, following the water level as it drops. When it has reached the horizontal position, one will just remove the elbow pipe from the end of the horizontal pipe to end the draining of the pond and harvest the fish. It is possible to use this system for handling normal overflow water, because any surplus in the pond above the selected pipe level will automatically drain.

VIII.2.2. THE MONK OUTLET

The monk is one of the oldest and most common pond draining structures. The monk is a U-shaped pipe towards the interior of the pond, and prolonged at his base by a drain. Water is evacuated by this drain under the dike. The structure is built at the deepest point of the pond. The monk includes two side and a back. Two or three parallel grooves arranged vertically on each side can receive small boards of wood which, by juxtaposing each other, closes the monk on the open side towards the interior of the pond. Space between the first two lines of small boards is stuffed with clay, to make this part watertight. In the third possible pair of grooves, grids replaced small board and prevent the escape of fish during drainings. This third pair of grooves is very useful in practice especially at the end of the draining. Indeed, when one reaches the last water fringe at the bottom of the pond, the capture of fish accumulated in front of the opening of the monk always does not leave time as well as possible to manage the first two pairs of small boards, and the presence of the grids in the third consequently appears salutary. The pond water level is easily controlled and adjusted. It can function as an overflow. It simplifies the fish harvest. In addition, a monk is more easily to use, and it is more economical to build if the pond dike is large. However, it has the disadvantage of not being very simple to construct, particularly if it is built with bricks or concrete. The complete monk outlet consists of (Figure 83 below): 99 A vertical three-sided tower (called the monk), usually as high as the outlet dike; 99 A pipeline running through the dike, which is sealed to the back of the tower at its base; 99 A foundation for the tower and the pipeline; and 99 Grooves to fix the wooden boards and screens which form the fourth side of the monk. Similar to any other outlet, the monk is generally built on the side of the pond opposite the water inlet. It may be placed either in the middle of the dike or, when the water drains, for example, in a catch basin common to two adjacent ponds, in a corner of the dike (Figure 84, p. 97). The foundation of the monk is built by taking account of the later pressure of water on the structure, and especially of the levels to respect to ensure the gravitating draining of the pond. In any case, the base of the monk in front of the draining pipe will have to be slightly in lower part of the lowest point of the plate of the pond, and of course, higher than the maximum level of the bed of the river of drainage. Grooves

Pipeline

Wire netting

Clay Drainage of the water Wooden plates

Verticale  tower

Foundation

Figure 83. Composition of a monk.

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3. PONDS The monk can be built either into the dike or freestanding some distance into the pond (Figure 85 below): ÖÖ If the monk is built into the dike, water infiltration through the dike will be more common and access to the outlet will be easier for poachers. To prevent soil from entering the monk, you will have to build an additional protective wing on both sides, but servicing the monk will be easier; ÖÖ If the monk is built on the pond bottom in front of the inside toe of the dike, you will need a longer pipeline, but access to the monk will be through a removable catwalk and tampering with it will be much more difficult.

Water supply channel

Monk in  the middle

Monk in a  corner

Drainage channel

Figure 84. Position of the monk in the pond.

Monks can be built in wood, bricks or concrete depending mainly on the availability of materials, their cost, the local technical expertise and the size of the structure. The most difficult type of monk to build is the brick monk. It requires a very skilled mason to make it so that it is leak-proof. If not done properly, the mortar surfacing will have to be redone frequently, increasing maintenance costs. Generally, wooden and concrete monks are cheaper and easier to build. The following are some points to remember when one build a monk: ÖÖ The pipeline should be laid down before building the dike and the monk tower. ÖÖ A solid foundation have to be built to avoid future problems. ÖÖ A particular attention have to be paid to the junction of the monk tower to its foundation; the junction of the pipeline to the back of the monk tower; the finishing of the monk’s grooves. ÖÖ A reasonable slope to the pipeline have to be made, preferably 1.5 to 2 percent. ÖÖ If several monks have to be build on the fish farm, one have to try to standardize their type and size as much as possible; and, for concrete monks, one need to prepare strong forms and re-use them if possible. ÖÖ One have to provide a separate overflow wherever there is danger of uncontrolled entry of flood water into the pond.

Top of the  dike

Top of the  dike

Monk

Monk Dike

A

Outlet

Outlet Dike

B

Figure 85. Position of the monk according the downstream dike. A: Integrated in the dike; B: Inside the pond.

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■■ WOODEN MONK OUTLETS

A simple monk outlet can be built entirely of wood. It is the easiest and cheapest type of monk to construct, although you need to be careful to ensure its watertightness and its durability. The height of a wooden monk should be limited to 2 m (Figure 86 below).

3 x 5 cm  cross-support

5 x 5 cm posts

5 x 5 cm posts

Inside  dimensions ≈ 20 x 22 cm

Inside  dimensions  ≈ 28 x 46 cm 100 à 120 cm 150 cm

Oblique  brace Pipeline

Pipeline 50 cm

27 cm

50 cm

30 cm

A

B Figure 86. Wooden monk. Small (A) and medium (B) size.

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3. PONDS To build a monk out of wooden, it is necessary to choose a heavy and durable wood, resistant to water. The durability of wood can be improved by application of a discarded engine oil or preservative. One should not however forget to wash wood before putting the fish in the pond. It is necessary to use small planks without knots, from 3 to 5 cm thickness. Thus, one will need approximately 0.4 m3 of wood for a 2 m height monk. In the majority of the cases, it is not necessary to envisage foundations as they are very light, although in the presence of less stable grounds it Figure 87. Wooden pipe. can be indicated to envisage simple piles of wooden for foundation. Usually, it is sufficient to build them on light foundations, for example flagstones of paving or simple wood piles or rather broad boards posed flat on the bottom of the pond. Both the small- and the medium-size monks are composed of boards nailed or screwed together, so that the face turned towards the pond is open. It is preferable to screw a post of anchoring on each side of the column. It is necessary first of all to insert these two posts until a sufficient depth in the bottom of the pond, then to screw them with the monk. If one wants to improve solidity of the work, it is possible to add an oblique brace to each side, supporting the upper part of the column against the drain. Instead of using standard elements of concrete or plastic drain, one can entirely build a drain in wood (Figure 87 above). It is enough for this purpose assembling by nails or screws four boards assembled out of rectangular box. One carefully fixes the drain thus carried out on a well compacted soil and one hides it under the dike.

■■ SMALL BRICK, CONCRETE BLOCK AND CONCRETE MONK OUTLETS

Monks of up to 1.5 m in height, fixed to pipelines up to 25 to 30 cm in diameter, can be built using single- thickness brick and mortar. Although taller and wider monks can be built, they require a double-width base and good bracing for stability and strength, and so become too heavy and expensive for most purposes. The rules of construction to be observed for small monks are: ÖÖ The monks in bricks and breeze blocks must have interior surfaces carefully finished, covered of a coating. This technique revealed three major problems: 1. The breeze blocks are hollow and rough-casting is exhausted quickly. Escapes, not easily reparable, appear on the growing old monks. 2. The monk is often unnecessarily tall within sight of the flow which the pipe can evacuate (what requires of the rather long and relatively expensive boards to close the monk). 3. It is impossible to carry out two of the same width monks being able to use the same grids or the same boards. On the other hand, this construction is not expensive. ÖÖ For concrete structures, it is necessary to request the services of a qualified mason. The quality of execution must indeed be excellent to guarantee the durability of the work. At the beginning, the construction of the formwork was done on site. Construction on site of formwork made it possible to make the concrete which took the shape of a monk to the release from the mould. This technique presented a difficulty at the time of its implementation. The construction of the mould on the spot proved to be delicate, the sometimes hazardous dismantling and the problematic recovery of the boards. What increased much the cost of construction. The monks were generally of different sizes but much more solid. Since one uses a better solution: the dismountable and reusable mould (Figure 88 and Photo I, p. 100). The idea was to design a reusable dismountable mould. Moreover, this solution guarantees a standard dimensioning. However, the first moulds were rather heavy to transport. When the fishfar-

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99

Clamp

A

B Figure 88. Mould of a monk. A: Front view; B: Upper view.

mer invested itself in the research of sand and the gravel, these monks were finally less expensive than those which are carried out in breeze blocks. Then, this type of formwork undergoes major changes. As private individuals again, the mould is from now transportable by only one person with foot or bicycle. The shuttering timber coats oil internally (engines oil of vehicles for example) is thus carried out above the foundation in order to run the wings and the back of the monk. As an indication, the dimensions presented in Table XVII below can be adopted, according to the size of the pond. Thus, for a pond from 0.5 to 2 ha, the formwork to be run will be able to have: 2 m Table XVII. Informations on the dimensions of the monk according the size of the pond. Surface of the pond

S < 0.5 ha

S > 0.5 ha

Height (m)

1.50

2.0,

Bach width (mi)

0.54

0.70

Sides width (m)

0.44

0.54

Depth of concrete

0.12

0.15

Photo I. Mould and monks (Guinea). On left: The first floor and the mould; On right: Setting of the secund floor [© APDRA-F] (CIRAD).

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3. PONDS Table XVIII. Estimation of the discharge and draining duration of the pond according the diameter of the outlet. Diameter (cm)

Discharge (l/s-1)

Discharge (m3/h-1)

Time for the drain of a pond of 4 ares (Mean depth: 1 m)

10

8

28.8

13 h 53

15

18

64.8

6 h 11

20

31

111.6

3 h 35

30

70

252

1 h 35

40

130

468

52 mn

from height, 0.7 m of width of the back, 0.54 m for the wings and 0.15 thickness. The mixture of the concrete to be used will be of 1 volume of cement for 2 volumes of fine sand and 4 volumes of gravel, for the monk described, 4 cement bags, 4 sand wheelbarrows and 8 crushed stone wheelbarrows. The capacity of flow of a monk is related to the internal diameter of the drain. The cross section of the monk increases according to the diameter of the drain (Table XVIII above, Table XIX and Figure 89 below). The following points are important: ÖÖ The interior width of the column must be equal to the diameter of the drain increased from 5 to 10 cm on each side; ÖÖ There must be a space from at least 8 to 10 cm in front of the first groove; ÖÖ The two series of small boards must be separated by an interval from at least 8 to 10 cm; ÖÖ The distance between the last series of small boards and the back face of the column must be all the more large as the capacity of flow is high, without however exceeding a maximum value from 35 to 40 cm To facilitate the operation of the small boards, it is preferable to limit the interior width of a monk to a maximum value of 50 cm. D 5 to 10 cm

5 to 10 cm

Table XIX. Inside dimensions of the monk according the diameter of the pipe. Pipeline inside diameter (cm)

3 L

10-15

15-20

20-25

25-30

r

Internal width

30

33-35

40

48-50

r

In front of groove 1

8

10

10

10

Gap between grooves 1 and 2

8

10

10

10

Distance between groove 2 to wall

16

16-20

26

34-37

Width for two grooves

8

8

8

8

Internal length

40

44-48

54

62-65

2 1 W W = Width  D = Diametre of the pipe L = Lenght r = Grooves W = D + 2x (5 to 10 cm) L = (1) + (2) + (3) + r + r (1) = 8 to 10 cm (2) = 8 to 10 cm (3) = maximum 35 to 40 cm r = 4 cm each

Figure 89. Monk. Upper view and example of size.

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101

Photo J. First floor of the monk associated with the pipe (Guinea) [© APDRA-F](CIRAD).

Clay

Photo K. Top of a monk (DRC) [© Y. Fermon].

Figure 90. Functioning of a monk.

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The maintenance of the mould requires a minimum of attention. It is preferable to store it made so that it becomes not deformed and to coat it as soon as possible with engine oil. Used well, a mould can make more than 20 monks. By leaving some iron stems in the still fresh concrete to make the junction with the following stage, it was completely possible to build by stage a monk of more than 2 m (Photo I, p. 100 and Photo J above). The soil used between the small planks to block the monk must be rich in organic matter in order to keep its plasticity. Too pure clays often fissure side of the tube, which is not long in causing escapes. The height of water in the pond is thus regulated by the monk thanks to the small boards out of wooden between which one packs clay (Figure 90 opposite). Water is retained in the pond by this impermeable layer up to the level of the highest small board. Netting at the top of the last small board prevents fish from leaving the pond over the highest

3. PONDS Build wooden  form using  2 cm boards

Top cover

Chip a notch in the foundation  to secure side walls

A Foundation

B

C

Figure 91. Concrete pipe. A: Croos cut; B: Mould; C: Final pipe.

Photo L. Building of a pipe (Guinea) [© APDRA-F](CIRAD).

small board of the monk. One will always take care that the meshs of netting are smaller than fish raised in the pond. When the pond is filled to the last small board, all the water which enters more in the pond, crosses the grid above the impermeable layer and falls to the bottom of the monk. In this place, it crosses the dike then leaves the pond while passing by the drain (Photo K, p. 102). The monk ended, it is essential to equip it with foundations called soles. The sole is also used as plane surface and hard to catch last fish easily. The monks of this type are generally provided with drains. One can use a PVC drain or set up concrete tubes. If one wants to obtain the best results, the drain must have a good foundation whose construction must be done at the same time as that of the column of the monk (Figure 91 and Photo L above). The seals of the drains must be carefully sealed to avoid the water escapes. In the wet environments, because of water abundance which compensates the risks of escape, the concrete tubes constitute a good technique: ÖÖ They are cheap: two baggs of cements are enough for 10 m of tube for which it is necessary to add a half bagg for the seals; ÖÖ Their section allows an higher capacity that of a pipe of 100 or 120 mms in diameter; ÖÖ The flat bottom of the tube makes it possible to accelerate the ends of draining, which is very practical; ÖÖ It is easy to add a tube when the need is felt some. However the concrete tubes present also some disadvantages, in particular in the dry zones, which are as many recommendations: ÖÖ The mould must be quite manufactured and correctly maintained so that the junctions are encasable and remain it; ÖÖ It is preferable to assemble the tubes before building the dike, it is thus easier to move the water. One can then install them on a dry and hard soil instead of posing them on mud;

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ÖÖ It should be taken care that the tubes are well buried under the slope so that when the fishfarmer goes down to this place to visit his monk, it does not loosen the covers of the tubes; ÖÖ Along the tubes (as along the pipes) a zone of weakness constitutes around which it is carefully necessary to ram, if not risks of infiltrations is important.

VIII.2.3. ADDITIONNAL STRUCTURE OF OVERFLOW

For safety reasons, one will have to always prevent that the water level in the pond exceeds the maximum level and that water flows over an unspecified dike. Any water in excess which penetrates in a pond already filled - water of flood or of streaming, for example - must be immediately and automatically evacuated. Such an incident would cause the loss of most of the fish stock and would require also important repairs before starting again the exploitation of the pond. In the case of a diversion pond, of which most of overfow is diverted at the diversion structure, a draining device such as an open vertical pipe or a monk must evacuate any overflow automatically. It should however be taken care that all the grids are maintained in good state of cleanliness. A monk also provides the function of overflow. One can however add an additional pipe to mitigate the filling of the grid for lack of attention. During heavy rains, the amount of surface runoff may become excessive, particularly for barrage ponds or ponds built at the bottom of large sloping areas with little vegetation cover. The runoff water in such cases is also often heavily loaded with fine soil particles that make it very turbid. If the runoff passes across cultivated areas it might accumulate toxic substances such as pesticides. To avoid such water reaching your fish farm, you will have to protect it with one or more protection canals If the pond is deprived of emptying device to free flow or if this device is too small, and if the quantity of water in excess is always limited, it is possible to install a pipe of overflow which can be in bamboo, PVC or galvanized iron (Figure 92 below). It is best to use one-piece pipes, avoiding any joints. If the pipe sags, or extends too far out from the outer side of the dike, it may be useful to put up some simple pipe supports, using for example wood or bamboo.

Protecting  outside of dike  with stones

Protecting outside of  dike with a  corrugated metal  channel

Supporting a  long pipe

Maximum water level

Angle the pipe so that  inside opening is 15  to 20 cm below  maximum water level Place overfow at  corner of pond

Figure 92. Setting of a pipe overflow.

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Maximum water level

Remove deeper water  by curving down inside  end of pipe

3. PONDS VIII.3.

SEDIMENTATION TANK

A sedimentation tank (or setting basin) is specifically designed to improve water quality by removing the mineral soil particles, such as fine sand and silt, which can be present in great quantities in certain waters with a high turbidity. This is achieved by reducing the water velocity sufficiently to allow the particles to settle. There are different types of settling basins (Figure 93 below): 99 A simple small pond, built at the beginning of the water supply channel;

99 A rectangular basin built on the feeder canal with bricks, cement blocks or concrete (Figure 94, p. 106). If the settling basin is a simple rectangular basin, the size will be determine as follows: ¾¾ Its minimum horizontal area. For example, for a flow of 0.030 m3.s-1 and to settle a particle which has a diameter greater than or equal 0.1 mm, Therefore the minimum horizontal area of the settling basin will be of 5.6 m2. in these ideal conditions, 100 % of particles of 0.1 mm or larger should settle. A smaller proportion of smaller particles will also settle. The smaller the particles, the less the percentage settling. ¾¾ The minimum cross-section area . It will be of 0.3 m2, in the following example. ¾¾ The minimum width. In the following example, it will be of 1.2 m. ¾¾ The standard length. It will be of 4.6 m in the example. ¾¾ The depth, which is the sum of the water depth (0.25 m), the freeboard (0.20 m) and the setting depth (from 0.10 to 0.20 m). In the example, it should be of 0.60 m. The settling basin can be wider, with a larger cross-section. This will then allow the standard length to be shorter. As long as the critical velocities are not exceeded, the basin can be shaped to fit local space and to minimize construction costs. As a general guide, ratios of length: width are typically between 2:1 and 5:1. The bottom of the settling basin is built lower than the bottom of the water feeder canal, to concentrate the soil particles being removed from the incoming water. The above design can be improved in the following ways: ÖÖ At the entrance, make the water pass over a wide edge near the basin’s surface, similar to a weir, to minimize disturbances. ÖÖ At the exit, similarly make the water spread over a wide edge near the basin’s surface. ÖÖ Avoid cross-wind exposure as this can often agitate the water and resuspend particles. ÖÖ Within the basin, add some baffles to slow down the water further and make it follow a longer zig-zag path. With these baffles, you can reduce the basin’s length by one third.

 3 m - 10 m

 1 m x 7 m

Sand and  silt

Sand and silt

A

B Figure 93. Type of setting basin. A: Natural; B: In concrete. Subsistence fishfarming in Africa

105

0

1 m

0

Section

A

1 m

Section

B 2 %

Figure 94. Setting basin. A: Normal; B: Improved.

Plan

ÖÖ Make sure water flows evenly and quietly through the settling basin. Avoid creating areas of turbulence or rapid flow. ÖÖ Provide a sloping bottom (slope = 2 percent) from the downstream end to the entrance of the basin. The settling basin have to be regularly clean by removing the accumulated soil from its bottom after closing the water supply. This soil have to be removed more regularly using a simple pipe or siphon. Usually, the soil is very fertile, and can be use it in the garden and fields to make the crops grow better.

IX. ADDITIONAL INSTALLATIONS IX.1. THE ANTI-EROSIVE PROTECTION

Once the pond dug and the various works in place, the dikes must be protected from erosion, by sowing grasses crawling on the upper part, at the top, on the dry side and the wet side up to the normal level of water (freeboard) in the pond. For that, one can spread out a layer from 10 to 15 cm of topsoil over the zone to be turfed (Figure 95 below). This ground is obtained either from the topsoil stock previously extracted with the site pond, or in the vicinity. One will plant the cuttings or the turfs with relatively brought closer intervals. Then, one will sprinkle immediately after having planted and, thereafter, with regular intervals. As soon as the grass is established, it should be cut short regularly to stimulate its extension to all surface. In the event of strong rains, one can use a temporary protective system, for example hay or other materials, as a long time as herbaceous cover is not complete. One can use the space of the dikes (Figure 96, p. 107). In certain areas, pot cultures or fodder plants can grow (A) there, but it is necessary to take care to choose species ensuring a good cover of the ground and of which the roots are not likely to weaken the dikes too deeply by penetrating the ground or by altering its structure. Only of small animals can graze or circulate above (B). One should not plant trees on the surface or near the dikes, because the roots would weaken them (C).

10 to 15 cm of steppe  black soil

Plant grass

Seed

Figure 95. Setting of a vegetable cover on the dikes.

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3. PONDS

A

B

C

Figure 96. Dikes with plants. A: Vegetable garden; B: Small animals; C: Trees.

IX.2. THE ANTI-EROSIVE FIGHT

At the time of the installation of the ponds, it is particularly important to make sure of the risks of erosion of the catchment area. The erosion of the ground has negative effects on water quality and on the fishfarming installation itself. When water runs out on a slope, it involves with it particles coming from the ground of surface. More the flow is important and fast, more there are carried particles. Erosion can involve: ÖÖ Serious degradations of the slope itself and properties of the ground, which reduces the fertility; ÖÖ An arrival of turbide water in bottom of the slope and problems of deposits of ground elsewhere. It will be necessary to try to control as much as possible the erosion of the grounds on the slopes to prevent that turbide water does not go in the ponds (Figure 97 below). This practice, called conservation of the grounds, can generate significant advantages: ÖÖ Richer soil on the slopes and a greater production of various products such as wood, fruits, fodder or food; ÖÖ A better water quality in the ponds and a more important production of fish. The vegetation protects the ground against erosion. The roots contribute to stabilize the particles of ground and to increase the permeability of the sub-bases. The organic matters which it brings in the ground, like the humus, increase resistance to erosion and slow down the streaming. It can also contribute to the deposit of the particles of ground. By arranging the natural vegetation on the slope grounds, it is possible to guarantee that the ground acquires a greater resistance to erosion. In the zones covered with forests, it is necessary to completely maintain the cover of the ground as possible by managing the exploitation of the trees and by protecting the forest against the excessive pasture and fires. The forests having a good low vegetation, well disseminated radicular systems and a good cover by the leaves offer the best conditions. In the zones of savanna, one will control the use of fire for the regeneration of the grazing grounds and will give the preference to early fires to guarantee sufficient new growths before the beginning of the rains. It will be necessary to avoid the excessive pasture, in particular by the sheep and the goats. As soon as possible, it is necessary to envisage rotations for the pastures. If one is not able to fight against erosion, one can have recourse to a channel of protection to collect and divert water turbides or, if necessary, to improve water quality of food by using a setting basin (paragraphe VIII.3, p. 105).

Pond

A

g

Streamin

Pond

B

Pond Infiltration

C

Protection channel

Figure 97. Type of erosion and soil conservation. A: Streaming; B: Infiltration; C: Protection channel.

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107

IX.3. BIOLOGICAL PLASTIC

If the ground used can let infiltrate water, it will be necessary to use the technique of “biological plastic”, to reinforce the sealing of the plate of the pond. This technique allows to reduce the water leaks and infiltrations by filling the plate and the dikes of a pond built on a ground not impermeable enough. The realization of the biological plastic is done in the following way: 1.

After having regularized the structures well by removing vegetable debris and stones, one covers all the plate and the future water side of the dikes with waste of pigsty.

2.

One recovers then this waste using leaves of banana tree, straw or other vegetable matters.

3.

Then, one spreads out a layer of ground over the unit and one rams copiously.

4.

Two to three weeks after, the pond can be fill with water.

IX.4. THE FENCE

The fence prevents the entry of predatory of all species (snakes, frogs, otters…) in the enclosure of the pond (Figure 98 and Photo M below). It can be made of a netting, that one buries on at least a 10 cm depth and the higher end turned towards the pond. Metal stakes or of not very putrescible wood are thus established all the 50 - 90 cm to be used as support with the grid fixed using wire of fastener. For the bamboos, it will be necessary to think of their replacements after 18 months to the maximum in tropical zone. Other materials other than netting can be used. In all the cases, it is advisable to take care that the fence does not have any hole on the whole of its perimeter. The second role is also to limit the poaching which is one of the important causes of the abandonment of the ponds. The use of the access doors in the enclosure of the ponds will have to be, so controlled well. If necessary, if the piscivorous birds are too numerous, one can have recourse to the installation of a coarse net on the ponds and to the use of scarecrows.

Photo M. Setting of a fences with branches (Liberia) [© Y. Fermon]. Stream

Pond Fishponds Fisherman

B

Door

Predators Thief

Dikes

Channel

Controle of water level

Figure 98. Fences (A). In scrubs (B); In wood or bamboo (C).

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A C

3. PONDS IX.5. THE FILLING OF THE POND AND TESTS

As soon as possible and before the completion of the pond, it is advisable to put it under water:

ÖÖ To check that all structures function properly such as the water intake, the canals, the pond inlet and outlet; ÖÖ To check that the new dikes are strong and impervious enough; ÖÖ To accelerate the stabilization of these dikes. For maximum security and efficiency, one willproceed in the following way: 1.

Fill the pond with water very slowly and up to a maximum depth of 0.40 m at the outlet.

2.

Close the water supply and keep water in the pond for a few days. During this period, check the dikes carefully. Repair crevices and collapsed sections, compacting well.

3.

Drain the water completely and leave the pond dry for a few days. Keep checking the dikes and repair them as necessary.

4.

Fill the pond again very slowly and up to a maximum level about 0.40 m higher than the previous time.

5.

Close the water supply. Check the dikes and repair them as necessary. After a few days, drain the pond completely.

6.

Repeat this process of filling/drying until the water level in the pond reaches the designed maximum level.

7.

Check and repair the dikes as necessary.

X. NECESSARY RESOURCES X.1. MATERIALS

The initial stage of prospection and the picketing of the site requires only few material. It is about: 99 Stakes 99 Tie up and ropes 99 Decametre 99 Machete 99 Two-handed hammer 99 Plumb level or if possible, a theodolite or automatic level 99 Paper and pencils

Then, it is necessary to make the list of the technical descriptions, while referring in the topographic plans and the drawings of detail available. These descriptions must separately treat earthworks and works, as indicated hereafter: 1. Descriptions of the earthworks: (i) Preparing the ground of the site, in particular clearing and uprooting complete, handling and placement of the cleared vegetation; (ii) Removal of the layer of topsoil, with indication of its surface, its thickness and places of storage; (iii) Construction of the dikes, with indication of the source and the quality of the ground as well as its characteristics; (iv) Compaction of the dikes, with mention of the maximum thickness of the layers, the moisture of the ground, the capacity and the type of equipment to be used 2. Descriptions of the structures, indexing the types and characteristic of materials to be used in each case, such as: (i) Reinforced concrete - type of proportioning, limits to be observed during the test of depression, types of reinforcements, method of cure, formwork; (ii) Wood - detailed list of the species, treatment, relative humidity, conditions of storage;

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(iii) Bricks or breeze blocks - quality, finished external, standard, weight, conditions of storage; (iv) Pipes - type, material, storage, handling, pose; (v) Mortars and coatings, additives, water…; (vi) Paintings - indication of the number of layers, the type of painting. For the building work carried out with the hand, simple tools are necessary: Hoe, shovel, machete, pickaxe, wheelbarrow and/or basket, matchet, buckets, axe, bar with mine, dig, roller of wire, plumb level, ram, hammer, two-handed hammers, decametre, saw, screw clamp; In materials used and consumable: 99 Planks of wood, 99 Pipe PVC or out of galvanized iron, 99 Concrete, 99 Sand, 99 Gravel, 99 Concrete-reinforcing steel 99 Stakes, 99 Sheets of banana tree, 99 Oil of draining, 99 Painting. In most of the cases, the needs for inputs will be only the pipe PVC and the concrete. It happens that the concrete is not easily available. One will be able to then choose to make local brick or wood structures improved in order to support the immersion. Time between two repairs is then likely to be reduced, the concrete monks which can last more than 20 years.

X.2. HUMAN RESOURCES AND NECESSARY TIME

Work can be made by the beneficairies and the members of their family, with the assistance of some friends if necessary. It is possible also, to accelerate the time of construction, to sign a contract with daily workers to dig the pond by hand for a fixed price based on the volume of the earthworks. Each pond generally does not have more than 400 m2 of surface. The volume of the earthworks makes it possible to estimate time that each pond will be needed and, if necessary, to build the price to envisage to sub-contract this task. Table XX. Examples of necessary time for building of ponds (man/day). 1 pond of 400 m2

2 ponds of 200 m2

130

266

130

50 (200 m)

50 (200 m)

70 (270 m)

600 (150 m3)

1600 (400 m3)

3600 (950 m3)

Main water supply Water supply channel Excavation/construction of the dikes Inlet/Oulet Total Time

4 of 400 m2 and 2 of 100 m2

5

4

90

785

1920

3890

Table XXI. Approximate output on the works of excavation made by hand. Volume excavated (m3/j) Nature of the soil

With hoe

With pickaxe / shovel

Soft (deposits, sandy soil)

2.5 – 3.0

3.5 – 4.0

Moderately hard (silt, light clay)

1.5 – 2.0

2.5 – 3.0

Hard (heavier clay)

1.0

2.0 – 2.5

Lateritic, moderately hard

0.5

1.0 – 1.5

0.8 – 1.5

1.5 – 2.0

Water saturated

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Subsistence fishfarming in Africa

3. PONDS The standards of work relating to the earthworks carried out with the hand will depend mainly on the nature of the ground. The harder it is to work and the less high the outputs are. The presence of water in excess results also in to reduce the outputs, in particular in the presence of clays heavy and sticking One will see in Table XX, p. 110 examples of duration for each section of work. Times strongly vary and are given only as an indication. For example, a pond of 200 m2 took 20 days full for 20 people, that is to say a total of 400 men per day (8 work hours manpower per day) in Liberia. In Cameroun, for a complete exploitation of 2 ha with 15 ponds of 400 m2 each one, a eclosery of 10 x 10 m2, an office plus a store of 150 m2, 5 hen houses and 5 pigsties, time was of 226 men per day by pond. This corresponds to a total of 3435 men per day for the whole of the exploitation. Standards of work applicable to the excavation work carried out with the hand are indicated to Table XXI, p. 110. They are the average outputs to the excavation and the throw at a distance from 1 m which one can discount of medium worker who carry out earthworks during eight hours per day: the minimal values correspond to the use of the hoe and the maximum values with the use of the pickaxe and the shovel under similar conditions. These outputs must be slightly reduced when the distance from throw increases. For work of excavation and shaping of the channels, the output of a qualified digger varies from 0.8 to 1.2 m3   day. One can estimate the duration of the work overall, but for each case, one will have to recompute this calendar according to the means available (Table XXII below). If the number of workers is sufficient, several stages can be done in same time. In time, it is desirable that the earthworks are done at the time when the costs of construction will be weakest. The most favourable moment is thus the dry season, especially at the end of the season for the earthwork. At this time, the bearing pressure of the ground is better and the swamps are not saturated of water. For the programming of work, one thus designs a calendar in which the programming of each task will appear (Table XXIII below). Table XXII. Example of calendar of works to do for the construction of a pond (workers of 400 men per day). Activities in dark. For 3 or 4 ponds

Activities/Week

1

2

3

4

5

For 1 or 2 ponds 6

7

8

1

2

3

4

Clear vegetation Remove topsoil Dig supply channel Build main water intake Build the main draining structure Build the outlet Build the inlet Build the dikes Finalising the pond

Table XXIII. Example of calendar according the seasons (15 ponds) in Cameroon. Activity/Month

Sept

Oct

Nov

Dec

Jan

Feb March April

May

June

July

Aug

Sept

Clean the site Topographic plan Design setting Water supply Excavation works Other

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111

One will see in Table XXXVI, p. 169 of the examples of management for 4 ponds for a construction of approximately a month (400 men per day). Cleaning can take less time if the labor is sufficient to ensure several building sites at the same time.

XI. SUMMARY

ÖÖ All of the operations being carried out can be summarized in the following figure:

Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Draining channel Pond bottom drain laying out Purchases of  fishing nets Building of cages  or hapas Duration:  3 to 6 months

Other structures laying out

Completion and filling in water

ÖÖ Emphasis on: ÖÖThe cleaning of the site that must be done well ÖÖThe picketing which must be precise for the slopes ÖÖThe control and management of the water by channels ÖÖThe importance of dykes, their strength and their size and although compacted ÖÖThe choice of a monk for draining ponds ÖÖThe total isolation of the ponds from the outside for better control ÖÖThe soil conservation upstream

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Subsistence fishfarming in Africa

Chapter 08

BIOLOGICAL APPROACH The pond is now in water. So, the biological aspects can start (Figure 100, p. 114). A pond is an environment that will turn on itself. It will need to ensure the start and development of the biological cycles. Following the construction of the pond, the following stages will be: 12.  Fertilization 13.  Waiting for a « green water »

I. THE LIFE IN A POND The pond is a small ecosystem with several trophic levels comprising the micro-organisms and algae, the plankton, the insects and larvae of insects. Then, the fish which are the important component that one wants to make grow in an optimal way (Figure 99 below). Plant photosynthetic organisms are the only living organisms able to transform mineral matter into organic matter. The development of complex molecules requires energy which the plants collect from solar energy. The organic matter is initially produced from minerals by the photosynthetic plants. Thereafter, it can be assimilated and transformed by the animals. The animal organisms consume organic matter to grow, they are unable to develop from minerals. The organic matter (vegetable debris, dejections and dead animals), is decomposed and mineralized and turns by this process to mineral matter. It is estimated that one needs 1 kg of phytoplankton to obtain 10 g of fish like tilapia (Figure 101, p. 115). The population of each trophic level must indeed be definitely higher than that of its predators to be able to renew itself. Green: Producer Black: Consumer  Brown: Decomposer

Sun light

Photosynthesis Assimilation Predation Decomposition

Hydrophytes  aquatic plants

Plankton

Minerals NPK (Nitrogen,  Phosphorus...)

Phytoplankton Algae

Zooplancton Nekton Small  invertebrates

Benthos Bacteria

Figure 99. Schematic life cycle of a pond.

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0

3 months

Assessment Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Duration: 3 months

Selection Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Draining channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas Duration: 6 - 9 months 3 to 6 months

Completion and filling in water

Fish farming Fertilization

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Maintenance and  follow-up of the  ponds

Stocking with tilapia Follow-up  of the fishes

7 - 10 months Duration: 4 to 12 months

Stocking with  predators

End of the cycle 11 - 22 months

Outside composter

Storage of  fishes Duration: 0.5 to 1 month

Draining of the pond  and harvest Sale and\or transformation  of the fish

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Figure 100. Setting of fish pond: 4. Fishfarming.

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Subsistence fishfarming in Africa

Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

4. FISH FARMING Tertiary consumers Super-carnivores

1 g

Secundary consumers Carnivores

10 g

Primary consumers Herbivores

100 g

Primary producers Plants, phytoplankton

1000 g

Minerals Nutrients

Decomposers

Organic debris

Figure 101. Trophic pyramids.

I.1. PRIMARY PRODUCERS

The most important group of vegetable organisms in a fish pond is the phytoplankton. It is composed by a wide variety of aquatic algae which are free in water (without substrate). These algae are made up either of a cell (unicellular) or several cells (pluricellular) (Figure 102 below). Their presence in very great number gives blue green to maroon green color to the water of the pond. The phytoplankton has two very important functions in a fish pond. Firstly, it is an oxygen producer and secondly, it is the first link of the food chain in a fish pond. Algae are photosynthetic organisms that convert light energy into chemical energy, while consuming carbon dioxide (CO2) at night, like any organism and producing oxygen (O2). This process occurs only during the day with the presence of sunlight. The life of these organisms is relatively short and phytoplankton biomass vary with the characteristics of the environment such as temperature,

10 µm Filamentous algae

Unicellular algae

10 µm

10 µm

1 mm Colonial algae

Multicellular algae

Figure 102. Differents algae.

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presence of mineral elements, the illumination… The filamentous algae in too great concentration are to be removed in the ponds. If the mass of the vegetable organisms (phytoplankton and aquatic plants) in the pond is too important, it can consume oxygen at the expense of fish growth. At dawn, one can observe fish coming to seek oxygen at water surface and even sometimes, a massive mortality by asphyxiation. Figure 103. Aquatic plants The higher plants can become serious indi(To avoid in ponds). rect competitors of the fish production in pond, either by breathing during the night, or by the consumption of minerals, or finally by the shelter which they offer to the predatory organisms. The immersed plants, the emerged plants and the floating plants are distinguished (Figure 103 above). They are generally not useful in the pond except for the farming of herbivorous fish. By the use of minerals, these elements are not available any more for the phytoplankton, basic link of the food chain of the pond. In the same way, the cover formed by the higher plants decreases the penetration of the light in water, which reduces the capacities of photosynthesis of the phytoplankton and thus its development. The presence of some herbivorous fish can limit their proliferation. So in spite of these, the higher watery plants appear, it will have to be removed as quickly as possible. Emerged plants

Float plants

Submerged plants

I.2. THE INVERTEBRATES

The algae are used as food with the microscopic herbivores: the zooplancton. Itself feeds the consumers of 2nd order: carnivores. They consume wastes, phytoplankton, bacteria and for largest, other zooplanctonic organisms. Many organisms live close to the bottom which one calls benthos.

I.2.1. THE ROTIFERS

Rotifers are small organisms measuring between 50 µm and 3 mm which often have the shape of trumpet, cylindrical or spherical. They have two crowns of lashes around their mouth as well as an organic system specialized with in particular a digestive tract. They neither are segmented nor metamerized. The body is covered laterally by a resistant cuticle which sometimes becomes a true shell. They live mainly in freshwater but some species occupy marine waters as well as wetlands. They feed mainly on micro-organisms in suspen-

Figure 104. Rotifers. Adults

Juveniles

Big size

Small size Pest

Cladocerans

Figure 105. Crustaceans. 116

Subsistence fishfarming in Africa

Copepods

4. FISH FARMING sion in water. Some rotifers are parasites of crustaceans, molluscs and annelids. They compose most of the zooplankton of freshwater and constitute a source of important food in the fresh water ecosystems (Figure 104, p. 116).

I.2.2. THE CRUSTACEANS

Part of the organisms Adult composing the zooplankton are small crustaceans which are mainly divided in two classes, in ascending sizes. It distinguishes the cladocers and the copepods (Figure 105, p. 116 ). The zooplanDytiscus kton form an excellent food for many fish species especially during the larval stage. However, the largest copepods are predators of eggs, larvae and even of fry. It is important to know the dynamism of development of the Dragonfly groups composing the zooplankton. One will be able to also find in water some crustaceans which are parasites of fish and predators. Moreover, the presence of crabs and shrimps are not to exclude Figure 106. Insects. if they pass the filter. After the setting in water of a well fertilized pond, one observes during the first days a good development of the population of the class of smallest zooplankton, the rotifers. It is only after one week that the population of the cladocers reaches its optimum and the same, after ten days for the population of the copepods.

Larvae

4 to 8 mm

10 to 20 mm

I.2.3. THE INSECTS

A large part of the aquatic invertebrates are insects (Figure 106 above). Most of the time they are larvae such as mosquitos, dragonflies, flies, ephemers, trichopters… which have a phase of larval aquatic life and, after emergence, will spawn in water. By this cycle, some are vectors of serious human diseases like malaria (mosquito) either the onchocerciasis or river blindness (simulis). Some also are predators of fry. Some insects have an aquatic life as adults like the water beetles (Dytiscidae) and the water scorpions (Nepidae). They are also, often the predators of fry.

I.2.4. THE MOLLUSCS

There are a number of aquatic molluscs (Figure 107 opposite). You can find water snails and mussels Anodonta or freshwater. Snails can be predators of fish eggs. They are also the vector of a parasitic disease, schistosomiasis.

Figure 107. Molluscs.

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I.2.5. OTHER INVERTEBRATES

Other aquatic organisms can be found hydraires, parasitic worms (helminths, platyhelminths), leeches, sponges and even jellyfish. Some are predators of fish fry.

I.3. THE VERTEBRATES

Among the vertebrate ones, it is clear that the most represented are the fish with more than 10 000 freshwater described species in the whole world. One will reconsider the biology of some useful species in fishfarming. One will find also, well represented, the amphibians as frogs and toads which have an aquatic larval phase (Figure 108 below). Many tadpoles are herbivorous, but there are some which are predators and can feed on small fish. Among the reptiles, several snakes like the grass snakes and certain turtles are predators of fish. Finally, there exist several species of piscivorous birds like the kingfishers, the pelicans, the cormorants, the eagles, the herons which are effective predators of juveniles and adults fish. Finally, a mammal, the otter, which is a large fish predator.

Amphibians (frogs)

Reptiles (snakes, turtles)

Birds (eagle, herons)

Mammals (otter)

Figure 108. Vertebrates other than fish.

II. THE FERTILIZATION A clear natural water does not contain a food for fish. The water of the pond is like the agricultural land: if the ground is fertile, the plant grows well. To make water fertile, it is necessary to bring there fertilizing elements of which phosphorus in priority. A water will answer much better to the fertilization when its initial physical and chemical characteristics (temperature, pH, dissolved oxygen…) are close to the optimal ranges of the selected species. The fertilization is to increase the production of natural food in a pond, which makes possible to the fish to find what to feed itself in larger quantity. The fertilization consists in providing food to the living organisms of the pond which will be used as food for fish. When one uses manures to increase the fish production of the ponds, one will try to establish and maintain a dense population of phytoplankton and zooplankton, which should give a beautiful green color to water

II.1. THE FERTILIZERS OR MANURE

The action of organic manures is a little more complex. One distinguishes at least three functions for this type of manures which are (Figure 109, p. 119): ÖÖ To be used as fertilizing matter, ÖÖ To be useful partly, of direct food for some fish species as tilapia, but also for part of fauna living in the pond, ÖÖ To be used as support for a range of populations of microscopic organisms, part of fish natural foods. The fertilizing function of the organic manure is progressive because the minerals contained in this manure are made available to the phytoplankton only progressively of its decomposition until its complete mineralization. Several kinds of organic matters, most of the time of waste, can be used like organic manures.

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4. FISH FARMING Most current are the following ones: 99 Animal manures, mostly from the animals of the farm; 99 Waste of slaughter-house; 99 Fermentation of cassava; 99 Natural vegetation; 99 Compost, a mixture of various kinds of organic matters.

II.1.1. ANIMAL MANURE

CO2

CO

2 They constitute an additional source of carbonic gas (CO2), which is very important for the Zooplankton effective use of the nutritive elements present in water. They increase the abundance of bacteria in water, which accelerate the decomposiBacteria tion of the organic matters, and are also used as food for the zooplankton, which in its turn also increases in abundance. They have beneficial effects not only on the structure of the soil of the bottom of the pond but also on benthic fauna like the larvae of chironomids. However, the animal manures have some disadvantages, Benthic fauna most of the time related on their low content of primary nutrients, for their negative effects on Figure 109. Beneficial effects of the dissolved oxygen content and to the reserve organic fertilizers. of some fishfarmerss to use livestock wastes directly in the fishponds. The chemical composition of the organic manure varies considerably according to the animal of which it comes - with knowing the species, the age, the sex, its type of food - and according to the way in which the manure is treated, i.e. its relative freshness, the conditions of storage and the dilution rate with water. Chicken droppings are very rich in nutritive elements. The dejections of pig are usually richer than those of sheep or goat. The dung of cow and horse are poorer in nutritive elements, in particular when the animals eat only grass. Their fiber contents are relatively high. The excrement of buffalo is the poorest manure of all. The manure should be easy to collect. The animals under shelters or in enclosure produce a manure more concentrated than those which are in freedom. One can design the shelters of animals in order to improve the collection and the distribution of the manure towards the ponds. The sources of animal organic manure are rather numerous, but often in rather small quantities (Table XXIV and Table XXV, p. 120). This includes: 99 The chicken droppings and other birds are dispersed often too much in rural environment to be exploitable in the large ponds. 99 Manure of pig which is usable only by non Muslims. Association pigsty and fishfarming are very interesting by the outputs and the facilities which it gets. One will let dry this manure during 2 weeks before using it. 99 The manure of cow and other ruminants which is to be used with many precautions because they are too rich in cellulose and risk to cause an important fermentation which will make fall brutally the oxygen rate. It is preferable to use it in application on the bottom of the ponds, dry after draining. A scarification of the plate makes it possible to mix the manure with the mud without turning over the ground. 99 Liquid manure is a liquid oozing of a heap of manures after a rain or a watering is only found in the breedings where one collects the urines and the manure. It is excellent for the production of zooplankton at a rate of 2.5 liters/are/week. In the event of ammoniacal odor, it is necessary to reduce the amounts by half. The amount of animal manure to apply in a given pond varies considerably according to factors

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like the climate, the water quality and the soil, the characteristics of the manure and the type of regime (standard fish, density of fish, length of the period of farming). It is, however, impossible to recommend a treatment which is valid in all circumstances. Spreadings must beings uniform to avoid any annoying concentration. The choice of manures is fixed by the availability and the price, if possible no one. Each manure must be the subject of tests to check its productivity and its not-harmfulness. The spreading of droppings is carried out preferentially in weight of droppings and expressed as a percentage of the fish biomass. Should not be exceeded the recommended maximum values. This to initially avoid an accumulation at the bottom of the pond and then a fast fall of the oxygen rate. The ideal frequency of the contributions follows the rule: as often as possible. Best is a daily application. As an indication, in the small rural ponds of 100 m2 to 300 m2, the distribution is done once, or preferably twice by week. If one does not use of the manure every day but only once per week, that does not want to say that it is necessary to spread of them seven times more in only once in the pond.

II.1.2. OTHER ORGANIC MANURES

Several organic manures others that the animal manure are usually used on the fishfarm of small size. These manures are usually waste which one can get for few expenses and locally. Organic manures most usually used are: ÖÖ Waste of slaughter-house, such as contents of bovines rumen, blood, bone and enriched waste water. ÖÖ Agro-industrial waste, such as seeds of cotton, molasses, oil cake oilseeds and residual palm oil mud (4 to 5 % of nitrogen). Waste like the rice balls, bagasses of sugar cane and the sawdust are rich in cellulose, which decomposes very slowly in the pond. ÖÖ Retting of cassava. Cassava tubers of the bitter species that one can let soak in the ponds to remove the hydrocyanic acid from it before consumption, constitute an excellent way and at a cheap rate to fertilize the small ponds. The cassava then is recovered and consumed. The fertilization comes from the juice of steeping and is thus free. A minimum contribution of 10 kg tubers/are/day is recommended. The amount can reach 200 kg/are/week but no more. Table XXIV. Maximum amount of fresh solid manure per day in 100 m2 pond. Solid manure

Maximum amount (kg fresh/100 m2 /d)

Duck

2.8

Chicken

4.8

Pigs

Pig

6.0

Small ruminants

Sheep/Goat

3.4

Buffalo

6.3

Cattlel

6.0

Horse

5.2

Poultry

Large ruminants

Table XXV. Quantity to spread per type of manure. Source

For a pond of 400 m2 (4 ares)

% fish biomass

Poultry

Poultry droppings

4.5

½ to 1 wheelbarrow/week

2à4

Pigs

Pig dung

6

½ to 1 wheelbarrow/week

3à4

Small ruminants

Sheep or goat dung

3

Large ruminants

Cattle or horse dung

5

Cattle or horse stable-litter

15

Manure of large ruminants Liquid manure

120

Quantity (kg/100 m2)

Subsistence fishfarming in Africa

1 tonne/year 10 l/week

4. FISH FARMING ÖÖ The vegetation which was cut in the pond itself, the channels or other water places. In some areas, harmful floating plants like the water hyacinth (Eichornia crassipes), the water ferns (Salvinia sp.) and water lettuces (Pistia sp.) can be used effectively. ÖÖ The compost produced apart from the ponds can be spread out over the bottom of the pond drained before the filling, or be used regularly to fertilize water. The vegetation such as graminaceous crossed, vegetation wastes and fruits in decomposition can be used to manufacture a simple compost in the pond itself. The average quantities of these organic manures to apply to the small ponds are indicated in Table XXVI (below). They should be used regularly, while avoiding overloading the pond for several weeks. It will be necessary to check water quality to adjust the quantities used.

II.2. THE COMPOST Composting is characterized by the intensive decomposition by organic matter micro-organisms, in general under controlled conditions. This process allows to use a whole range of waste, residues and natural vegetation at a cheap rate for the production of a clean product, dry and rich in primary organic matters and nutritive elements. This product is called compost. The manufacture of compost is carried out via various groups of micro-organisms as bacteria, mushrooms and protozoa, which need mainly carbon (C) and nitrogen (NR) for their development. It is to obtain these substances which they decompose the organic matters available. The compost are composed of relatively tender plants like the leaves, grasses and aquatic plants, which one mixes with feces (of birds, pigs, herbivores or human). The compost can be produced under anaerobic conditions (in the absence of oxygen) or aerobic (in the presence of oxygen). Each type shows specific characteristics (Table XXVII, p. 122). In some agricultural systems, one uses the two types of composting, for example the aerobic preparation in the parts external of material and the anaerobic preparation in the interior zone where there is little oxygen. In fishfarming, composting is usually practiced in two ways: ÖÖ Simple composting aerobic/anaerobic underwater, in heap. ÖÖ Dry composting aerobic, either in heap, or in pits. To prepare the compost on ground, it is easier to use the aerobic method (Figure 110, p. 123). It is then important to ensure that there is always air in the heap of compost to maintain a fast and total decomposition of organic matters. For this purpose, the stages will be of: 1. To start to constitute a new heap of compost while placing a first layer of coarse vegetable matters, for example of the rachis of leaves of banana tree, straw or stems of sugar cane, on a height of at least 25 cm. This layer should allow the circulation of air while absorbing the liquids rich in nutritive elements coming from the upper layers. 2. To cut the matters used for the compost of small pieces from 3 to 7 cm.

Table XXVI. Organic fertilizers commonly used in small-scale fish farming. Organic fertilizer Animal manures Slaughterhouse wastes Agro-industrial wastes Cassava tubers

Average amount applied at regular intervals See Table XXIV and Table XXV, p. 120 10 kg/100 m2/week 8 kg/100 m2/week 50 to 100 m3/week 10 to 25 kg/100 m2/day

Vegetation

20 to 25 kg/100 m2/week

Compost

20 to 25 kg/100 m2/week 50 kg/100 m2 pond bottom

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3. To pile up without packing all the matters, by leaving space between the layers. One never should compact the heap of compost. One should not make a too high heap to avoid a packed under its own weight. 4. To maintain the heap moist but not wet. Too much water would prevent the air circulation. It will be necessary to protect the heap from the rain (too much wet) and the sun (too much dry). 5. To turn over the heap of time to other to air it and avoid a production of too intense heat in the center. One introduces a piece of wood in the middle of the heap and one waits a few minutes before withdrawing it. If the heap is too hot, dry or too odorous, it is time to turn over it There are two ways of piling up materials: ÖÖ In heap above the level of the ground, preferably during the seasons of strong rain. It will be then easier to turn over and maintain ventilated, but the carbon and nitrogen losses are high, or ÖÖ In pits dug in the ground, a place raised to avoid the floods. They will have to be protected by trenches, if necessary. It is preferable under dry climates to retain moisture. The carbon and nitrogen losses are weaker.

II.2.1. THE LIMING

The earth ponds are conditioned by liming, i.e. by preparing the ponds and by treating them with various types of amendments limestones, chemical substances rich in calcium (Ca). Liming improves the structure of the ground of the pond, improves and stabilizes water quality and allows that manures are more effective to increase natural food available. One of the most important effects, that one can measure and use to control liming, is that which modifies the total alkalinity of the water of the pond. The total alkalinity of water is the measurement of its total concentration out of carbonates and bicarbonates of substances like the calcium (Ca) and the magnesium (Mg) which are typically alkaline. The liming of the ponds is not always necessary. One can do it on a new pond or a pond already used. In certain cases, it can not only be one money wasting, but also prove to be harmful with fish. Before making a decision, the pond will have to be studied attentively as well as the particular characteristics of its water and its ground. The following points will be checked: 99 If the pH of the ground of the bottom of the pond is lower than 6,5, liming is justified. 99 If the bottom of the pond is very muddy because it regularly was not emptied and was drained, liming will improve the conditions of the ground. 99 If there is risk which a contagious disease propagates or if it is necessary to fight against of the enemies of fish, liming can help, in particular in the drained ponds. 99 If the quantity of organic matters is too high, either in the ground of the bottom, or in water, liming is advised. 99 If the total alkalinity of water is lower than 25 mg/l CaCO3 liming can be justified. Table XXVII. Particular characteristics of composting methods. Characteristics

Anaerobic composting

Necessary

No

Losses of nitrogen

Important

Reduced

Losses of carbon

Important

Reduced

Production of heat

Important

Very small

Destruction of pathogens Moisture content

Composting method

122

Aerobic composting

Presence of oxygen

Subsistence fishfarming in Africa

Yes

No

To be controlled, best 40-60%

Not importante

In heap, above ground level

In heap. deeper under water

In pit, below ground level

In sealed heap, above ground level

In heap, at water surface

In sealed pit, below ground level

4. FISH FARMING

Air should always be  present within the  composting pile keep moist  but not wet

Pile not too high

Finely cut and loosely  packed material

Protect from sun  and rain

AIR First layer: very coars material

25 cm

… if too hot or smelly,  turn pile over

Check composting process: drive stick in…

Pile up composting material…

…or in pits

Figure 110. Preparation of dry compost.

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The effects on the ground of the bottom of the pond are: ÖÖ An improvement of the structure; ÖÖ An acceleration of the decomposition of the organic matters; ÖÖ An increase in the pH. All these factors will involve a faster and more important exchange of minerals and nutritive elements between the ground of the bottom of the pond and water, at the same time a reduction in the demand for dissolved oxygen. Usually, the amendments limestones and manures are applied separately. It will thus be necessary to lime at least two weeks, and preferably a month, before any spreading of manure. Annual liming will thus be carried out at various times of the year according to the calendar of management of the pond. In tropical climates, it is preferable to lime the pond as soon as the fish was collected and at least two weeks before putting fish again. Manures are applied then, 15 to 30 days after liming. However, measurements of the pH and alkalinity, even if they are current, will not be inevitably accessible for the recipients, who will be able to then address themselves to local laboratories and institutes. For NGOs, kits of analyzes are easily available in the trade and not very expensive.

II.2.2. THE SPREADING

It is possible to spread manures either dry, or when the pond is fill of water. A certain number of methods concern the site and the distribution of the animal manure in various situations (Figure 111, Figure 112 and Figure 113, p. 125). However, the illustrated examples are general and must be adapted to the local conditions (quality and quantity of manure available, water quality, weather conditions…). Except for waste of slaughter-house and tubers of cassava, organic manures are thus piled in one or more heap in water. One can also use an enclosure in a corner of the pond. Organic manure is piled up and compacted inside, in order to start a production of underwater compost. It had been already seen how to make compost in aerobic. One can have a compost in anaerobic (paragraphe II.2, p. 121). For that, in each pond, one arranges a composting heap in bamboo or wooden to retain manure. One will place it in an angle, in the major part of the pond (Figure 115 and Photo N, p. 126). The heap must be well packed underwater, for example by trampling each layer carefully (Figure 114, p. 125). But it will have to exceed water surface slightly, since its height will decrease slowly. Each week, it is necessary to add new layers of matters to reconstitute it. To obtain very good performances: ÖÖ To use at least a heap of compost by 100 m2 of pond. ÖÖ To take care that the total surface area of the surface of the enclosures with compost corresponds to 10 % of the surface of the pond. ÖÖ To turn over the heaps all both or three days. ÖÖ To place the sufficiently deep water heaps.

II.2.3. THE «GREEN WATER»

Once the ponds out of water and are fertilized, it thus should be waited until the natural cycle of the pond is set up. For that, one will wait several days during which, in the event of good fertilization, water will become green, i.e. rich in phytoplankton. To know if water is sufficiently green, one can use a disc of Secchi (paragraphe II.1.2, p. 48) or quite simply to plunge the arm in the pond to the elbow. If one distinguishes hardly the end from the fingers, it is that water is sufficiently green. The pond is now ready for receiving fish.

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4. FISH FARMING In heaps In rows

A

B

C

D

Figure 111. Applying animal manures to a drained pond bottom. A: New pond; B: Pond in which the water is badly controled; C and D: Pond in which the water is well controled (most common case).

10 m 1m

A

B

C

D

Figure 112. Applying animal manures to water-filled ponds that have been stocked (I). A: Distribution of liquid animal manure from the banks; B: Distribution of animal manure using an inner-tube and basket; C: Disposition in heaps along the banks; D: Detail of an elongated crib.

A

B

Figure 113. Applying animal manures to waterfilled ponds that have been stocked (II). A: Stacking animal manure mixed with stablelitter in heaps along the banks; B: Applying pure animal manure from a boat. Fill up to the surface of  the water and well  compress

Figure 114. Preparation of an anaerobic compost.

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Installation of a crib in  each of the two shallow  corners  

Figure 115. Compost heap in crib in a pond.

Photo N. Compost heap. [Up, Liberia © Y. Fermon], [Down, © APDRA-F](CIRAD).

III. SUMMARY ÖÖ The two steps are: ÖÖ The fertilization ÖÖ The expectation of a « green water » which indicate that the pond is ready for ensemensement ÖÖ Emphasis on: ÖÖ The preparation of aerobic and anaerobic compost

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Chapter 09

THE HANDLING OF THE FISH Once the pond is ready, stocking may take place (Figure 116, p. 128). The reader will find in Appendix 04 p. 239 information on the species of fish used in fish farming in Africa according to the basins and countries. Consider again the sequence of operations, activities will be in the following order: 14.  Collecting tilapia        • In the field • By propagation 15. Juveniles storage 16. Transporting live fish 17.  Stocking tilapia 18. Following the fish 19. Stocking with other species 20. Draining and harvesting In a certain number of cases and areas, it is rather easy to get tilapia fingerlings in the wild. Otherwise, one will choose to produce fry from broodstock collected in the wild. The assessment previously carried out will indicate which are the species usable close to the selected sites: ÖÖ To limit the loss of fish; ÖÖ To limit the costs. A transport on long distance requires a logistics which can be costly. One will try to limit the maximum displacements. Insofar as the majority of the fingerlings producers currently in Africa do it without real genetic management of the broodstock and, moreover, starting from introduced species, and in order to limit the costs, one will avoid most of the time providing oneself in fingerlings from local producers

I. CATCH METHODS On a fish farm, live fish have to be handled on many occasions, for example during routine monitoring of their growth and health, transfer from one pond to another and final harvesting. This handling usually involves the use of various nets and other small pieces of equipment. However, it is necessary to remember some points mentioned above. ÖÖ If they are beneficiaries who will make the catch, the difficulty will be to make them understand that it is not necessary to look for fish elsewhere than at home. ÖÖ One of the main principles will be to use only non-destructive gear for the local wildlife. ÖÖ Care should be taken to respect the laws relating to fishing. Where appropriate, permits have to be requested from the local authorities.

To get wild specimens, the help of local fishermen who can be, sometimes, also beneficiaries can be requested. In general, they know well the places of possible capture of the various species. If necessary, one will be able to manufacture small fishing gears.

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0

3 months

Assessment Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Duration: 3 months

Selection Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Draining channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas Duration: 6 - 9 months 3 to 6 months

Completion and filling in water

Fish farming Fertilization

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Maintenance and  follow-up of the  ponds

Stocking with tilapia Follow-up  of the fishes

7 - 10 months Duration: 4 to 12 months

Stocking with  predators

End of the cycle 11 - 22 months

Outside composter

Storage of  fishes Duration: 0.5 to 1 month

Draining of the pond  and harvest Sale and\or transformation  of the fish

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Figure 116. Setting of fish pond: 4. Fishfarming and 5. End of cycle.

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Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

4. FISH FARMING

5. END OF THE CYCLE

I.1. SEINE NETS

One of the main gear to catch is the seine. It is the easiest way to catch fry. If a seine of meshs of approximately 1 cm is used, the fish catch will have at least 5 cm length. To collect juveniles, one will use seines made with mosquito net. A seine net is the most common type of net used on fish farms to harvest fish. It is a long net with ropes at each end and is pulled along the pond to collect the fish and then drawn into a circle to trap them and, most often, bring back to the shore.

Head rope  with floats

Mounting twine

Depth of net

A seine net consists of one or more pieces of netting material mounted (Figure 117 opposite): 99 At the top on a head rope equipped with floats; 99 At the bottom on a foot rope equipped with sinkers (or leads).

Netting

Mounting twine

Foot rope with 

These ropes are normally extended beyond sinkers the netting to form pulling ropes. There are several kinds of seine. The two Figure 117. Diagram of a seine. following designs are most commonly used. ÖÖ The seine is made similarly over all its length. It consists of a single rectangular netting panel. ÖÖ The seine is made of three parts: ¾¾ One central, loosely mounted bag to collect the fish; ¾¾ Two lateral wings to lead the fish towards the central part. To be able to make a net, various materials are necessary (Figure 118, p. 130).

Rope can be made either of natural fibre (hemp, manila, sisal) or synthetic fibre (polyamide, polyethylene or polypropylene). Synthetic fibres are stronger and more resistant. Rope can be either twisted or braided. Floats can be made of several materials such as light woodpaint or tar it to keep it from becoming impregnated with water, which would reduce its floatability; cork; plastic.In short, of a material which floats Sinkers are usually made either from baked earth or lead. In this last case, they are available as thin lead sheets or in the form of olives of various individual weights. Lead recovered can be used. A total weight of sinkers equal to 1 to 1.5 times the total floatability of the floats is need. Small stones can also be used, but they may break more easily. For the assembly, one will put a float every 10 to 25 cm maximum. For the sinkers, one every 3 intervals. Various stages are necessary to mount a seine (Figure 118, p. 130). A small seine may be handled by as few as two people, one at each end of the net, who hold the net vertical with the wooden poles (Figure 119, Figure 120 and Figure 121, p. 131 and Photo O, p. 132). f no poles are used, take care to keep the bottom rope slightly ahead of the top rope. With a muddy pond bottom or with a larger and heavier seine, additional strength may be needed. In this case, one person pulls at each end pole of the net while others assist by pulling at the extended end ropes. It is useful to have an additional person standing near the middle of the seine while it is being handled to help whenever necessary, for example when it gets stuck on some underwater obstacle.

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Netting material Float Sinker

Twine

Net  needle

Rope

Netting

A Head rope 6 mm in diameter  and 11 m long

String floats on the head ope  and tie the rope between two  posts

150  cm

B Attach netting material  with a net needle

Non-slip  knot

Normal  knot

C

Seines can be rather expensive pieces of equipment. To keep them in good condition a good care of them should be take. Watch especially for the following. Protect them from direct sunlight and dry them in the shade. After seining, clean and rinse them well, removing all debris and fish slime, scales, etc. Protect them in a cool, dry place such as an open shed. Protect them from rats and mice, for example by hanging them on horizontal bars above ground level. Repair them regularly. Replace a section of netting it necessary.

D Begin to attach netting to  the head rope 9 meshes

8 meshes 8 meshes

Float

E

ÖÖ Note that the use of seines is generally prohibited in the wild. If this is not the case, it will have to be used only for the harvest of fingerlings or broodstock. If applicable, authorization must be obtained from the competent authorities.

Upright wooden pole

Tie the foot rope  between two posts  and begin to attach  bottom part of  netting

20 to  30 cm

F Placement of floats and sinkers

Head rope  with floats

43 2 1 4 3 21 4 3 21 4 3 21

First float Tie side rope  next to frst  knot

Tie side  rope to  pole

Side  rope Foot rope  with sinkers

Notch

3 2 1 3 2 1 3 2 13 2 13 2 1 3 2 1

G

First sinker

Figure 118. The differents steps to construct a simple seine.

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Join the head and  foot ropes and add a  pulling rope

Figure 119. Setting of the pole to hold the seine.

4. FISH FARMING 8 m

5. END OF THE CYCLE

7 m

8 m

2 m

Wing

1.30 m

Aile

1.30 m

Central section When the three parts are assembled a bag  shape is formed in the central section 23 m

Bag shape

Figure 120. Construction of a central-bag seine.

Pulling the seine  from both sides of  the pond

Larger and heavier  seine nets will need  more people to  handle

A

A Two people using  a small seine to  catch fish

B

Keep the fish in the net  and move it towards  the bank

C

Take in the net and  enclose the fish in a  pocket

D

Transfer the fish to  a container using  a hand net

E

E Figure 121. Manipulation of a seine.

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Photo O. Use of small beach seine (Liberia, Guinea, DRC) [© Y. Fermon].

I.2. GILL NETS

One of the most widely used nets in freshwater capture fisheries is the gill net, which may also be useful on a farm for selective harvesting of larger fish for marketing.

Photo P. Mounting, repair and use of gill nets (Kenya, Tanzania) [© Y. Fermon].

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5. END OF THE CYCLE Take a fish the  size you want to  catch and tie a  piece of string  around its  thickest part…

…the mesh size should be a  little less than this

A gillnet stretched between  two posts in midwater

Figure 122. Gill nets. A gill net is very similar in overall shape and design to a seine net. The netting twine is thinner and usually made of synthetic monofilament such as polyamide monofilament with a diameter from 0.12 to 0.25 mm, depending on the opening of the mesh. Mesh size is determined by the size of fish to be harvested. Fish should be able to pass through the extended mesh just beyond their gill covers but not further. (Figure 122 above and Photo P, p. 132). When they feel caught and try to back out of the mesh, their gill covers should be caught by the mesh sides (thus the name gill net). Such nets are highly selective. The mesh size is calculated by measuring the body perimeter, or girth, of a few fish of the size you wish to harvest. Your gill net should have a stretched mesh size about a quarter smaller than the fish girth. Gill nets of stretched mesh size less of 4 cm or de 2 inches have to be avoid, for not catching too small fish. It is important to check and remove the gilled fish maximum every hours if one want to get the fish alive and not too damaged.

I.3. CAST NETS

Another non-destructive fishing gear and often used by the fishermen for the fish capture is the cast net. It is quite useful to capture fish of large size without damaging them. A cast net consists of a flat circular piece of small-mesh netting heavily weighted along its periphery with sinkers. Usually a series of strings run from the outer edge through a central ring to join into a single pulling rope. As it is not very easy to make, you can buy your cast net from a specialized store. Skill is required in the handling of a cast net (Figure 123 and Photo Q, p. 134). It should be thrown well opened and horizontally on to the water surface. It sinks rapidly to the bottom, and is closed by pulling on the central rope, entrapping the fish inside the net. A cast net can be used either from the banks, in the water or from a boat.

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Open  net

Closed  net

Use a castnet  in the water

Photo Q. Cast net throwing (Kenya, Ghana) [© F. Naneix, © Y. Fermon]. Use a castnet  from a boat

In position

Closed

Figure 123. Use of a cast net.

I.4. DIP OR HAND NETS

Dip nets are commonly used on fish farms for handling and transferring small quantities of fish. They can be bought complete, assembled from ready-made parts or you can make the nets yourself. A dip net is made of three basic parts (Figure 124 and Photo R, p. 135): 99 A bag, made of netting material suitable in size and mesh type for the size and quantity of fish to be handled; 99 A frame from which the bag hangs, generally made from either strong galvanized wire or iron bar (usually circular, triangular or «D» shaped, with fixing attachments for the handle);

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Round

Square or rectangular

Half-round

Handle Frame

Photo R. Dip net (Guinea) [© Y. Fermon]. 99 A handle, made from metal or wood and 0.20 to 1.50 m long, depending on the use of the dip net.

Bag

Figure 124. Different types of dip nets.

The size and shape of dip nets vary greatly. It is important to keep the following guidelines in mind. Handle live fish using dip nets with relatively shallow bags. Their depth should not exceed 25 to 35 cm. One will have to select a size suitable for the size of fish to be handled.

I.5. TRAPS

There are many different kinds of traps commonly used when fishing in lakes and rivers in the wild. It might be the case to catch broodstock or associated species as catfish. Certain kinds may be useful for simple and regular harvest of food fish without disturbing the rest of the pond stock. These traps are usually made with wood, plastic pipe, bamboo or wire frames, with netting, bamboo slats or wire mesh surfaces. There are two main types (Figure 125 opposite and Photo S, p. 136):

Opening: 25 to 30 cm Length: 80 to 100 cm

99 Pot traps, which are usually baited and have a funnel-shaped entrance through which fish can enter but have difficulty escaping from; and 99 Bag or chamber traps, which usually have a guide net that leads the fish into a chamber and have a V-shaped entrance that keeps the fish from escaping.

Figure 125. Differents types of local traps.

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Photo S. Traps. On left and up on right, traditionnal trap (Liberia); Down on right, grid trap full of tilapia (Ehiopia) [© Y. Fermon].

I.6. HANDLINE AND HOOKS

One of the easiest methods to capture broodstock is just with a fishing handline. It is a selective gear which allow to capture and to maintain in life without problem fish like the tilapia. It will however be a question of using as much as possible hooks without barb.

II. THE TRANSPORT OF LIVE FISH Transport of live fish is common practice on many fish farms, used for example: ÖÖ After harvest of fish in wild; ÖÖ To take fish to short-term live storage. The duration of transport varies according to the distance to be covered: 99 From the river, transport time is usually longer, varying from a few hours to one or two days; 99 On the farm, transport time is usually very short (a few minutes) to short (up to 30 minutes). There exist certain basic principles governing the transport of alive fish: ÖÖ Live fish are generally transported in water. The quality of this water changes progressively during transport. Major changes occur in the concentration of the chemicals. ¾¾ Dissolved oxygen (DO) is mainly used by fish for their respiration. Bacterial activity and oxydation processes will also use oxygen in the presence of organic matter. 99 The oxygen consumption increase with the temperature. 99 The DO consumption by small fish for 1 kg is higher than fish a larger size.

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99 The oxygen consumption of fish resting is lower than stressed or in activity fish. ¾¾ Ammonia is excreted by fish and produced by bacteria in different forms. The most toxic form, free or non-ionized ammonia (NH3), becomes more important as water temperature and pH increase. ¾¾ Carbon dioxide (CO2) is produced by fish as a by-product of respiration. Bacteria also produce CO2 .Carbon dioxide exists in different forms; the most toxic form, free CO2, increases as water pH decreases. Other changes in water quality may also take place during transport. 99 Increased water temperature in warm climates increases oxygen consumption and the content of toxic free ammonia. 99 Increased carbon dioxide content and thus decreased pH, reduce toxic free ammonia but increase the content of toxic free CO2. 99 Increased suspended solids from fish waste. ÖÖ Water quality ¾¾ A cool water, so fish and bacteria will be less active, thus reducing DO consumption and production of ammonia/carbon dioxide. Ice may be use if necessary. One will avoid to expose the fish to a sudden change in temperature. ¾¾ A clear water which is free from silt or suspended solids, to reduce stress to the fish gills, to reduce bacteria in organic solids, and to reduce risk of low oxygen levels caused by decomposition of organic material. As far as possible, it is necessary to avoid handling fish with the hand too much because its destroys the mucus which they have on the body and to leave them too a long time out of water. For transport itself, of short and medium time, one can use clay pots or barrels, buckets or basins but also plastic bags inflated with the air. For Clariidae, just a small amount of water is enough because of their capacity to be able to breathe the ambient air. In the case of long time transport, one will used plastic bags inflated with oxygen, with the air if no oxygen (Figure 126 and Photo T, p. 138). One can get oxygen in a carriage-builder who makes welding either in a dispensary or a hospital. As much as possible, each breeder will have to be alone in his bag and, for the juveniles, one will limit the densities. However, it is true that this will increase volume to be transported, thus, the risks of mortality are largely reduced. One should not put too much water in the bag. A level just above fish is enough amply. One counts, in general, 1/3 of water for 2/3 of air or oxygen. For just catch fish, one will change the water of the container every 5 mn or when the fish pipe on the surface, to evacuate the organic waste rejected by fish because of the stress of their capture and which consume the oxygen of water and this, very quickly. There exists a certain number of precautions to be taken and actions to be undertaken: For transport in the medium and long term, before transport, when the fish come from the ponds, one will keep them in stables, in hapas for example, without food and one will keep them long enough so that their digestive tract is completely empty. Water in which they will be transported will remain thus cleaner. The minimum duration of the period of fast depends on the temperature of water and the species. In warm water, a duration from 12 to 12 midnight is sometimes sufficient. It is not necessary for transport of short duration. One will avoid, as much as possible, to dirty the water of transport. It will thus be necessary to carefully clean the fish with clean water before loading them into the container with transport. One will place the containers in the darkness and safe from sudden noises to maintain fish quiet during the transport itself. Wherever possible, one will maintain fish cool during transport. There will be transport during the

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night or early in the morning. In the same way, direct solar light will be avoided and it will be preferably to place the containers in the shade. The containers can bec over with bags or wet tissue to increase the cooling effect of evaporation One should not feed fish during transport. As much as possible, the water of transport will be replaced by better oxygenated and fresher water, during long stops, if the fish seem disturbed or start to come to water surface to breathe, instead of remaining calmly at the bottom or when transport lasts more than 24 hours without additional oxygen contribution. If necessary, the quantity of oxygen in water can be increased by agitating water with the hand. The density of fish should not be too high to avoid a too strong oxygen uptake. For a bag of ½ liter, 3 or 4 fish of 2 cm but only one of 8 cm must be put in. Moreover, for fish subadultes and adults, wounds can be caused by the contacts and may result in the death of a fish. As soon as a fish died in a bag or a container, it should be removed quickly. For the release of fish in water, one will let the container soak in order to reduce the variation in temperature between the water of the bag and the water of the pond. Then, one will put water of the pond little by little in the container to finish the acclimatization of fish before releasing them.

Photo T. Fish packing in plastic bags (Guinea, (Ehiopia) [© Y. Fermon, © É. Bezault]. Regulator, valve  and air cylinder

Deflate bag  and close it  around  tube

Tube

Water

Water +  Fish

Water +  Fish

Air

Water + air  + fish

Figure 126. Fish packing in plastic bags.

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Tie

Pull  tube

Water + air  + fish

Air

4. FISH FARMING

5. END OF THE CYCLE

III. THE PRODUCTION OF FINGERLINGS OF TILAPIA It is possible to set up a production of fingerlings from broodstock collected in the wild. Indeed, it is sometimes difficult to be able to provide fingerlings in good number in the wild, for example, in rainy season. Three possibilities exist and vary according to the species. Fish can reproduce by: ÖÖ Natural, where one arranges a water level according to the behavioral needs and habitus of the species to be breed and then put the breedeers, ÖÖ Semi-natural with injection of hormones to start the production of the gametes in a simultaneous way, and, finally, ÖÖ Artificial where, after injection, the ovocytes and sperm are extracted manually to proceed to a manual fecundation. The reproduction and the production of tilapia are currently carried out in farming systems according to very variable levels of intensification, which depend on the topographic, physicochemical, and socio-economic conditions of the area. The various techniques used until now are presented according to the environment in which they are developed, namely: 99 Fish Ponds, 99 Hapas and cages, 99 Artificial tanks (basins), “raceways” and arenas, 99 Hapas in tanks, 99 Aquariums of experimentation. In the situation of subsistence fishfarming, one will choose preferentially the production in ponds and, if necessary, hapas and cages. It is necessary to take account of the behavioral needs of the tilapia (Appendix 03 paragraph II, p. 216). They are territorial animals. For the mouthbrooders, in fact, the males defend a territory. For the substrate spawners, the two parents are territorial. Generally, one can consider that the size of the territories will be about 1 m2 on the ground. This size will increase with the size of the individual. However, individual variability is very important in these fish. From their biology, fingerlings from 10 to 15 mm length can be obtain every month. However, for mouthbrooders, it will be necessary to take care of the females which suffer the harassment of the males at the end of incubation. If they are requested too much, the guard of the fry will be shorter with a greater risk of fry loss.

III.1. THE RECOGNITION OF THE SEX

It is sometimes rather difficult to differentiate the sexes from fish. In some species like Alestidae, the sexual dimorphism appears on the anal fin. In many species of mouthbrooding Cichlidae, the males present a bright coloration. However, some non-dominant males keep a coloring close to that of the females. It is then necessary to look at the urogenital orifice while returning the fish (Figure 127, p. 140). When the breeding season comes, broodstock should be carefully selected. Only fish that are ready to spawn should be used. Select fish with the following characteristics: 99 Males should release a few drops of milt when the abdomen is slightly pressed. 99 Females should have a swollen and protruding genital opening, reddish/rose in colour, and a well-rounded and soft abdomen, showing that the gonads are developed up to the dormant stage. When there is risk of males agression (for example, in the case of catfishes), the fish of the two sexes must be kept in separate ponds after selecting them.

III.2. THE NURSERY PONDS

In the case of a central processing unit making it possible to provide alevins to the whole of the pisciculturists, one can propose with the local services the installation of a station of stocking with fish in pond. In this case, one will choose ponds whose surface varies between 1 and 5 ares with a depth from 0.4 to 0.5 m. Some authors recommend ponds of 4 ares, allowing a higher production, by unit of area, with that of the ponds of 0.5 are. Others on the other hand recommend the use of small

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Arrived at maturation

Milt drop

Anus

A - Maturation test

Urogenital papilla

Urinary orifice

Urogenital orifice

Anus Genital slit

B - Clarias gariepinus Papilla

C - Lates niloticus

Tail

Head

Genital papilla

Oviduct

Anus

Urethra

D - Cichlidae

Urogenital pore

Anus

Figure 127. Sexual differentiation of differents species.

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ponds from 9 to 12 m2 in which only one pair is introduced. The small size of these ponds facilitates the regular fishing of the fry groups at the end of the parental guard. These small ponds do not require a monk. It is the latter system which will be privileged. This method, for mouthbrooders, allows a production from 200 to 300 alevins per pair of parents and per month. It seems however that the frequency of the spawns and the fry production are seriously improved while installing in these small ponds 4 to 6 females with 2 to 3 males. That would in any case avoid the absence of production by sterility of one or the other breeder. In pond of 4 ares, the stocking is made with 200 females (average weight = 150 to 300 g) and 70 males (a.w. = 50 to 200 g), that is a density of 0.7 breeders/m2 and a sex ratio female/male of 3:1 (Figure 128, Figure 129 and Table XXVIII below). The reduction in the production of fry per kg of female, with the increase in the average weight of the females can be attributed to 3 factors: ÖÖ Decreased fertility with increasing weight. ÖÖ Decrease in the frequency of eggs with increasing weight. ÖÖ Decrease in the frequency of reproduction of males towards large females more aggressive. Regarding substrate spawners, the sex-ration must be reduced. Two techniques of harvest are generally used, either the regular draining of the ponds at interval of 60 days, in order to limit the frequency of the spawnings and separation of the breeders and the fry using nets of adapted meshs size, or the harvest by seining or using cast net allowing to collect all fingerlings of an average weight higher than 0.5 g. The exploitation begins 30 to 60 days after introducing the breeders and goes on at the frequency of a harvest every 15 days. From a biological point of view, one of the main advantages of obtaining fingerlings in pond is the optimal use of the resources of the pond, compared with the mode of breeding in more closed system. From a practical point of view, the breeding in pond is also of a simple technology, requiring a less regular control than a breeding in artificial conditions. However, with high densities, the Table XXVIII. Production of Oreochromis niloticus in function of the number of breeders in a pond of 4 ares – 122 farming days. Density breeders (ind/m2)

Fingerlings production

Sex ratio (female / male)

(ind/m /month) 2

(g/m2/month)

0.35

3

33.1

60

0.50

1

27.5

49

0.70

3

54.0

86

1.00

1

45.0

112

Nomber of fry/kg female/day

Fry production/m2/day

400

300

200

100

0

0

1

2

3

4

5

6

7

Genitors density (ind/m2)

8

Figure 128. Fingerlings produced per fish density in Oreochromis niloticus.

9

80 70 60 50 40 30 20 10 0

0

50 100 150 200 250 300 350 400 450 500 550

Females body weight (g)

Figure 129. Fingerlings produced per females body weight in Oreochromis niloticus.

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conditions of storage become more or less similar to those observed in cage or in tank and it is then necessary to carry out a more precise follow-up of the various phases of production: ÖÖ Control reproduction of the breeders and frequent harvest of fry, ÖÖ Improvement of the productivity of the pond by fertilization, ÖÖ Regular fish feeding, ÖÖ Control of the water quality and renewal of water if necessary.

III.3. HAPAS AND CAGES

Under certain conditions, depending mainly on the mesh size and the density of the breeders, the reproduction of the tilapia in cage is however realizable and has already led to very high productions of fry (Figure 130 below and Photo U, p. 143). Hapas are fixed pocket of small size (de 1.5×1×1 m à 3×3×1 m) made with mosquito net (mesh size of 1-3 mm) in nylon and attached to stick in bamboo, stakes or wooden stakes put into the bottom of a pond depth. The hapa is placed at 10-20 cm from the bottom of the pond and the depth is about 0.6 m. It can also be placed in a basin. Thus, the breeders are confined in an internal room delimited by nets with mesh size of 30 mm, so that the fry can be easily stayed in the external room (with 1-3 mm mesh size) as they are produced. This device presents the disadvantage of limiting the water flows through hapas, because the breeders do not have access to the walls of the external room. However, it is known that the movement of fish, like their action of algae and détritus scraping facilitate the water renewal within hapas. An alternative is to put the breeders in a half of hapas, which allow to ensure the breeders of good conditions of water circulation (Figure 131, p. 143). The best results are obtained with densities from 2.5 to 5.0 breeders/m2. The best results are obtained with sex ratio female/male of 5:1 to 7:1. Recently, however, of ratios 2:1 and 3:1 seems more advantageous.

Internal hapa

B

External hapa

A2

A1

Figure 130. Hapas and cages. A: Hapas, A1: Simple, A2: Double; B: Cage.

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A

B

5. END OF THE CYCLE

C

Figure 131. Differents systems of reproduction of tilapia in hapas and cages. A: Simple; B: Double with breeders in the middle; C: Breeders in one half. One of the advantages of the use of the system hapas is the facility of control of the spawnings and recovery of fry, each unit being easily handle by one or two people maximum. One can also get the fry every day with hand net. A good harvest interval will be from 10 to 14 days for females of one to two years old. The cages generally consist of a rigid framework of wood made support or of metal equipped with a synthetic net delimiting a volume of water and equipped with a system of floating attached to the upper framework or supported by stakes inserted in the lakes or river at a shallow depth.

Photo U. Hapas in ponds (Ghana) [© É. Bezault].

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The selection of the sites for the establishment of a breeding system in bcage is essential. Factors such as quality and circulation of water, adequate protection against the floating débris and the waves, accessibility of the site, safety and distance compared to the markets are important to consider. The brutal arrival of the first water of flood, extremely turbids, must also be taken into account, because it involves a degradation of the conditions of farming and a stop of the feeding of fish. A cover or a net of protection installed on the cage makes it possible to submerge it if necessary. Lastly, it will be necessary to be attentive with the presence or the absence of water currents within the cage, with the reduction in the concentration of dissolved O2 following the increase of toxic gases, and the important thermal variations during the transitional periods. Whatever the model used, the bottom of the cage must be at least at a distance of 0.3 m of the bottom where waste accumulates and causes a reduction in the O2 concentration. The cages for the reproduction and the fry production are generally smaller than those for the production of fish for consumption, which is in cages of 0.5 and 1 m3. The depth of the cage can also affect the growth and the reproduction of the tilapia. A depth from 0.5 to 1 m is generally observed for the production of fish for consumption in cages of 20 m3. Meshs size of 3 mm seem to be a high limit of size to observe the spawning of O. niloticus because the intermediate size of eggs is from 2.5 to 3.0 mms in diameter. The best production rate of fry (53 ind/m2/month) is obtained with a sexratio of 3:1. One will be able to feed the parents with rice, for example As regards the production of fingerlings, the technique of breeding cages can increase very significantly the amount of larvae produced through the frequent harvest larvae as their production.

A

B

E

C

D

F

Figure 132. Live fish storage in hapas or nets. A: Wood frame and net bag; B, C and D: Hapas or cage in net in pond or in channels; E: Basket; F: Wood and mesh holding box.

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These harvests, repeated and complete, are all the more effective as they do not require draining of the pond, nor fishings with the seine, and thus limit the losses of offspring regularly observed at the time of these operations. Moreover, the system with double net reduces the cannibalism exerted by the adults, thus increasing the number of larvae produced by female. To note that cages and hapas can be used to store fish collected during the draining of the ponds of production. Consequently, in fishfarming production, it seems advisable to install parents with the density of 4 ind/m2, of 1.5 to 2 years old, with males slightly larger than the females with a sexratio of 1 male for 3 females. These cages or hapas can be put directly in the water supply channe or other points where they will be protected. They can be used for several ends: ÖÖ Production of fingerlings

ÖÖ Storage of fingerlings collected in the wild

ÖÖ Storage of the associated species after captures in the wild ÖÖ Storage of fish after draining of the ponds.

One will be able to also make use of small nets or others materials for that (Figure 132, p. 144).

III.4. THE OTHER STRUCTURES

There exist other structures like the concrete basins or aquariums to produce fingerlings. However, these structures are rather indicated for large production in commercial-type operations. They require costs and technical much more higher and expensive (Photo V below). The basins in masonry or breeze blocks generally have a elongated shape making it possible to maintain a good circulation water. The aquariums must be of big size (minimum 200 l for tilapia).

Photo V. Concrete basins and aquariums (Ghana) [© Y. Fermon].

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IV. THE STOCKING OF THE PONDS When the pond is filled with water, that it will have been fertilized and that water will have become sufficiently green and that the fingerlings are available, it is now time to introduce them into the ponds. The density of fish, in relation to the species and its behavior is one of the key components of the success of the farming. Then, when the herbivorous fish arrive at a size enabling them to reproduce, one will put some predators to control the reproduction and to limit to possible the presence of a too high number of fry. The fish will not do what you want that they make. They will evolve according to the conditions that you give them. It thus will be necessary to give them optimal conditions for an investment of their metabolic energy in the growth. The optimal density of stocking of a fishpond is the amount of fish at the beginning of the period of production which guarantees to obtain the highest income. The definition of the density of stocking of a pond is one of the most important parameters for the success of a fishfarming. In the fishfarming systems, a stock of fingerlings grows bigger at an almost maximum speed as long as the food and the other environmental conditions are not limiting. When they become it, the reached biomass is called critical charge (CSC). The growth decreases starting from this CSC, but it is not null. The biomass thus continues to increase, until the population reaches the level of biotic capacity or (K). Starting from K, the effects related to the density of the population are such as the growth stop and the biomass remains stable. It is however possible to increase the density of stocking, which makes it possible to increase the yield, as long as the rate of increase in the density of stocking remains higher than the reduction in individual growth rate. But, from the moment when the reduction in growth rate becomes higher than the increase in density, the yield falls, as that appears on Figure 133 below.

Yield per unit area (Y) Growth rate (G)

If the fish are put in ponds with low density and that the natural foods are abundant, they grow bigger with the maximum speed allowed by the temperature. A supplementary feeding contribution is useless at this stage and does not bring anything more because the food is not a limiting factor. On the other hand, when high stock reaches the CSC, the food becomes limiting. The growth thus decreases, except if the management of the farming is intensified. If the production of natural food can be increased by fertilization, Y the maximum growth is started again, until a new CSC is reached on a higher level. At this stage, a complementary food can be necessary to the maintenance of the maximum growth. Then, again, a G G CSC is reached when the quality of food or water quality becomes limiting. Y The density can be used to control the average growth rate of fish and consequently, the duration of the period of farming. As already considering, when the Density of fish density of stocking is increased, the CSC is reached for a less inFigure 133. Diagram on the relationships between the dividual weight and the growth stocking density, the instant growth rate (G) and the beyond the CSC is reduced. The instant yield per surface unit (Y) with (dots) and without average growth on the totality of (plain) complementary feeding. the period of farming is conse-

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quently lower. In a more general way, the individual yield and the growth are respectively positively and conversely correlated with the density. In other words, until a certain threshold, more the density is low, more the growth is fast and more the yield is low. The fishfarming systems in pond selected are polyculture dominated by the tilapia, especially Oreochromis niloticus (or others tilapia). In some places, a catfish was selected like principal species. The group of catfish with Clarias gariepinus, Heterobranchus isopterus and Heterobranchus longifilis is the second great group, the last of these species (H. longifilis) is used only in intensive systems of farming with granulated food. Although very often forgotten, Heterotis niloticus is probably the third fish by order of importance. By using relatively low densities, a better growth rate, a higher final weight but a lower yield can obtained. But with a higher growth rate, the duration of the cycle of farming decreases, which can allow to obtain a higher benefit at the end of the year. Experiments led in Ivory Coast showed that the compromise between the yield and the final average weight is for a density ranging between 4 000 and 7 000 tilapia/ha (Figure 134 below). From now, it is advisable to use a densities of stocking lower than before for the fishfarming of low level of inputs. This density is of 5 000 poissons/ha, that is 0.5 ind/m2. Before, the usual density was generally of 2 ind/m2. ÖÖ The density of tilapia have to be of 0.5 ind/m2.

Yield (kg/ha/year)

Mean weight (g)

The majority of the projects retained and still retain the catfish (often Clarias gariepinus). This technique is very constraining: It is necessary to be able to get, at each beginning of cycle, catfish fry well calibrated to prevent that those do not attack the tilapia in growth in the pond. Moreover, if, for an unspecified reason, the duration of the cycle increase, the catfish, growing faster, will forsake fry of tilapia to attack the large individuals. The value of the production fall down then since the large fish are more expensive than the small ones. If some seasons, the catfish fry are aboundant, they are difficult to find in the wild at other times of the year. In the extensive fields, Clarias gariepinus appeared a poor carnivore, incompetent of reduce the amount of fingerlings. On the other hand, some individuals have a growth so fast that they are able to attack the large tilapia at the end of 4 to 5 months. It is to better retain Hemichromis fasciatus, or another piscivorous Cichlidae with an easiest management. This small carnivore, of size definitely lower than the tilapia, can attack only fry. It is with this type of carnivore that the fastest growths of the tilapia were recorded (Figure 135, p. 148). This gives a new advantage: It makes it possible to quickly obtain a product of large size, appreciated better by the consumer. The eradica600 6000 tion of fry of tilapia (first competitors for the large tilapia for the food re500 5000 source) allow to develop twice better the inputs. Moreover, the presence of carnivores facilitates the control of 400 4000 the populations. It is not then necessary any more to practice tiresome 300 3000 and hazardous fishing to eliminate fry. This does not prevent, once the field controlled by a predator, to ju200 2000 diciously use some catfish put after the beginning of the cycle, and with a 10 1000 density where they will not influence the growth of the tilapia. 0 0 The polyculture with Heterotis ni0.1 0.4 0.7 1 loticus became important at the end Density (ind/m2) of 80s. This species does not seem to induce a reduction in the yield of Figure 134. Yield and average weight of Oreochromis the tilapia, but appears, at contrary, niloticus at the harvest in function of initial density.

Subsistence fishfarming in Africa

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perfectly complementary. One leaves a number very limited breeders of Heterotis (of more than 1 year and half old) to reproduce, one observes the way in which the reproductive breeders take care of its fry and, when those appear sufficiently large to be isolated, they are collected (at the end of 1 to 2 months). In economic terms, the association of Heterotis and tilapia corresponds to a more intensive use of surface. The polyculture with of Cyprinidae is still weak in Africa except with introduced species. One can think that this one can develop with indigenous species. One can thus associate the tilapia as principal species (Oreochromis niloticus when it is present) with a catfish (Heterobranchus isopterus, Clarias spp.), Heterotis niloticus and a predator (Hemichromis fasciatus, Parachanna spp. or Serranochromis spp.) to eliminate undesirable fry, according to a ratio of 0.03 for Heterotis niloticus, 0.04 for Siluriformes, 0.2 piscivorous for each tilapia. For the predator, the proportion must be approximately 13% of the weight of put tilapia. Globally, ten fish of approximately 7/8 cm for a hundred tilapia having reached 6/7 cm are enough. The stocking of predators will be done approximately one month after stocking the pond in tilapia.

Introduction of predator

Reproduction at small size



Growth

 Available food



Growth



Available food

Reproduction at higher size



Growth

Reproduction at small size

Dwarfism

Predation

Good growth

Figure 135. Impact of the presence of a predator (here, Hemichromis fasciatus) in fishponds. On left: Without predator; On right: With predator.

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V. THE FOLLOW-UP OF FISH For proper management, you will need to know on regular occasions how big your fish are and how fast they are growing. For this, a sample of fish from the pond will be measured and weighted. For live fish it is always best to weigh them in clean water, as quickly as possible (Figure 136 below). The total weight of a certain number of fish can be measured. Best is to put a batch in a container or a bag which will be weighed. After counting of fish, there will be then a mean weight by individual. To measure the live weight of relatively large fish such as breeders, one can simply use a satchel or stretcher made for example of canvas slung from two wooden bars. Length measurements are particularly quick and useful for medium to large fish and can be done with far less stress or damage to the fish. The easiest way to measure fish length is to use a fish measuring board. You can make one simply of wood. One fixes a flat ruler graduated in millimetres and centimetres on top of the horizontal board. One also fixes a small plank perpendicularly against which one will bring the rule to thfe level from the zero. One make sure that the board is smooth. A coat of good waterproof varnish is useful. To measure the length of a fish, one places it on the horizontal board, the end of his head against the small vertical plank, therefore on the level zero of the rule. His caudal fin well is extended and one measures the length on the graduated scale. One often uses the total length or the fork length. However, it is better to use the Standard Length (SL) (Appendix 03, paragraph I, p. 207).

Tare

Weighing

Spring

B A simple wooden  fish measuring box  finish with water  proof varnish

Commercial

A Figure 136. Measurement gears. A: Balances and springs; B: Taking a weight; C: Measuring board.

Ruler in mm or cm

C

Subsistence fishfarming in Africa

149

240 220 200

Fresh weight (g)

180 160 146

140 120 100 80 60 40 20 0

0

7

8

9

10 11 12 13 14 15 16 17 18

Total length (cm)

19 20 21 22 23 24 25 20.4

Figure 137. Length - Weight relationships. Length and weight of fish can be related mathematically, and so weight can be estimated from length measurements (Figure 137 above). This relationship varies with the species and its environment. For that, it is necessary: 1. To take a fish sample in the pond. 2. To measure the standard length preferably each individual then, 3. To weigh fish individually. The sample must have a minimal size of 20 individuals, even if statistically a sample of 5 individuals is enough. If the weighing of fish is difficult, it is advisable to use the relation length-weight, in order to consider the individual mean weight of fish. It is enough for this purpose proceeding as follows. To make a follow-up of growth, one will proceed as follows (Appendix 01, p. 189): 1. To take measurements of a fish sample during stocking; 2. For fish of less than 5 cm of LS, there will be twice a week the same manipulation during the first month. Then, the catches of measurements will be able to be spaced, one per week. It is well, as much as possible, to follow the growth over one 3 months duration.

VI. DRAINING AND HARVEST Farmed fish can be harvested in several ways. One can collect all fish only once (complete draining) or one can do it in several times by making intermediate fishings without emptying the pond before draining completely.

VI.1. INTERMEDIATE FISHINGS

This method allows the owner to get fish throughout farming. It can do it with a net, a cast net, traps or handlines. At the same time it can follow the growth of fish. Intermediate fishings should however not be done too early, it should be waited until the fish reached a sufficient size before collecting them for consumption. The size of fish to harvest varies according to the place where is the location. Sometimes, the fish are consumed with size lower than 10 cm SL. For each harvest, it is necessary to remove only a small amount of fish, especially if there is many intermediate fishings. The owner will have each time to note the weight of the fish which it catchs

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from the pond, in order to add them with the production at the time of complete draining. If these fishings are made in a moderated way, they make it possible to collect a total production higher than if one practices only one draining at the end of the cycle. To collect fish, one will be able to use fishing gears (Chapter 09, paragraph I, p. 127).

VI.2. COMPLETE DRAINING A draining is done always early in the morning, in order to be able to work during the hours of freshness. Thus the fish and especially the fry which one will keep will suffer less. The material and necessary tools for draining (shovel, basins, baskets…) will be gathered the evening before. One will be able to store fish not consumed or sold in cages or hapas. The sale of fish will be envisaged either at the edge of the pond and, in this case, one will inform the neighbors, or at the market of the village, so a fast way of transport will then be provided. When the pond is equipped with a monk, collect fish can be done in two manners (Figure 138 below): ÖÖ Inside the pond, just in front of the monk; ÖÖ Outside the pond, after the fish crossed the monk and the pipe discharge. To harvest your fish inside the pond, one will remove the wooden boards from the monk one row at a time. Each time a row is removed of boards from the monk, one will be sure to put the screen back on top to keep the fish from getting out. When the water is partly drained from the pond, one can harvest part of the fish from the water just in front of the monk. (Figure 139, p. 152). When one will be ready to harvest the rest of the fish, one will continue to take out the boards one by one. However, it is necessary to put back the screen each time until the pond is empty. When all of the water is out, the remaining fis can be harvested. First the baby fish have to be collected and then the big fish. Muddy water is bad for baby fish. So, it is better to let a little clean water flow through the pond to keep it from getting too muddy. A number of fish will pass through the monk. One can place a box or baskets in the draining channel outside the pond, at the end of the pipe coming from the monk (Figure 197 below). It will be necessary well to pay attention that the pipe is well inside the box, so that the fish cannot escape. So now we proceeded to harvest fish.

A

B

C

Figure 138. Harvest of the fish. A: Inside after complete draining; B: Outside, with a box; C: Inside, at the catch basin.

Subsistence fishfarming in Africa

151

Basket

m

0 c

20

50

50 cm

 cm

20

Netting

 cm

Harvesting box

Figure 139. Examples of way to collect the fish outside of the pond.

VII.

SUMMARY ÖÖ After fertilization, the steps are: ÖÖ The collect of specimens in the wild or by production of fingerlings of tilapia; ÖÖ The stocking of ponds with tilapia; ÖÖ The growth monitoring; ÖÖ The collect of predators in the wild; ÖÖ The stocking with predators; ÖÖ The monitoring and partial harvest of fish; ÖÖ Then, after several weeks, the draining and the complete harvest of fish. ÖÖ Emphasis on: ÖÖ Fishing methods and precautions to keep fish in good condition and avoid problems and local legislation; ÖÖ The biology of the species and they provide for good production, breeding, feeding, behavior, both for good growth and in the choice of density; ÖÖ The transport of fish and to provide care in order to avoid a loss of fish which may be the complete number of fish.

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Chapter 10

MAINTENANCE AND MANAGEMENT OF THE PONDS As soon the fish are harvested, the cycle is thus ended (Figure 140, p. 154). It remains, however, to see various aspects to ensure a durability of the ponds and, thus, other productions. They are related to: 99 The maintenance of the ponds; 99 The techniques of conservation and transformation of fish; 99 The management of the ponds; 99 The ponds and health.

I. THE MAINTENANCE OF THE PONDS In order to be able to have a correct production and this over several years, it is advisable to ensure a certain number of interventions and to take precautions on various aspects: ¾¾ The diseases of fish, ¾¾ The nutrition of fish, ¾¾ The regular maintenance of the ponds, ¾¾ The maintenance of the ponds between two uses.

I.1. THE DISEASES OF FISH ÖÖ ÖÖ ÖÖ ÖÖ

Fish diseases may cause severe losses on fish farms through: Reduced fish growth and production; Increased vulnerability to predation; Increased susceptibility to low water quality; Increase of death of fish.

While it may be difficult to avoid fish diseases completely, it is better to try to prevent their occurrence rather than to allow them to develop and then attempting to cure them once they start to cause problems In some cases surviving fish are so weakened that effective treatment becomes difficult. However several simple and effective treatments can be used, either for prevention or early control of disease before it becomes too serious. There are several causes of disease that may affect the fish directly or may continue to cause disease problems. Basically, any factor which causes stress or difficulty to the fish decreases its resistance to disease and increases the chance of disease problems occurring. The three main causes of disease are: ÖÖ An inadequat feeding. Nutritional diseases become more frequent as the culture system becomes more intensive and the fish obtain less of their nutrients from natural food organisms. ÖÖ A stress cause by being exposed to an extreme or a toxic condition. ¾Rough ¾ and/or excessive handling, for example when harvesting or sorting/grading; ¾Overcrowding ¾ and/or behavioural stresses, for example in storage or transport; ¾Unsuitable ¾ water temperature; ¾Lack ¾ of dissolved oxygen; ¾Changes ¾ in pH towards extreme values; ¾Presence ¾ of toxic gases such as ammonia or hydrogen sulphide; ¾Pollution ¾ of the water by agricultural or industrial chemicals, sewage effluents, heavy silt loads.

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0

3 months

Assessment Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Duration: 3 months

Selection Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Draining channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas Duration: 6 - 9 months 3 to 6 months

Completion and filling in water

Fish farming Fertilization

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Maintenance and  follow-up of the  ponds

Stocking with tilapia Follow-up  of the fishes

7 - 10 months Duration: 4 to 12 months

Stocking with  predators

End of the cycle 11 - 22 months

Outside composter

Storage of  fishes Duration: 0.5 to 1 month

Draining of the pond  and harvest Sale and\or transformation  of the fish

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Figure 140. Setting of fish pond: 5. End of cycle and start again…

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Subsistence fishfarming in Africa

Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

5. END OF THE CYCLE

3. PONDS, 4. FISH FARMING

ÖÖ An attack of pathogenic organisms, either externally on the skin, gills or fins, or internally in the blood, digestive tract, nervous system… Disease risks become even greater when fish undergo combined stresses, for example handling when the water temperature is below normal or overcrowding in low dissolved oxygen conditions. Other factors on the fish farm may also be responsible for the survival and propagation of disease organisms, making disease control much more difficult such as: 99 The presence of diseased wild fish; 99 The presence of intermediate hosts such as snails and fish-eating birds, necessary for completing the life cycle of the disease organism; 99 The introduction of disease organisms through contaminated inputs such as food, trash fish or processing wastes, for example imported eggs, juveniles, or broodstock, and water from an upstream pond or farm. Disease prevention can be done with just applying good management practices: ÖÖ Ensure good water quality: sufficient supply, with adequate dissolved oxygen concentration and free of pollution. ÖÖ Keep the pond environment healthy: control silt, control plants, keep a healthy balance of phytoplankton and zooplankton, and exchange water if needed. ÖÖ Keep the fish in good condition with control stocking density. Keep different sizes or sexes separate if necessary to control fighting. Care for your fish during storage and transport. ÖÖ Prevent the entry of disease organisms from outside your farm.

ÖÖ Prevent the spread of disease organisms within your farm. If a disease breaks out on the farm, remove dead or dying fish from the ponds as quickly as possible, at least daily, and do not disturb and stress remaining fish excessively. Apart from obvious signs such as dead or dying fish, there are many other symptoms which show that fish are not healthy (Figure 141, p. 156): ¾¾ ¾¾ ¾¾ ¾¾ ¾¾ ¾¾ ¾¾

99 The behaviour of your fish becomes unusual: Swimming weak, lazy, erratic, Floating in water head up, Rubbing against hard object, Flashing and twisting, Darting repeatedly, Crowding and gathering in shallow water or at water inflow, Individual fish isolated from the main group of fish.

¾¾ ¾¾ ¾¾ ¾¾ ¾¾ ¾¾

99 Some physical signs are present on the fish: Gaping mouth, Body: Open sores, leions, bloody areas, loss of scales, bloated belly, abnormal coloration, Gills: pale, eroded, swollen, bloody or brownish, Eyes: cloudy or distended, Fins: folded,eroded, Presence of disease organisms on skill, gills, fins.

It is not easy to identify in a fish pond why fish show signs of bad health. There are two common situations which you should readily recognize: ÖÖ A large part (if not all) of the fish stock show distress or die suddenly, with only some of the above symptoms of disease such as gasping at the surface or gaping mouths: the cause is prior stress (for example rough or poor handling or transport) and/or bad water quality (often low dissolved oxygen) or the presence of a toxic material such as pesticides or other pollution. ÖÖ Only a few fish are dead while some others show distress. Usually a few fish die over a period of several weeks and some of the above symptoms are present. The cause is improper feeding and/or development of some disease organism.

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155

A

B Figure 141. A: Fish piping on surface; B: Dead fish floating on surface.

Most treatments required not easily findable chemicals and which can pose problems of handling and toxicity. One will thus avoid employing any treatment. It will then be advisable to sacrifice sick fish. However, it will be advisable to know if one deals with disease related to pathogenic organisms. When that is possible and if that appears to be essential because of the importance of diseases in a zone, one can carry out an autopsy with, in particular: 1. Search for external parasites; 2. Search for internal parasites; 3. Color and aspect of the liver. There are three major groups of living organisms that may be responsible for fish diseases: (Figure 142 below and Figure 143, p. 157): 99 The viruses. Their detection and identification requires highly specialized laboratory techniques. Control of viral diseases is difficult and requires specialized advice. 99 The bacteria. Bacteria are minute single-cell organisms (I to 12 µm), usually living in colonies. Their detection and identification generally also require special laboratory techniques. The treatment of bacterial diseases such as tail or fin rot and skin ulcers requires experienced, specialized advice. 99 The parasites. Parasites are very small to small organisms made up of one or several cells. They develop either inside or outside the body.

Skin ulcers

Ichthyophthirius (Protozoa)

Leeches (on body) Tail rot Lernaea (Copepods) Dactylogirus (on gill)

Gill rot

A

Bacteria (1 à 12 µm)

B

Saprolegnia (Fungi)

Figure 142. Diseases of fish. A: Bacterial diseases; B: External parasites.

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3. PONDS, 4. FISH FARMING

Infected fish

White  spots

Maturing trophozoïte in skin and  gills (2 days at 25-28°C)

Juveniles free-swimming  in water (tomites: 30 to  40 µm)

Life cycle from 3 to 5 days at 20°C This  disease  may  spread  rapidly  from  one  fish  to  another  through  water  and  pond  bottom  infections  which  makes  disease  control very difficult 

Juveniles  escape from  the cyst

Parasite encysts on pond  bottom and sbdivides into  many juveniles

A Adult trematode:  In gut of water  bird

Metacercariae  in fish eyes

Egg in  water

Miracidium

Cercariae in  water

B

Mature trophozoïte  free-swimming in  water (500 to 1000 µm)

Snail as  intermediate host

Figure 143. Example of life cycles of fish disease factors. A: Ichthyophthirius multifilis – White-spot diseases; B: Diplostomum spathaceum - Diplostomosis.

• Internal fish parasites are very difficult to control. Although their effects can sometimes be easily identified, detection and identification of the parasites themselves usually requires special skills., • External fish parasites are much easier to detect and identify. It is usually possible to eliminate them. ŠŠProtozoa are very small, single-cell parasites, ŠŠFlukes (Monogenea) are very small worms attached by hooks (0.3 to 1 mm), ŠŠLeeches are rather large, segmented worms attached by a sucker on each end (3 to 5 cm), ŠŠCopepods (crustaceans) attached on the fish body with often two elongated egg sacs attached, ŠŠFish lice (Crustacea) have a flat, disc-like body covered by a rounded dorsal carapace (6 to 10 mm), ŠŠWater fungi (water moulds) are made of filaments that usually grow into a cotton-like mass or mat. They can also develop in the gills.

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I.2. THE FEEDING OF THE FISH

In will the majority of the cases, the fish will take most of their food of the small animals and plants which grow in green water (Chapter 08 p. 118). However, it will happen that it is necessary to distribute additional food contributions if the primary production in the ponds is not good and, therefore, if the growth of fish is low. From a point of view of the nutrition, the organic matter includes the protids (proteins), the lipids (fats), the glucids (carbohydrates), as well as substances in proportion relatively low (micronutriments) such as the vitamins and minerals. The requirements in nutrients vary according to the species (Table XXIX below). The diet varies according to species (Appendix 03 p. 207). Many kinds of materials may be used as supplementary feeds for your fish such as: 99 Terrestrial plants: grasses, legumes, leaves and seeds of leguminous shrubs and trees, fruits, vegetables; 99 Aquatic plants: water hyacinth, water lettuce, duckweed; 99 Small terrestrial animals: earthworms, termites, snails; 99 Aquatic animals: worms, tadpoles, frogs, trash fish; 99 Rice: broken, polishings, bran, hulls; 99 Wheat: middlings, bran; 99 Maize: gluten feed, gluten meal; 99 Oil/cakes after extraction of oil from seeds of mustard, coconut, groundnut, African palm, cotton, sunflower, soybean; 99 Sugar cane: molasses, filter-press cake, bagasses; 99 Coffee pulp; 99 Cottonseeds; 99 Brewery wastes and yeast; 99 Kitchen wastes; 99 Slaughterhouse wastes: offals, blood, rumen contents; 99 Silkworm pupae; 99 Manure: chicken droppings, pig manure.

Table XXIX. Levels of various nutrients in different species of fish. Percentage per size class of fish Nutrients

< 0.5 g

0.5 to 10 g

10 to 35 g

> 35 g

Breeders 30

Tilapia Crude proteins

50

35 - 40

30 - 35

25 - 30

Crude lipids

10

10

6 - 10

6

8

Digestible glucids

25

25

25

25

25

Fibers

8

8

8 - 10

8 - 10

8 - 10

> 27

27

29

22 - 24

27

31

Catfish Digestible proteins Common carp Digestible proteins

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If one chooses the use of additional feeding, the products showing the following characteristics will be preferentially selected (Table XXX below): ÖÖ Adequate food value: high percentage of proteins and carbohydrates and low content of fibers; ÖÖ Good acceptance by the fish for which they are intended; ÖÖ Economic reasons: for a given quality, to choose least low cost preferably; ÖÖ Food available during most of the period of growth of fish; ÖÖ Minimal additional costs of transport, handling and treatment; ÖÖ Facility of handling and storage.

Table XXX. Relative value of major feedstuffs as supplementary feed for fish. Content Feedstuff

Water

Crude proteins

Carbohydrates

Fibers

broken

11.3

L

VH

VL

pollshing

10.0

L

VH

L

bran

10.0

L

VH

H VH

Cereals Rice

Wheat

hulls/husk

9.4

VL

H

bran

12.1

H

VH

L

middlings/pollard

10.5

H

VH

L H

Oilcakes Coconut/copra Cotton seed

8.5

H

VH

without hulls

7.8

VH

H

H

complete

7.9

H

H

VH VH

Groundnut/peanuts without hulls

10.0

VH

H

Mustard

9.5

VH

H

L

Palm

10.5

H

VH

H

Sesame

8.0

VH

H

L

Soybean with hulls

11.0

VH

H

L

Sunflower with hulls

7.3

VH

H

VH VH

Other terrestrial vegetables Coffee pulp fresh

11.4

L

VH

Lucerne, leaves

76.0

VL

L

L

Sweet potato, leaves

89.2

VL

VL

VL

Sugar cane

fresh bagasse

45.0

VL

H

VH

molasses

25.0

VL

VH

nil

Aquatic plants Water jacinth (Eichornia crassipes)

91.5

VL

VL

VL

Kangkong (Ipomea aquatica)

92.5

VL

VL

VL

Water lettuce (Pistia spp.)

93.6

VL

VL

VL nil

Animal by-products Blood cattle, fresh

79.6

H

nil

Ruman contents, fresh

57.5

VL

H

H

Very high = VH

30 - 42

40 - 55

20 - 30

High - H

16 - 21

20 - 30

12 - 15

Low = L

7 - 13

7 - 10

5 - 10

<5

<5

<2

Intervalle de valeurs en pourcentage du poids

Very low = VL

Subsistence fishfarming in Africa

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Table XXXI. Example of formula for tilapia and catfish farming. Tilapia / Catfish in fertilized pond

Feedstuffs

Tilapia / Silure in non fertilized pond

Catfish fry (< 5 g)

Fish flour

5

20

55

Soy flour

15

10

7

Cottoon oilcake

25

10

7

Brewery wastes

15

10

7

Bran rice

20

15

5

Wheat

10

10

-

Cocoa or coffee

10

10

-

Maize flour

-

10

5

Calcined bones flour

-

5

4

Palm oil

5

Composition (%) Crude proteins

28.5

29.5

43.3

Crude lipids

8.0

9.0

11.0

To obtain best results, it is better to use simple mixtures of various feedstuffs to provide the fish with the additional proteins and good carbohydrates required. As far as possible, one will have to avoid using a high proportion of fibrous materials to feed the fish. (Table XXXI above). The mix will be made regarding the available feedstuffs for a lowest cost. It is not easy to know which quantity exactly of food to give to fish. The observation of fish allows to have an idea of their needs. To determine the necessary quantities the following factors have to be take into account: ÖÖ The small fish relatively need more food than the large ones. ÖÖ In the presence of an abundant natural food, less additional food is necessary. ÖÖ The quantity necessary of additional food is of as much less important than its quality is improved, ÖÖ Water with high temperature requires a more abundant feeding than water at fresher temperature. The total quantity of supplementary feeding to be given daily to the fish in a particular pond is usually expressed as a percentage of the total weight Table XXXII. Example of quantity of food to give according time per m2 of pond.

160

Table XXXIII. Feeding rate for tilapia in pond related to the size (table of Marek). Size class

Rate in monoculture

Rate in polyculture

5 to 10 g

6.67

5.33

10 to 20 g

5.33

4.00

20 to 50 g

4.60

3.71

50 to 70 g

3.33

2.67

Time

Weight / m2

70 to 100 g

2.82

2.24

1

360

100 to 150 g

2.16

1.76

2

480

150 to 200 g

1.71

1.43

3

720

200 to 300 g

1.48

1.20

4

960

300 to 400 g

1.29

1.03

5

1200

400 to 500 g

1.15

0.93

6

1440

500 to 600 g

1.09

0.87

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or biomass (B), of fish present. This percentage is called the daily feeding rate (DFR). For example, if DFR = 2.5 % of the fish biomass B = 80 kg, it will require 80 x (2.5 / 100) = 2.0 kg of supplementary feed to be distributed daily in the pond. This quantity will change during the growth of fish and thus of the increase in the biomass of fish in the pond (Table XXXII and Table XXXIII, p. 160). If the fish do not eat all distributed food, it is advisable to decrease a little the quantities the next day. Conversely, if the fish quickly eat all distributed food, a little the quantities will have to be increased the next day. To be able well to observe fish, it is easier to feed them at the same time each day, preferably early the morning and in end of the afternoon, when the weather is fresher and this, at the same place. It is easier to feed them in the lower deep part of the pond in order to be able to observe them while they eat. If the quantity of distributed food is too important, part of this one will settle at the bottom of the pond, which will pollute the water of the pond. To facilitate the feeding and the observation, one can manufacture a square or a circle frame of bamboo or light wood and attach it to a stake that to insert in the ground. It is then enough to put the food inside the square or of the circle (Figure 144 below). One will be able better to thus see the quantity of food which settles at the bottom or to touch the bottom with the hand to see food whether settled. There are several occasions on which it is advantageous or even compulsory to stop feeding your fish: 99 When the water temperature is too low or too high (Table XXXIV below); 99 When dissolved oxygen content is limited; 99 On the day you apply manure to the pond; 99 If ever a disease epidemic appears in the pond; 99 When manipulations have to be done in the pond. It will also be necessary to pay attention to storage in the event of need for feeding. Feedstuffs must be stored with special care to prevent excessive deterioration in quality and feed losses. The most Important factors to control are the following: 99 Moisture content of both air and feedstuffs should be maintained as low as possible. 99 Temperature of both air and feedstuffs should be kept as low as possible. At temperatures above 25ºC, the rates of deterioration and loss may rapidly increase. 99 Moulds (fungi) and insects (beetles, moths, weevils, etc.) may cause considerable losses and may contaminate feeds with their metabolic by-products. High temperature and high moisture levels favour their development. 99 Rodents (mice, rats, etc.) and birds Table XXXIV. Examples of stop feeding per species can consume important quantities of in function of the temperature feedstuffs. Their wastes may also contaminate the feeds. Species Range of stop temperature 99 Human theft and indirect damage Mosambic tilapia < 19 and > 35°C to feed stores may also increase other Nil tilapia < 18 and 34°C control problems. Catfish

< 18 and 36°C

Earth mound

A

B

C

Figure 144. Structures to facilitate the feeding. A: Raised pond area; B: Fixed submerged tray; C: Fixed floating frames.

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I.3. DAILY ACTIVITIES OF FOLLOW-UP Although reduced in a case of production fishfarming, certain regular activities must be carried out to ensure a good production of fish (Table XXXV below). At least once per day, the fishfarmer must visit the ponds and check that: ÖÖ The water supply entering each pond is adequate; ÖÖ The dikes are in good state; ÖÖ Water quality is satisfactory, as shown by the behavior to fish and the presence of plankton. The best moment of the day for this visit is early the morning, when the dissolved oxygen contents are likely to become insufficient and that the owner can contribute to preserve the good state of health of fish. If possible, a second visit of the ponds can take place towards the end of the afternoon, in particular during the critical periods, to take care that the fish remain in good health during the night. More detailed controls must be made once per week and in a periodic way on: ÖÖ Channels and dikes of the ponds, for major maintenance or repair, ÖÖ Filters, ÖÖ Compost piles, in order to fill them if necessary. In all circumstances, it is necessary to maintain under control the development of the terrestrial vegetation and to use it for composting. It will also have to be taken care that the ponds remain protected well as that was mentioned before (Chapter 07 p. 73).

Table XXXV. Monitoring. x: following; xx: fuller check or major repair; V: In drained pond only. Items

Monitoring and possible action

Daily

Weekly

Periodically

Main water intake

Clean/repair/adjust

Water supply channel

Clean/repair/adjust

x

-

-

x

xx

Pond inlet

-

Clean/repair/adjust

x

-

xx V

Check/clean

x

-

x

Water level

Check/adjust

x

-

-

Water quality

Color check

x

-

-

Check/repair/protect

x

xx

xx V

Thickness check/quality

-

-

xV

Check/remove

-

x

xx V

Water supply

Filters Pond

Dikes Bottom mud Aquatic plants Terrestrial plants

Check/remove

-

x

xx

Pests

Check/remove

x

-

xx

Fish behavior

Check

x

-

-

Compost piles

Check/refill

-

x

-

Protect

x

-

-

Fish

Theft

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I.4. MAINTENANCE WORK AFTER DRAINING I.4.1. DRYING POND

The drying of a pond is the time that a pond stay without water (period between draining and next water filling). It can be total or partial, for short to long time. The dry setting allow some favorable effects because physicochemical and biological phenomena: ÖÖ Mobilization of nutrients in the soil, ÖÖ Rapid mineralization of organic debris, ÖÖ Destruction of aquatic plants, germs of disease, parasites and predators of some fish. The period of dry setting can be reduced at a few days. A short period is also preferable to avoid the formation of cracks in the dikes and in the bottom of the pond, due to the shrinkage of clays. A light work of the surface bottom of the pond can contribute with the ventilation of the ground and the three points mentioned above. However one should not plow deeply, because that could cause an increase on the unproductive land surface, and an in-depth hiding of the surface layer rich in nutritive elements. A culture (leguminous plants or food crop) can be carried out on the bottom of the pond during a prolonged dry setting. The not collected parts will be then put into the ground before the filling again the pond in water. However, this culture will have to be as short as possible.

I.4.2. CLEARING THE PLATE It is generally at the deepest place of the pond (in front of the monk), that the mud tends to accumulate. It is necessary to remove it so that the fish can, during harvest, havethere the water cleanest possible. This mud is composed of an accumulation of sediments of the surface layer of the bottom of the pond and organic remains. It is thus very rich in nutritive elements and can be used beside the pond as fertilizer for gardenings. It is also possible, in order not to lose these nutritive elements, to distribute this mud on other places of the plate without however leaving too much of it.

I.4.3. REPAIR OF THE DRAINS The drains tend to be filled during the productions. A fast passage according to the layout of the initial network will be enough, but mud will have to be rejected far and not deposited on the edges of these drains.

I.4.4. REPAIR OF THE DIKES At the time of the construction of the ponds a slope inside the pond was respected. During the production a degradation occurs because of the digging of the banks by the population (nests of the tilapia), collapses by compressing during carried out work, a ceaseless erosion due to the waves (in the large ponds). It is then necessary to carry out a banking up of the dikes by contribution of new ground (clay) and to remake the initial slope. If necessary, it will be necessary to stop the burrows dug by small animals in the dikes.

I.4.5. REPAIR OF TH E WATER INLET It often happens that the water inlet was badly envisaged (too short) and that a digging occurs in the dike upstream of the pond plumb with the pipe. A flat rock stone or pile is deposited on the bottom of the pond at the point of fall of the filament of water to break the jet and to reduce degradations by undermining. If not, a repair of the dike is essential with a stone facing to limit the erosion of water..

I.4.6. MAINTENANCE OF THE MONK When there is monks of brick or masonry, it is necessary to check the external rough coat. If a light deterioration is noted, the rough coat should be remade. If the joints of cement are already attacked, it is necessary to rejoint the stones or bricks and to replaster the unit. A defective condition of some small boards, their replacement have to be carried out.

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I.5. FIGHT AGAINST PREDATORS Farmed fish have many enemies and competitors, such as wild fish, frogs, insects and birds, from which they should be protected (Figure 145 opposite). Protection is particularly important while the fish are still very small. Pest control in drained ponds, also called pond disinfection, has several objectives, namely: ÖÖ To kill aquatic animal predators, such as carnivorous fish, juvenile frogs and insects left in the water puddles and in the mud, which would survive and feed on the young fish to be stocked; ÖÖ To eliminate all non-harvested fish, which later would compete with your new stock for space and food, especially if they reproduce without control; ÖÖ To destroy fish parasites and their intermediate hosts, such as snails, and thus help control diseases.

Wild fish

Birds

Snails

Froggs Snakes

Crabs Turtles

Figure 145. Some predators of fish.

Certain disinfection treatments have additional benefits such as improving water and bottom soil quality or increasing the pond fertility. Earthen fish ponds are most easily disinfected after their water has been drained as thoroughly as possible, by gravity for drainable ponds. By keeping the pond dry (preferably in warm, sunny weather). many undesirable will be eliminated. The ultraviolet rays of the sun have a powerful sterilizing effect. Depending on air temperature, it will be necessary keep the pond fully dry from 24 hours (at the minimum) to one month. Some agricultural by-products can also be used to disinfect drained ponds cheaply whenever they are locally available, for example rice bran (400 to 1000 kg/ha), crude sugar molasses (400 to 500 kg/ha) and tobacco dust or tobacco shavings (300 kg/ha). One will just spread the required amount of by-product over the pond bottom. Then, one will flood with 5 to 10 cm of water for 10 to 15 days. It is best not to drain the pond but to fill it up, so as not to lose the fertilizing effect of the organic disinfectant. Before applying tobacco dust or tobacco shavings, it is best to soak the sacks in water overnight. This step will prevent the dust being blown away by wind during spreading on the pond bottom. It is better to avoid the use of chemicals like lime.

I.6. SUMMARY ÖÖ Emphasis on: ÖÖ The daily visits for maintenance; ÖÖ The control of fish behavior and actions to be taken (ventilation, autopsy ...); ÖÖ The nutrition only if necessary; ÖÖ Maintenance of ponds with the cleaning and the fight against predators.

Once this work finished, it is enough to remake to run water in the pond and to fertilize it with animal or vegetable compost, animal manure or vegetable matters like before. Once green water become again, one can stocking again.

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II. THE TECHNIQUES OF CONSERVATION AND OF TRANSFORMATION According to the quantity of harvested fish and their destination (sale or direct consumption), it will be possible to store fish for a later consumption, or to market it, either alive, or fresh or preserved or transformed. If one wishes to keep alive fish, one will be able to put them either in small basins or fish ponds builds with this use, or by using cages or grabbed (Chapter 09, paragraph III.3, p. 142). One will be able to then take when it is wished fresh fish for consumption or the direct sales. Local sale of fresh farmed table fish is the simplest and cheapest way of marketing. Usually people prefer fresh to processed fish. But to ensure good quality and a good price, the fish should be handled properly. Before harvest, fish feeding have to be stop at least one day beforehand. During harvest, the live fish will be handle carefully. If necessary transfer them quickly to a storage facility, for example, to remove any unwanted muddy flavour or to simplify or make more attractive selling arrangements. After harvest: if muddy, the fish have to be rince well in clean water. It is best to kill the fish quickly with minimum stress. As soon as a fish dies, it starts to decompose. This process is mainly caused by the increased activity of bacteria, which rapidly multiply within the fish under favourable conditions of food, temperature and humidity. Bacteria are especially numerous on the gills and in the digestive tract of live fish. It is from there that decomposition will quickly spread to the whole body as soon as a fish dies. As soon as the fish are collected and killed, it is preferable to empty them and remove all the internal organs and blood and/or to remove the gills (or to cut the head). It is necessary to preserve the cleanliness of fish by washing them with clean water. One will avoid posing directly on the ground and one will be able to protect them carefully, for example in cases or bags of plastic to protect them from mud, dust, insects… If one wants to sell it fresh, it should be sold as quickly as possible. Either one collects only the quantity of fish which one thinks of being able to sell the same day, or one will keep them cool, in the shade or covered with sheets of banana tree, of grass… The best is to obtain ice, but it is rarely the case. On the other hand, one will never leave fish died in water because they will rotten quickly. If one must transport them, the best is to avoid the hottest hours of the day and to travel early the morning or even the night. Although it is to better privilege the sale of fish fresh, in some cases, the treatment of fish may be preferable. One will be able either to expose it to high temperature by cooking it, or to lower the water content of fish by drying, salting or smoking (Figure 146, Figure 147 and Figure 148, p. 166). 99 Drying consists in removing the water from the surface and the flesh of prepared fish. 99 Salting consists to remove most of water present in the flesh of fish and to replace it by salt. 99 Smoking consists in removing most of the water contained in the flesh of fish by an exposure to the smoke of wood. When selecting a processing method, it is important to take into account the type of fish to be preserved. Lean fish such as tilapias are much easier to process than oily/greasy fish such as catfish. Large, deep-bodied fish are more difficult to process than small, slender fish. There are several methods to dry or smoke fish, requiring investments and material more or less important. We will not go here into the details. Various techniques can be found in the technical handbooks of FAO. As soon the process on fish is done, it will be important to store the dried or smoked fish properly: ÖÖ By keeping it cool and dry; ÖÖ By packing it tightly to protect it from air moisture (mould) and to delay the onset of rancidity of fish fat;

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165

Hanging from a line  between trees or poles

hanging fish for  drying or smoking

Through the eyes

Hanging from a  rack of poles Through the mouth of  throat

Hook in throat

Split open

Figure 146. Differents methods of natural drying of fish. Hang fish vertically and spread damp cloth over  smoker during uses

Chamber 1

Chamber 2

Firebox

ÖÖ By protect it from insect infestation, for Smoke chamber  example by placing it in with the top  woven baskets lined with covered with iron  rods or metal mesh plastic or strong paper; if you use plastic bags, keep them away from Firebox with a  direct sunlight to avoid perforated metal cover moisture building up inside. It is important to Cut fire door (20 x  25 cm), but keep  check regularly on the the metal piece to  quality of your stored fish close box during  and reprocess it as nesmoking cessary.

Figure 147. Example of smoking method of fish. Barrel or box

ÖÖ Take in mind that: ÖÖ To sell the fish, it must be prepared; Layer fish with salt on top and  bottom and along sides

Figure 148. Example of salting system.

166

Subsistence fishfarming in Africa

ÖÖ The fish can be kept alive or ÖÖ It can be smoked, salted or dried.

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3. PONDS, 4. FISH FARMING

III. THE MANAGEMENT OF PONDS Proper management consists of monitoring the fish ponds regularly, keeping good records and planning ahead for the operation of the farm. On this basis, for example one can decide when to fertilize your ponds.

III.1. FISH STOCKS AND USEFUL INDICES FOR MONITORING It is important to monitor the fish stocks closely. For this it is necessary first to learn about the various indices or parameters which are commonly used to measure and compare the performances of various stocks in fish farms such as their growth, production and survival. The following terms are used to describe the size of a fish stock: 99 Initial fish stock which is the certain number and weight of fish stocked into the pond at the beginning of the production cycle. Two parameters then are: ¾¾ Stocking rate which is the average number or weight of fish per unit area such as 2 fish/ m2, 2 kg fish/m2, or 200 kg/ha; ¾¾ Initial biomass which is the total weight of fish stocked into a specified pond such as 100 kg in Pond X. 99 Fish stock during production cycle which is the certain number and weight of fish present in the pond. They are growing, although some of them may disappear, either escaping from the pond or dying. An important parameter is then: ¾¾ Biomass present which is, on a certain day, the total weight of fish present in a pond. 99 Final fish stock which is the certain number or weight of fish at the end of the production cycle, similarly: ¾¾ Final biomass which is the total weight of fish present at final harvest. Concerning the changes in a fish stock at harvest or over a period of time: ÖÖ Output or crop weight is the total weight of fish harvested from the pond.

ÖÖ Production is the increase in total weight that has taken place during a specified period. It is the difference between the biomass at the end and the biomass at the beginning of the period. For example, for a stocking of 55 kg, and a weight measured after 30 days of 75 kg, 75 - 55 = 20 kg. ÖÖ Yield is the production expressed per unit area. For example if 20 kg were produced in a 500 m2 pond, the yield during the period was 20 / 500 = 0.040 kg/m2 = 4 kg/100 m2 or 400 kg/ha. ÖÖ Production rate is the production expressed per unit of time (day, month, year, etc). For example, if 20 kg were produced in 30 days, the daily production rate would be 20 / 30 = 0.66 kg/day. ÖÖ Equivalent production rate is the yield expressed per unit of time, usually per day or per year = 365 days. It enables to compare productions obtained in various periods. For example 400 kg/ha produced in 30 days are equivalent to (400 x 365) / 30 = 4 866.7 kg/ha/year. It may be also useful to indicate the average daily production rate, which in this case is 4 866.7 / 365 = 13.3 kg/ha/day or 1.33 g/m2/day. ÖÖ Survival rate is the percentage of fish still present in the pond at the end of a period of time. It should be as close as possible to 100 percent. For example, if there were 1200 fish at the beginning of the period and 1 175 fish at the end, the survival rate during that period was [(1 175 x 100) / 1200] = 97.9%; mortality rate was 100 - 97.9 = 2.1%. A stock of fish is made of individuals. One can point out here the measurements taken on the individuals for the follow-up of the pond (Chapter 09 paragraph V, p. 149). ÖÖ The average weight (g) obtained by dividing the biomass (g) by the total number of fish present. ÖÖ Average growth (g), i.e. increase in the average weight during one period of time given. It is about the difference between the average weight at the beginning and the end of the period.

ÖÖ Average growth rate, i.e. the growth (g) expressed per unit of time, generally a day. One speaks then about daily growth rate, obtained by dividing the growth for one period given by the duration of this period into days. It is calculated either for one period determined during the operating cycle, or for the totality of this cycle.

Subsistence fishfarming in Africa

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Example: A pond (312 m²) have been stocking with 680 fish of an initial biomass of 5.6 kg. At the end of the cycle of production (149 days), the harvest was of 43.8 kg for 450 fish. So: Pond production = 43.8 - 5.6 = 38.2 kg Yield = 38.2 / 312 = 12.24 kg/100 m2 Production rate = 38.2 / 149 = 0.26 kg/day Equivalent production rate = (12.24 x 365) / 149 = 30 kg/100 m2/year Survival rate = [(450 x 100) / 680] = 66% Mortality rate = 100 – 66 = 34% Initial average weight of the fish was of 5600 / 680 = 8.2 g, and final average weight of 43800 / 450 = 97.3 g. So, it is: Average growth during the cycle of production = 97.3 – 8.2 = 89.1 g Daily groqth rate = 89.1 / 149 = 0.6 g/day.

III.2. THE EXPECTED YIELDS Yields depend on the species used. However, one can give an estimate of the expected weight per pond, depending on the species. Let us consider a pond of 400 m2 containing Nile tilapia (polyculture with the African catfish Clarias gariepinus), of weight to loading ranging between 5 and 10 g for the two species. At the end of 7 months of extensive farming (fish given up with themselves, without any contribution), one can expect a production of approximately 30 kg (either in the 750 kg/ha/an). For the same duration in a little less extensive (more or less fertilized pond), the annual production will vary from 50 to 100 kg, that is to say the equivalent from 1.2 to 2.5 tonnes/ha/an. That will go up to 10 tonnes/ha/an in farming with a predator, that is to say 150 kg per pond of 400 m2 over 6 months. In polyculture which associates Heterotis niloticus and Heterobranchus isopterus, the juveniles of H. isopterus are introduced with the maximum density of 20 individuals per are into the ponds of production of tilapia. These systems produce yields of about 4 to 15 t/ha/an, according to the level of fertilizer contribution. One can thus obtain 150 kg of fish for a pond of 100 m2 per year, i.e. approximately 12 kg per month for 100 m2 of pond. For a small pond of 200 m2, which is the minimum, one will be able to thus have approximately 24 kg per month of fish, that is to say 0.8 kg per day.

III.3. THE MANAGEMENT OF HARVESTS The management of harvests will depend on the mode of approach. But in most cases, the villagers will have by themselves to regulate this aspect. This management will depend on the quantity of ponds, but it seems adequate to have at least 3 ponds to ensure a quasi monthly harvest with fish of consumable size. If one puts fry in different ponds at different times of the year, one will be able to harvest them at different periods also and, thus, a quantity not too important of fish at the same time. One will be able to fish all the year. If there are 4 ponds and a good supply of fingerlings, it can be stocked in each pond at different month of the year and harvest the pond every 3 to 6 months later according to the size at which fish seem consumables (Table XXXVI, p. 169). Indeed, depending on location, fish of 60 to 80 g will be consumed and a tilapia can reach this size in 3 months. The duration and the time of growth will also depend on the follow-up of growth. By estimating 4 ponds of 400 m2, which can produce up to 50 kg per month by pond, one will be able to produce up to 500 kg per year. In a country where the fish is sold to 5 US$/kg, that will make

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Table XXXVI. Examples of management for 4 ponds. Harvest after 3 months (on left); After 4 months (on right). The color are related to the different steps described in the general frework of setting the ponds. 1st exemple

2nd exemple

Month Pond 1 Pond 2 Pond 3 Pond 4 Harvest

Pond 1 Pond 2 Pond 3 Pond 4 Harvest

1 2 3

1

4

1st year

5 6 7 8

1

3

2

4

3

5

4

6 5

9

7 6

10

8 7

11

9 8

12

10

13 14 15 16 17

2nd year

2

11

9

12

10

13

11

14

12

15 13

18

16 14

19

17 15

20

18 16

21

19

22 23 24

20

17

21

18

22

Stocking fish Maintenance of ponds

Growing Pond not in use

19

Drain and harvest

Subsistence fishfarming in Africa

169

it possible to obtain for the groups the equivalent of 2500 US$ per year, that is to say approximately 200 US$ per month. The distribution of harvests between the beneficiaries will be based according to the type of associations and grouping which was adopted. This can vary according to the countries, the ethnic groups and social structures present in the places where the various projects will be implemented.

III.4. SEVERAL KINDS OF PRODUCTION COSTS An owner of pond must first of all pay the fixed factors of production (capital equipment at lifespan higher than a cycle of production (ground, water, ponds, nets…)) and variables (articles of operation (consumable, labor)). Any expenditure devoted to the exploitation of the fish farm belongs to the costs of this type, and is generally called costs of exploitation. They are thus described as: 99 The fixed operating costs remain the same whatever the amount of fish produced in a given farm. They are related to the fixed factors of production. The most important of these are the depreciation and interest costs associated with the investment and the costs of annual water rights, lease on land, licences and other fixed payments such as interest on loans. 99 The variable operating costs or running costs are those costs that are directly related to the production of the farm. A part from the fixed cost of pond construction (often built through the farmer’s own labour), costs are very low and almost negligible for subsistence farmers. However, it is important to identify the costs as realistically as possible, to avoid wasting time, money or other resources on inefficient or unprofitable operations. As time goes on, long-lasting factors of production such as ponds, buildings, equipment and vehicles wear out. In the short term, they are kept in serviceable condition through maintenance, including the purchase of materials and spares, and labour required for repairs. After a certain number of years Table XXXVII. Useful life of fish farm structures they have to be replaced or reand equipment (in years, assuming correct utilization). novated. This period is called the Structure / equipement Years useful life. Useful life varies, as shown in Table XXXVII (opposite). Pond, earthen 30 Some factors such as buildings Channels, earthen 20 and ponds have a very long useHard wood, treated 10 ful life, while other factors such as wheelbarrows or nets may wear Masonry 20 out within only a few years. Pond structures Concrete 20

Buildings

170

PVC pipes

10

Reinforced, concrete pipes

20

Wood / thatch roof

4

Sundried clay bricks

6

Fired bricks or concrete blocks

20

Boat wooden

8

Fence, wire / treated wooden posts

10

Fishing net

5

Hapas

2

Cast nets, dip nets

2

Wheelbarrow

3

Workshop tools (saw, hammer…)

5

Pick, shovel, axe

2

Buckets, barrel

1

Subsistence fishfarming in Africa

III.5. RECORD KEEPING AND ACCOUNTING Fish farmers need only keep simple records, which should enable them to know, month by month: 99The total amount of money spent on fish farming and per each pond; 99The total number (and weight) of fish stocking initially; 99The total number (and weight) of fish harvested; 99Number of fish given either to family for consumption or in exchange of casual labour;

5. END OF THE CYCLE

3. PONDS, 4. FISH FARMING

99 The total number (and weight) of dead fish; 99 The total number (and if possible weight) of any fish sold for cash (cash income) and/or bartered for other commodities (equivalent value as income). At the end of the year, the above records will provide information on: ÖÖ The total value of the fish given away; ÖÖ The total value of all fish harvested; ÖÖ The amount gained (net profit) or lost (net loss) through fish farming. A simple form can be used day by day to record for one month all activities around the fish farm, every amount of money spent and all the details of fish production (Appendix 01, p. 189). This is called the daily record form. You may prepare a form similar to the example below in a small school copybook, using two facing pages per form. Any activity, such as work done on the fish farm and items of equipment purchased for it, should be immediately noted down together with such relevant data as money spent, number of fish harvested, and number of fish given or sold. It is important to note these details as soon as they are available. At the end of the month, one will just have to sum the different columns to get the monthly totals. In the same way, one will be able with the end of the year, by making the total of the months, to make an annual statement of account.

III.6. THE FORMATION In order to promote and to ensure the continuity of the project correctly, trainings are necessary for the beneficiaries and future operators of the ponds. The topics approached will be: ÖÖ Importance of fish in the food The animal proteins are essential for a good growth of the children as well as the health of the parents. ÖÖ Importance of the rivers: water and health Water is one of the major fields for the development of the human diseases. Several parasites and diseases pass through the water and the lack of hygiene: malaria, cholera, schistosomiasis, to name just a few of them. We will return in the next chapter on health and the ponds. One will not detail here these two topics which are well developed in several books. ÖÖ How to build the ponds One will be able to take the various stages listed in this handbook.

IV. PONDS AND HEALTH Water being the field in which several parasites and vectors of serious diseases pass through or come from. The ponds being water points, it is appropriate to take care of certain rules to limit the problems of disease and health. A mosquito species and several species of freshwater molluscs transmit diseases can be fatal. It is malaria (mosquito) and schistosomiasis (snail). If plants or grasses are too dense on the edges of ponds or in them and in the enclosure, snails and mosquitoes can live and proliferate very easily. Thereforeit will be necessary to periodically remove plants that are there and mow the dikes. Herbs edges should not hang in the water so that fish can effectively eliminate insects or others animals (Figure 149 and Figure 151, p. 172). It is strongly advised not to use the ponds or enclosures as toilets (Figure 150, p. 172). It is to better use a latrine if it is present or to build one to at least 10 m of any edge of the ponds or enclosure and source of water supply. If one is taken of a pressing need during work close to the ponds or the enclosures, of the river which feeds them, of the supply channel or the inlet, a distance of at least 10 m is the minimum to satisfy this need. In the same way, it will be necessary to avoid making its needs on a heap for compost or in the vicinity. A pond is not either a place with a water for domestic use, like drink or washing. It is necessary to transmit to the people having access to the infrastructures these minimal rules of hygiene.

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Figure 149. Mosquito and snail.

Figure 151. Cleaning of the dikes.

yes

m

10 

m

10  yes

no

no no

10 m

no yes

Figure 150. Several human behavior to avoid nearby the ponds.

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Subsistence fishfarming in Africa

General summary All the steps to achieve the production of fish for subsistence is shown in the diagram next page. The fishfarming system choose is this of production, semi-intensive, of self-consumption to artisanal, using polyculture rather than monoculture that request external food input and a more important follow-up if one want an interesting production.

The evaluation of the ecosystem in all its components, human beings included, is of a major importance in order to see which are the actions to propose to ensure a better “wellbeing”, mainly of food safety but also of health and water and sanitation. Preferably, two specialists will be necessary with priority for the biological aspects. The whole of collected information will allow: ÖÖ To know the statement of the zone where the intervention must take place; ÖÖ To know the available resources usable and their current use; ÖÖ To know the communities and social structures.

The goal being to have the elements to propose a solution allowing a good appropriation of the project by the populations, if the various components make it possible to affirm that fishfarming is a solution for the zone considered.

The source of fish to be used and the drainage basin where the action is undertaken are of highest importance, this, because of the risks incurred by the introduction of fish and the national and international legislative aspects concerning the biodiversity It is not either because a species was already introduced into the zone of intervention, that it should necessarily be used.

The choice of the village must take into account: ÖÖ Vulnerability of the population; ÖÖ Logistics; ÖÖ Water resources; ÖÖ Motivation of the villagers. Subsistence fishfarming in Africa

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0

3 months

Assessment Socio-economy Ethnology

Environnemental Ecology - Ichthyology

Villages selection

Sites selection

Duration: 3 months

Selection Ponds

Laying out plan

Purchases of the  equipment Cleaning of the site Staking out the pond

Time

Water supply channel

Ponds inlet Building of the dikes Ponds outlet

Draining channel Pond bottom drain laying out Purchases of  fishing nets Other structures laying out

Building of cages  or hapas Duration: 6 - 9 months 3 to 6 months

Completion and filling in water

Fish farming Fertilization

« Green water »

61/4 - 91/4 months

Collection in natural  water of predators

Duration: 4 to 12 months

Stocking with tilapia

Stocking with  predators

End of the cycle Storage of  fishes Duration: 0.5 to 1 month

174

Maintenance and  follow-up of the  ponds Follow-up  of the fishes

7 - 10 months

11 - 22 months

Outside composter

Subsistence fishfarming in Africa

Draining of the pond  and harvest Sale and\or transformation  of the fish

Intermediate harvest  of fishes Maintenance and  repair of ponds after  draining

Resumption of a cycle

Collection in natural  water or production of  juvenils of tilapia

The site selection is the most important step for a fish pond. It have to take into account: ÖÖ The water: quantity and quality; ÖÖ The soil: impermeable; ÖÖ The topography: Weak slope and zone of emergence of sources.

The choice will go to diversion ponds supplied with water by gravity. rectangular, arranged en parallel, of a size of 100 to 400 m2.

Emphasis on: ÖÖ The cleaning of the site that must be done well; ÖÖ The picketing which must be precise for the slopes; ÖÖ The control and management of the water by channels; ÖÖ The importance of dykes, their strength and their size and although compacted; ÖÖ The choice of a monk for draining ponds; ÖÖ The total isolation of the ponds from the outside for better control; ÖÖ The soil conservation upstream.

ÖÖ For the fertilisation, the preparation of aerobic and anaerobic compost is important. ÖÖ The expectation of a « green water » indicate that the pond is ready for ensemensement.

After fertilization, the steps are: ÖÖ The collect of specimens in the wild or by production of fingerlings of tilapia; ÖÖ The stocking of ponds with tilapia; ÖÖ The growth monitoring; ÖÖ The collect of predators in the wild; ÖÖ The stocking with predators; ÖÖ The monitoring and partial harvest of fish; ÖÖ Then, after several weeks, the draining and the complete harvest of fish.

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African freshwater fish species are numerous and many may be used in fishfarming. The choice of the species will be done regarding the geographic location of the ponds (ichthyoregions). However, in case of subsistence, one will choose: ÖÖ A tilapia for the main production. Strong fish, highly plastic and adaptable to environmental conditions with elaborated parental care, which are opportunistic about feeding, with: ÖÖ A piscivorous species which will be the predator for the reproduction control of tilapia; ÖÖ One will also used other species in the pond as omnivorous and/or herbivorous species. For the predator, the proportion must be approximately 13 % of the weight of put tilapia. Globally, ten fish of approximately 7/8 cm for a hundred tilapia having reached 6/7 cm are enough. The stocking of predators will be done approximately one month after stocking the pond in tilapia. The density of tilapia have to be of 0.5 ind/m2

One of the main principles will be to use only non-destructive gear for the local wildlife. Care should be taken to respect the laws relating to fishing. Where appropriate, permits have to be requested from the local authorities.

Emphasis on: ÖÖ Fishing methods and precautions to keep fish in good condition and avoid problems and local legislation; ÖÖ The biology of the species and they provide for good production, breeding, feeding, behavior, both for good growth and in the choice of density; ÖÖ The transport of fish and to provide care in order to avoid a loss of fish which may be the complete number of fish.

To insure a good production, emphasis on: ÖÖ The daily visits for maintenance; ÖÖ The following of the fish; ÖÖ The control of fish behavior and actions to be taken (ventilation, autopsy…); ÖÖ The complementary nutrition only if necessary; ÖÖ Maintenance of ponds with the cleaning and the fight against predators.

ÖÖ The fish can be kept alive. ÖÖ To sell the fish, it must be prepared. If it is not sell fresh, it can be smoked, salted or dried.

We thus have a master plan of a system allowing to produce consumabl) fishes in the shortest possible time and at a lower cost to compensate a lack of animal proteins.

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References Quoted here are only a few references. This list is not, of course, exhausitive. The reader may also find on the website of the FAO (www.fao.org) various documents relating to fisheries and aquaculture. Arrignon J., 1993. Aménagement piscicole des eaux douces, 4ème édition. Technique & documentation - Lavoisier - Paris. 631 p. Bard J., de Kimpe P., Lemasson J. & Lessent P., 1974. Manuel de pisciculture tropicale, CTFT, PARIS. Billard R. (ed), 1980. La pisciculture en étang, Paris, France : INRA, 434 p. Coche A.G. & Van der Wal H., 1983. Méthode simple pour l’aquaculture Pisciculture continentale : l’EAU. FAO collection formation, 1 volumes 112 p. Délincé G., 1992. The ecology of the fish pond ecosystem with special reference to Africa. Kluwer Academic (Publ.), Dordrecht, Netherlands : 230 p. Egna H.S. & Boyd C.E., 1997. Dynamics of pond aquaculture, Boca Raton, USA : CRC Press, 437 p. FAO, 1997. Review of the state of world aquaculture. FAO Fisheries Circular. N°886, Rev. 1. Rome, Italy. FAO Inland water resources and aquaculture service, Fishery Resources Division. FAO, 2000. Simple methods for aquaculture. FAO Training Series. FAO, 2006. Aquaculture production 1986-1992. FAO/FIDI/C815 (Rev. 6), 216 p. FAO, 2007. Situation mondiale des pêches et de l’aquaculture. (SOFIA). Froese, R. and D. Pauly. (Eds). 2008. FishBase. World Wide Web electronic publication. www.fishbase.org, version (06/2008) Jauncey K. & Ross B., 1982. A guide to tilapia feeds and feeding. Institute of Aquaculture, University of Stirling, Scotland, 111 p. Lazard J., 1990. L’élevage du tilapia en Afrique. Données techniques sur sa pisciculture en étang. p. 5-22. In : Méthodes artisanales d’aquaculture du tilapia en Afrique, CTFT-CIRAD, 82 p. Lazard J. & Legendre M., 1994. La pisciculture africaine : enjeux et problèmes de recherche. Cahiers Agricultures, 3 : 83-92. Lazard J., Morissens P. & Parrel P., 1990. La pisciculture artisanale du tilapia en Afrique : analyse de différents systèmes d’élevage et de leur niveau de développement. p. 67-82. In : Méthodes artisanales d’aquaculture du tilapia en Afrique, CTFT-CIRAD, 82 p. Lazard J., Morissens P., Parrel P., Aglinglo C., Ali I. & Roche P., 1990. Méthodes artisanales d’aquaculture du tilapia en Afrique, Nogent sur Marne, France : CTFT-CIRAD, 82 p.

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Legendre M. & Jalabert B., 1988. Physiologie de la reproduction. In : C. Lévêque, M.N. Bruton & G.W. Ssentongo (eds). Biologie et écologie des poissons africains d’eau douce. ORSTOM, Travaux et Documents, 216 : 153-187. Oswald M., 1996. Les aménagements piscicoles du Centre-Ouest de la Côte d’Ivoire. p 383-400 In LavigneDelville P. et Boucher L., 1996. Les bas-fonds en Afrique Tropicale Humide, GRET-CTA Coop. Française. 413 p. Oswald M., Glasser F. & Sanchez F., 1997. Reconsidering rural fishfarming development in Africa. p 499-511 vol II In Tilapia Aquaculture, Proceedings from the Fourth International Symposium on Tilapia in Aquaculture Orlando (Floride- USA, ed Fitzsimmons K. Nraes, New York, USA. Otémé J. Z., Hem S. & Legendre M., 1996. Nouvelles espèces de poissons chats pour le développement de la pisciculture africaine. In : M. Legendre & J. P. Proteau (eds). The biology and culture of catfishes. Aquat. Living Resour., 9, Hors série, 207-217. Paugy P. & Lévêque D., 2006. Les poissons des eaux continentales africaines. Diversité, écologie, utilisation par l’homme. 2nd édition. IRD. 521 p. Pouomogne V., 1998. Pisciculture en milieu tropical africain : comment produire du poisson à coût modéré (des exemples du Cameroun). Presse universitaire d’Afrique, Yaoundé . 235 p. Pullin R.S.V. & Lowe-McConnell R. H., 1982. The Biology and Culture of tilapia. Proceedings of the International Conference Held 2-5 September 1980 at the Study and Conference Center of the Rockefeller Foundation, Bellagio, Italy, Sponsored by the International Center for Living Aquatic Resources Management, Manila . Pullin R.S.V., Lazard J., Legendre M., Amonkothias J.B. & Pauly D., 1996. Le troisième symposium international sur le tilapia en aquaculture, Manila, Philippines : ICLARM/CIRAD-EMVT/ORSTOM/ CRO. Proceedings of the international symposium on tilapia in aquaculture, 630 pp. Sclumberger O., 1997. Mémento de pisciculture d’étangs. 3ème édition, CEMAGREF, France, 238 p. Wilson R. P. & Moreau Y., 1996. Nutrien requirements of catfishes (Siluroidei). In : M. Legendre & J. P. Proteau (eds). The biology and culture of catfishes. Aquat. Living Resour., 9, Hors série, 103-111. Wolfarth G. W. & Hulata G. I., 1981. Applied genetics of tilapias. ICLARM Studies and Reviews, 6, 26 p.

Useful web sites: www.fao.org www.fishbase.org www.ird.fr/poissons-afrique/faunafri/

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Glossary A

B

Abiotic: Physical factor that influences the development and / or survival of an organism.

Bacteria: Very small unicellular organism growing in colonies often large and unable to produce components of carbon through photosynthesis; mainly responsible of rotting vegetable matter and dead animals.

Abundance: Quantitative parameter used to describe a population. The enumeration of a plant or animal population, is generally impossible, hence the use of indicators. By extension, abundance means a number of individuals reported to a unit of time or area, within a given population, recruitment, stock, reported to a unit of time or area. Amino acid: Class of organic components containing carbon, hydrogen and oxygen, associated in large numbers, they are proteins, some of them play an essential role in fish production. Aerobic: Condition or process in which gaseous oxygen is present or necessary. Aerobic organisms obtain their energy for growth of aerobic respiration. Anaerobic: Sayd for conditions or processes where gas oxygen is not present or are not necessary. Anoxic: Characterized by the absence of oxygen. In a anoxic environment, the maintenance of aerobic respiration is impossible, consequently, the life is limited to the presence of organizations whose metabolism is ensured by other mechanisms (fermentation, anaerobic breathing like the sulfatoreduction, bacterial photosynthesis…). Aquaculture: Commonly termed ‘fish farming’ but broadly the commercial growing of marine or freshwater animals and plants in water. The farming of aquatic organisms, including fish, mollusks and aquatic plants, i.e., some form of intervention in the rearing process, such as stocking, feeding, protection from predators, fertilizing of water, etc. Farming implies individual or corporate ownership of the farmed organisms. Aufwuchs: German term indicating the layer of algae adhering on rocks.

Benchmark: see Point, reference Benthos: Groups of vegetable and animals organisms in or on the surface layer of the bottom of a pond. Associated term: benthic. Opposite: pelagos. Bicarbonates: Acid salts of carbonic acid (see carbonate) solution in water, they contain the ion HCO3 as calcium bicarbonate Ca(HCO3)2 for example. Bioaccumulation: Catch of substances - e.g. heavy metals or chlorinated hydrocarbons - resulting in high concentrations of these substances in aquatic organisms. Biocenose: Group plants and animal forming a natural community, which is determined by the environment or the local ecosystem. Biodiversity: Variation among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part: this includes diversity within species, between species and ecosystem. Bioethics: Part of morality concerning research on life and its uses. Biomass: (a) Total live weight of a group (or stock) of living organisms (e.g. fish, plankton) or of a definite part of this group (e.g. breeders) present in a water surface, at a given time. [Syn.: stock present]. (b) Quantitative estimate of the mass of the organisms constituting whole or part of a population, or another unit given, or contained in a surface given for a given period. Expressed in terms of volume, mass (live weight, dead weight, dry weight or ashesoff weight), or of energy (joules, calories). [Syn.: charge].

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Biotic: In relation to the life and the living matter. Biotope: Zone or habitat of a particular type, defined by the organisms (plants, animals, micro-organisms) which live typically there, e.g meadow, wood, etc; or, with more small scales, a microhabitat. Breeders or brood fish: Adult animal being used to ensure the reproduction. Broodstock: (Stock of) Stock of fish intended for the reproduction, preferably being the subject of a special management in distinct ponds.

C Calcium carbonate limestone or Limestone: Natural rock made up mainly of carbonate calcium CaCO3. Carbohydrate: Composed organic constituted of carbon, hydrogen and oxygen, such as sugars, starch and the cellulose; The energy food generally least expensive, in particular for omnivorous and herbivorous fish. Carbonate: Carbon salt of dioxide, a compound formed of carbonic gas (CO2) in contact with water; for example calcium carbonate, CaCO3 . Cellulose: Organic component which constitutes the essential part of the solid structure of the plants; it is also present in the animal body. Charge: Level at which the water is kept or may be high, allowing for example to flow to lower levels or browse pipes. Colloid: Particle of very small dimension (from 0.5 to 1 micron), either mineral (for example colloidal clay), or organics (for example humus). Conductivity: Measuring the concentration of ions or salts in water in direct relation to the facility with which it conducts electricity. Generally water with high conductivity has a good buffering capacity. It varies with temperature and is expressed in Siemens (S) per meter at 25°C. Conflict of use: Emerging conflict between different users of the same environment which may have the same interests or competitors. Contour line: (a) Imaginary line connecting all the points of the identical level of altitude. (b) Line which joint all the of the same points dimensions on a plan or a chart; it repre-

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sents the course of a level line such as it exists on the ground. Cyst: (a) Phase of very resistant, not-mobile, deshydrated, inactive for free or parasitic organisms, in response to unfavourable environmental conditions. (b) Not-alive membrane surrounding a cell or a group of cells.

D Demersal: Animal living near the bottom but not permanently. Dimension or elevation: Vertical or height distance above a “horizontal” plane of given reference; See Elevation/level and Level/ Reference plan. Digestibility: Relative speed and degree to which a food is digested and absorbed.

E Ecology: Connect sciences concerned with the relations existing between organisms and their environment. Ecosystem: Set (or system) with natural structures and distincts relations which link biotic communities (of plants and animals) to one another and to their abiotic environment. The study of an ecosystem provides the methodological basis for a synthesis of the complex relationships between organisms and their environment. Elevation or level: General terms indicating the vertical distance or height above a reference plan, such as the mean level of the seas (see altitude) or an arbitrarily selected horizontal plan (see dimension); calculated according to topographic data. Embankment: (a) Zone of which it is necessary to raise the level of the ground to a necessary height while bringing ground. (b) Ground itself thus brought back. Endemic: Specific or indigenous in an area. Qualify disease-causing agents and diseases which, at all times, are present or generally prévalents in a population or a geographical area. Energy: In aquaculture: Usually relate to the food needs for the aquatic organisms, expressed by a quantity of joules/calories per day necessary to ensure the essential processes of life, i.e. the growth and the reproduction.

Equidistance of the level lines: Difference in rise between two close level lines. Ethology: Animal behavior science. Eutrophic: Rich in nutrients, phosynthetic productive and often deficient in oxygen under warm weather. Eutrophication: The enrichment of a water body in nutritive elements, in a natural or artificial way, characterized by wide planktonique blooms and a subsequent reduction in the dissolved oxygen content. Extrusion: Process of transformation of food material is subjected for a very short time (20 to 60 s) at high temperatures (100 to 200°C) at high pressures (50 to 150 bars), and a very intense shear .

F Fatty-acid: Formed lipid of a more or less long hydrocarbon chain comprising a carboxyl group (-COOH) at an end and a methyl group (-CH3) at the other end. Fecundity: In general, potential reproductive capacity of an organism or population, expressed by the number of eggs (or offspring) produced during each reproductive cycle.

Relative fecundity: Number of eggs per unit fresh weight.



Absolute fecundity: Total number of eggs in a female.

Feedingstuff, supplementary: Food distributed in addition to food presents naturally. Feedingstuff, composed: Food with several ingredients of vegetable or animal origin in their natural, fresh or preserved state, or of derivative products of their industrial transformation, or of organic or inorganic substances, containing or not additives, intended for an oral food in the shape of a complete feedingstuff. Fermentation: The anaerobic degradation of organic substances under enzymatic control. Fingerling: Term without rigorous definition; says for young fish starting from advanced fry until the one year age starting from the hatching (independently of the size). [Syn.: juvenile]. Food chain: Simplistic concept referring to the sequential series of organisms, pertaining to successive trophic levels of a commu-

nity, through which energy is transferred by food way. Energy enters the food chain by the fixation by the primary producers (green plants for the major part). It passes then to the herbivores (primary consumers) then to the carnivores (secondaries and tertiary consumers). The nutritive elements are then recycled towards the primary production by the detritivores. Fry: A young fish at the post-larval stage. May include all fish stages from hatching to fingerling. An advanced fry is any young fish from the start of exogenous feeding after the yolk is absorbed while a sac fry is from hatching to yolk sac absorption.

G Gauge: Model of wood being used to give the wanted form, for example with a channel or a dike. Gamete: Reproductive cell of a male or female living organism. Gene: ÉlémentBasic element of the genetic inheritance contained in the chromosomes. Genetics: Science for the purpose of studying issues concerning the transmission of traits from parents to offspring in living beings. Genotype: Genetic structure of an organism at the locus or loci controlling a given phenotype. An organism is homozygote or heterozygote at each of the loci. Gonado-somatic ratio: Ratio of the weight of the gonades to the total live weight (or of the total live weight to the weight of the gonades), usually expressed like a percentage.

H Halieutic: Science of the exploitation of the aquatic alive resources. Herbivore: Animal which feed mainly on plants. Hormone: Chemical substance produced in part of an organism and generally conveyed by blood in another part of this organism, where it has a specific effect. Humus: Decomposed organic matter present in organic manures, composts or grounds, in which the majority of the nutritive elements are available for fertilization. Hybridization: Fecundation of a female of a species by the male of a different species.

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Hydraulics: Relating to water, the action or the energy utilization related to its movements.

I Ichtyology: The study of fish. Ichtyophagous: Animal feeding mainly on fish. [Syn.: piscivorous]. Indigenous: Native of a country or a place. [Syn.: native]. Irrigation sluice: Work derivation placed on a feeder canal to divert its flow into two (type in T) or in three (type in X) parts, or to increase the water level in a section of the channel, or to control the water supply with height of the water supply of a pond.

J Juvenile: Stage of the young organism before the adult state. [Syn.: fingerling].

K L Larva, larvae: Specific stage to various animals, which is between the time of hatching and the passage at the juvenile/adult form by metamorphosis. Level: see Elevation. Level or reference plan: Level or plan used on several occasions during a particular topographical survey and by report to which the raised lines or points are defined. Levelling: Operation consisting in measuring differences in level in various points in the ground with topographical survey. Life cycle: The sequence of the stages of the development of an individual, since the stage egg until death. Line of saturation: Upper limit of the wetland in an earthen dike partially submerged. Line of sight: Imaginary line from the eye of the observer and directed towards a fixed point, it is always a straight line, also called «line of sight.» Limnology: The study of the lakes, ponds and other plans of stagnant fresh water and their biotic associations. Lipid: One of the main categories of organic

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components (fats and similar substances) largely present in the living organisms; the lipids have two principal functions: energy source and source of certain food components (fatty-acids) essential to the growth and survival.

M Macrophagous: Living organism which feeds on preys having a size larger than that of its mouth. Opposite: microphagous. Macrophyte: Relatively large vascular plant by comparison with the microscopic phytoplankton and the filamentous algae. The basic structure of a aquatic macrophyte is visible with the eye. Maturation: Process of evolution of the gonades towards maturity. Metamorphosis: All changes characterizing the passage of the larval state in a juvenile or adult state for some animals. These changes concern at the same time the form and physiology and is often accompanied by a change of the type of habitat. Mesocosme: Ecosystem isolated in a more or less large enclosure from a volume from water from one to 10 000 m3. Mainly used for the production of alive preys in earthenware jars, basins, pockets plastic, ponds and enclosure. Metabolism: Physical and chemical processes by which the food is transformed into complex matter, the complex substances are decomposed into simple substances and energy which is available for the organism. Milt: Mass genital products. Said also for the sperm of fish. Monoculture: Farming or culture of only one species of organisms at the same time. Mulch: Made non-dense cover organic residues (for example cut grass, straw, sheets) which one spreads on the surface of the ground, mainly to preserve moisture and to prevent bad grasses from pushing. Mulching: Placement of a layer of vegetable matter, in order to protect young plantations (see Mulch).

N Nekton: Animal whose swim actively in a pond;

Capable of a constant and directed mobility, such as for example the insects and fish. Niche: Ecological role of a species in a community; conceptualized as the multidimensional space whose coordinates are the various parameters representing the condition of existence of the species and to which this one is limited by the presence of competitors species. Used sometimes improperly like the equivalent of microhabitat, referring to the physical space occupied by a species.

Food niche: Role of a fish in a system of farming with regard to the consumption of food.



Ecological niche: Concept of the space occupied by a species which includes not only physical space but also the functional part played by the species. A given species can occupy various niches at different stages of its development.

Nitrate: Final product of the aerobic stabilization of organic nitrogen; Its presence in water is indicative of an organic enrichment of agricultural or industrial origin. Often used as manure in culture of pond. Nitrite: First stage in the oxidation of the ammonium excreted by the aquatic organisms as final product of metabolic degradation. The nitrite inhibits the fixing of oxygen by hemoglobin and becomes thus toxic for fish. The shellfish are less affected because haemocyanin only is partially inhibited. For a given concentration, the nitrite is however more toxic in freshwater than in marine or brackish water. Nitrogenize: Gas element, without odor which constitutes 78% of the terrestrial atmosphere; Present in all living tissue. In gas form, it is almost inert. Nitrogen, ammoniacal: Special term referring to the total weight of nitrogen in ionized form NH4+. Nursery: Protected place for the rearing of young after metamorphosis in the hatchery and conducted before passage from the external environment. Nycthemeral: Succession of the day and the night of 24 hours which rhythm periodic variation of the physiology of the plants and the animals.

Nutrition: All processes by which an animal (or a plant) absorbs and uses the nutritive food or elements; The act or the process by which the organism is feed.

O Oligotrophic: Qualify an environment where the concentration in nutritive elements (= nutrients) is low. Omnivore: Animal which feed at the same time on vegetable and animal matters. Ontogeny: The early life history of an organism, i.e., the subsequent stages it passes from the zygote to the mature adult. Associated term: ontogenetic. Oxidation: Chemical reaction by which, for example, there is an oxygen contribution.

P Parthenogenesis: Reproduction from a female gamete, without fertilization by a male gamete (e.g. at the rotifers). Pelagos: It is the whole of the aquatic organisms which occupy a “water column”. It thus includes the nekton and the plankton. Associated term: pelagic. Opposite: benthos. Perennial: It is said terrestrial vegetation which growths and survives more than one year and which has usually leaves all the year. Periphyton: Associated Microalgues and micro-organisms living attached to any immersed surface. pH: Coefficient used to characterize the activity of the hydrogen ions in a solution or a soil. The pH of pure water is equal to 7 and characterizes a neutral solution. A solution having a pH lower than 7 is known as acid, while a solution with pH higher than 7 is known as alkaline. Phenotype: Physical or external appearance of an organism in contrast with its genetic constitution. Characters of an individual which can be measured and observed. Photoperiod: Period lit, naturally or artificially, and considered from the point of view of the biological phenomena associated with the light.

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Photosynthesis: (a) Process by which the green plants containing chlorophyl transform solar energy into chemical energy, by producing organic matters starting from minerals. (b) Mainly production of composed of carbon starting from carbonic gas CO2 and water, with oxygen release. Phylogeny: Characterize the evolutionary history of the groups of living organisms, in opposition to ontogeny which characterizes the history of the development of the individual. Associated term: phylogenetic. Phytobenthos: Benthic flora. Phytoplankton: Unicellular algae living in suspension in the water mass. Vegetable component of the plankton. Piscivorous: Animal feeding mainly on fish. [Syn.: ichthyophagous]. Plan: Imaginary plane surface; any straight line connecting two unspecified points of a plan is located entirely in this plan. Plankton: All organisms of very small size, either plants (phytoplankton), or animals (zooplankton), which live in suspension in water. Planktivorous: Animal feeding on phyto- and/or of zooplankton. Plasticity: (a) Capacity which has a soil to become deformed without breaking and to remain deformed even when the deforming force does not act any more. (b) Ability of a trait in an organism to adapt to a given environment. Point, lost: Temporary topographic point of reference which one carries out the survey between two definite points; It is not used any more when the statements necessary were made.

184

of speed appearing when water moves through a pipe or any other hydraulic work. Probiotic: All the bacteria, yeasts or algae added to some food products and which help with the digestion of fibers, stimulate the immune system and prevent or treat gastro-enteritis. Protein: Composed organic whose molecule is of important size and of which the structure complex, made by one or more chains of amino-acids; essential to the organism and the functioning of all the living organisms; The food proteins are essential for all the animals, playing a part of reconstituting tissue or energy source. Protozoa: Very small unicellular animal organisms, living sometimes in colonies.

Q R Raceway: Basin with the shape of circuit used for the farming in eclosery. Ration: Total quantity of food provided to an animal during one 24 hours period. Recruitment: Process of integration of one new generation to the global population. By extension, the new class of juveniles itself. Repopulation: Action to released in large number in the natural environment of the organisms produced in eclosery, with an aim of reconstitution of impoverished stocks. Resilience: Refer to the aptitude of an ecological system or a system of subsistence to be restored after tensions and shocks.

Point, reference: Point usually fixes identified on the ground by a reference mark placed at the end of a line of sight. (see Benchmark).

Respiration: Process by which a living organism, plants or animal, combines oxygen and organic matter, releasing from energy, carbonic gas (CO2) and other products. [Syn.: breathing].

Polyculture: The farming of at least two noncompetitive species in the same unit of farming.

Rhizome: Thick and horizontal stem, generally underground, which emits growths to the top and of the roots downwards.

Porosity: Free space between the particles or the lumps ones in the soil.

S

Post-larva: Stage which follows that of the larva immediately and presents some characters of the juveniles one.

Scrubbing: In-depth migration of the soluble substances or colloids in the interstices of the ground.

Pressure loss: The pressure loss is due for example to the friction or the shifting

Sedentary: Who moves little and remains in his habitat.

Subsistence fishfarming in Africa

Selection (genetic): Action to choose the individuals presenting interesting properties and use it as breeder. Size, commercial: Minimal size that the organism must reach to have the right to be sold.

Trace element: Metal or metalloid, present in small quantity (= with the state of trace) in living tissue and necessary to the metabolism of these tissues.

Size, portion: Size of a consumable fish by only one person.

Traceability: Ability to trace the whole course of a product or an organism since its farming until its sale.

Slaked lime: Lime paste obtained by addition of water to quicklime.

Trophic: Who rerers to the nutrition of the organs and tissues.

Spawning: General term to indicate of ovules, fertilized or in front of being fertilized; also used for eggs fertilized, as well as very young fish of the same class of recruitment, generally many.

Turbidity: Disturbance or reduction of the penetration of the light in water resulting from the presence of suspended matter, colloidal or dissolved, or of the presence of planktonic organisms.

Swim bladder: Organ filled with a gas mixture rich in oxygen and allowing the stabilization of osseous fish in water. This organ is connected to the esophagus. The cartilaginous fish (group of the selacians like the rays and the sharks) do not have any.

U

T Taxonomy: Classification of the fossil and alive organisms according to their evolutionary relations. Tenure: Socially defined agreements, often described in terms “of whole of rights” held by individuals or groups (recognized either legally, or customary), concerning the rights of access and the rules of use of grounds or resources which are associated there, such as individual trees, plant species, water or animals. Thermocline: Zone of a water level thermically stratified (e.g sea, lake, reserve of water) located under the surfacing, where the variation in temperature increases abruptly (i.e where the temperature decreases quickly with the increase depth). A thermocline constitutes usually an ecological barrier and its oscillations influence considerably the distribution and the productivity of stocks.

V Vitamin: Substance necessary in very small amount for the good development of the body and its vital functions. Vitelline: Nutritive cells, substances or stuctures being used as endogenous food of eggs or larvae. Vitellus: Total of the nutritive reserves built-in the cytoplasm of an egg.

W X Y Z Zoobenthos: Benthic fauna. Zooplankton: Microscopic animals living in suspension in the water mass. Animal component of the plankton. Zoosanitary: Who deals with animal health. Zootechnical: Technological knowledge to ensure the success of an animal farming.

Subsistence fishfarming in Africa

185

186

Subsistence fishfarming in Africa

Appendix

Contents • Examples of files • Table of data • Some elements of the biology of the species • Biogeographic data • File of species

Subsistence fishfarming in Africa

187

CONTENTS - APPENDIX Appendix 01 - EXAMPLES OF FILES

189

I. FILES FOR MONITORING THE PONDS

189

II. FILES FOR THE FOLLOW-UP OF THE FISH

191

Appendix 02 - TABLE OF DATA

193

Appendix 03 - SOME ELEMENTS OF THE BIOLOGY OF THE SPECIES

207

I. THE MORPHOLOGY AND THE SYSTEMATIC

207

II. THE BIOLOGY OF CICHLIDAE

216

II.1. The taxonomy

216

II.2. The feeding habits

217

II.3. The reproduction and parental care

218

III. THE BIOLOGY OF SILURIFORMES OR CATFISH

226

III.1. The Clariidae

226

III.2. The Claroteidae and Auchenoglanididae

231

III.3. The Schilbeidae

233

III.4. The Mochokidae

233

IV. THE OTHER FAMILIES

234

IV.1. The Cyprinidae

234

IV.2. The Citharinidae

234

IV.3. The Distichodontidae

236

IV.4. The Channidae

236

IV.5. The Latidae

237

IV.6. The Arapaimidae

237

Appendix 04 - BIOGEOGRAPHIC DATA

239

Appendix 05 - FILE OF SPECIES

255

Cover photo: Ö Ö Cichlidae, Hemichromis fasciatus in the wild, Liberia, ASUR, 2006 - © Yves Fermon, Claire Gsegner

188

Subsistence fishfarming in Africa

Appendix 01 EXAMPLES OF FILES

Are given here some models of: 1. Files to monitor ponds as a whole. These files can be used for all ponds, or separately for each pond. It will then be enough to make a synthesis of the individual record files of the ponds. 2. Files for the follow-up of fish. Again, this can be done by species, pond, for all the ponds… These are examples and should be changed according to the operation implementation. There is, however, the information necessary for proper management of ponds and fish stocks.

I. FILES FOR MONITORING THE PONDS Daily fish per pond Pond n° Date Activities and remarks

Month Money  spent

Dead  fish

Year

Fish given Workers

Fish sold

Family Quantity Income

Total of the month

Subsistence fishfarming in Africa

189

Annual balance per pond Pond n° Month

Years Money  spent

Dead  fish

Fish given To workers To family

Fish sold Total

Quantity

Income

January February March April May June July August September October November December Total  99 Date: Date of the observation; 99 Activities and remarks: The activities made on the ponds (Feeding, cleaning the dikes…) and the remarks (water colour, flow…); 99 Money spent: Money spent for one activity (manpower…) 99 Dead fish: Number, weight, species of dead and removed fish; 99 Given fish: Fish given to the workers of for familial consumption; 99 Sales fish: Fish sold at the market or at the exterior to obtain money. At the end of the year or at the end of the cycle, then it is possible to make a general assessment of activities, income and consumption in general, where appropriate, to improve the operating system for the other cycles.

190

Subsistence fishfarming in Africa

II. FILES FOR THE FOLLOW-UP OF THE FISH Here are two types of files to follow-up the fish: 1. The first two correspond to the quantitative aspects of production. They allow to know by pond and all ponds, the fish production. 2.

The third file is by species and fish or batch of fish to estimate growth and evolution of the relationship weight / size of fish.

All this information will provide elements to improve production for the next cycle (density by species, additional food, cycle time…).

Fish stock

Date

Pond n°

Surface or volume (V)

Species Introduction date

Di

End date

Df

Duration (days)

Df - Di

Initial number

Ni

Initial biomass (g)

Bi

Initial mean weight (g)

Pmi

Initial density

Ni / V

Initial mean size (cm)

Tmi

Dead fish Final number

Nf

Final biomass (g)

Bf

Final mean weight (g)

Pmf

Final mean size (cm)

Tmf

Total ration (g)

RT

Total production (g)

Bf - Bi

Conversion rate

RT / (Bf - Bi)

Day growth (g)

(Pmf - Pmi) / days

Day growth (cm)

(Tmf - Tmi) / days

Survival (%)

(Nf - Ni) x 100

Subsistence fishfarming in Africa

191

Evaluation sheet for growth and production

Date Pond

Surface or volume Controle n° Beginning date

Di

End date

Df

Duration (days)

Df - Di

Initial numbers

Ni

Initial biomass (g)

Bi

Initial mean weight (g)

Pmi

Dead fish Final number

Nf

Final biomass (g)

Bf

Final mean weight (g)

Pmf

Total ration (g)

RT

Total production (g)

Bf - Bi

Conversion rate

RT / (Bf - Bi)

Day growth (g)

(Pmf - Pmi) / jours

Survival (%)

(Nf - Ni) x 100

Monitoring of fish - Size / Weight - individual or mean Pond n° Species

192

Date Nomber

Sex

Subsistence fishfarming in Africa

 Standard  length (cm)

Weight (g)

Remarks

Appendix 02 TABLES OF DATA

Are presented here ici a series of tables given informations on: Table XXXVIII. The tonnage of halieutic products by African countries. Table XXXIX. The checklist of freshwater species which have been the subject of an introduction in Africa. Table XL.

The list of freshwater species introduced by African countries.

Table XLI.

The list of freshwater species used for aquaculture in Africa.

Subsistence fishfarming in Africa

193

Table XXXVIII. The tonnage of halieutic products in 2005 per African countries (FAO, 2006). Country South Africa Algeria Angola Benin Botswana Burkina Faso Burundi Cameroon Central African Republic Congo Congo DR / Zaïre Côte d’Ivoire Djibouti Egypt Erythrea Ethiopia Gabon Gambia Ghana Guinea Equatorial Guinea Guinea-Bissau Kenya Lesotho Liberia Libya Madagascar Malawi Mali Morocco Mauritania Mozambique Namibia Niger Nigeria Uganda Rwanda Senegal Sierra Leone Somalia Sudan Swaziland Tanzania Chad Togo Tunisia Zambia Zimbabwe Total

194

Fish, crustaceans, molluscs

Aquatic plants

Capture

Aquaculture

Total

Capture

Aquaculture

Total

817608 126259 240000 F 38035 132 9000 14000 F 142345 15000 F 58368 220000 F 55000 F 260 F 349553 4027 9450 43863 32000 F 392274 96571 F 3500 F 6200 F 148124 45 10000 F 46073 F 136400 58783 100000 F 932704 247577 42473 552695 50018 523182 416758 7800 F 405070 145993 30000 F 62000 70 F 347800 F 70000 F 27732 109117 65000 F 13000 F

3142 368 F 372 6F 200 F 337 0 80 2965 F 866 F 539748 0 78 0 1154 0 1047 1 0 266 F 8500 F 812 1008 F 2257 1222 50 F 40 56355 10817 386 F 193 F 0 1600 F 0 11 F 1535 2665 5125 F 2452

820750 126627 F 240000 F 38407 132 9006 F 14200 F 142682 15000 F 58448 222965 F 55866 F 260 F 889301 4027 9450 43941 32000 F 393428 96571 F 4027 6200 F 149171 46 10000 F 46339 F 144900 F 59595 101008 F 934961 247577 43695 552745 F 50058 579537 427575 8186 F 405263 F 145993 30000 F 63600 F 70 F 347811 F 70000 F 29267 111782 70125 F 15452 F

6619 12813 0 0 0 240 F -

3000 90 F 56 67 F 1 6000 F -

9619 90 F 12813 56 67 F 1 0 6240 F -

93253346

48149792

141403138

1305803

14789972

16095775

Subsistence fishfarming in Africa

Table XXXIX. The checklist of freshwater species which have been the subject of an introduction in Africa (FAO, 2006; Fishbase, 2006). Environment (E): Found in: m = marines, s = brackish Maximal size (T): SL = Standard Length - FL = Fork Length - TL = Total Length; m = male; f = female; ns = non sex Aquaculture (A): 1 = used for consumption Order

Family

Osteoglossiformes (Bony tongues)

Arapaimidae

Anguilliformes (Eels) Clupeiformes (Herrings, sardines) Cypriniformes (Carps, minnows)

Characiformes (Tétra) Siluriformes (Catfish)

Salmoniformes (Salmons)

Anguillidae

Species Heterotis niloticus Anguilla anguilla

Clupeidae

Limnothrissa miodon

Cyprinidae

Aristichthys nobilis Barbus anoplus Barbus barbus Carassius auratus auratus Carassius carassius Catla catla Ctenopharyngodon idella Cyprinus carpio carpio Gobio gobio gobio Hypophthalmichthys molitrix Labeo rohita Labeobarbus aeneus Labeobarbus natalensis Mylopharyngodon piceus Rutilus rubilio Rutilus rutilus Scardinius erythrophthalmus Tanichthys albonubes Tinca tinca Distichodus niloticus Astyanax orthodus Bagrus meridionalis Schilbe mystus Clarias gariepinus Ictalurus punctatus Silurus glanis Hucho hucho Oncorhynchus mykiss Salvelinus fontinalis Salmo trutta fario Salmo trutta trutta

Citharinidae Characidae Bagridae Schilbeidae Clariidae Ictaluridae Siluridae Salmonidae

Esociformes (Pikes)

Esocidae

Cyprinodontiformes (Killis, mosquito fish)

Aplocheilidae Cyprinodontidae Poeciliidae

Esox lucius Pachypanchax playfairii Aphanius fasciatus Gambusia affinis Gambusia holbrooki Phalloceros caudimaculatus Poecilia latipinna Poecilia reticulata Xiphophorus hellerii Xiphophorus maculatus

Author

E

(Cuvier, 1829) (Linnaeus, 1758)

m-s

(Boulenger, 1906) (Richardson, 1845) Weber, 1897 (Linnaeus, 1758) (Linnaeus, 1758) (Linnaeus, 1758) (Hamilton, 1822) (Valenciennes, 1844) Linnaeus, 1758 (Linnaeus, 1758) (Valenciennes, 1844) (Hamilton, 1822) (Burchell, 1822) (Castelnau, 1861) (Richardson, 1846) (Bonaparte, 1837) (Linnaeus, 1758) (Linnaeus, 1758) Lin, 1932 (Linnaeus, 1758) (Hasselquist, 1762) Eigenmann, 1907 Günther, 1894 (Linnaeus, 1758) (Burchell, 1822) (Rafinesque, 1818) Linnaeus, 1758 (Linnaeus, 1758) (Walbaum, 1792) (Mitchill, 1814) Linnaeus, 1758 Linnaeus, 1758

s

s

s s s

s

m-s

T

A

100 SL m

1

200 TL ns

1

17.5 TL ns 146 SL ns 10.1 FL f 90 SL ns 41 TL ns 64 TL ns 120 TL ns 150 TL ns 120 SL ns 13 SL ns 100 TL ns 96 TL ns 50 FL m 68.3 TL m 180 SL ns 25.8 FL f 45 SL ns 35 SL ns 2.2 SL ns 64 TL ns 83 TL m 10 TL m 97 TL f 34 SL ns 150 SL ns 100 SL ns 500 TL ns 165 SL ns 100 SL ns 85 SL ns 60 TL ns 140 TL ns

Linnaeus, 1758

s

150 TL ns

(Günther, 1866) (Valenciennes, 1821) (Baird & Girard, 1853) Girard, 1859 (Hensel, 1868) (Lesueur, 1821) Peters, 1859

s m-s s s

Heckel, 1848

s

10 SL m 6 SL ns 4.2 SL ns 6 SL f 5.2 TL ns 12 SL ns 5 SL f 14 TL m 16 TL f 4 SL m

(Günther, 1866)

s

1 1 1 1 1

1

1 1 1

1 1

Subsistence fishfarming in Africa

195

TABLE XXXIX (next). The checklist of freshwater species which have been the subject of an introduction in Africa (FAO, 2006; Fishbase, 2006). Environment (E): Found in: m = marines, s = brackish Maximal size (T): SL = Standard Length - FL = Fork Length - TL = Total Length; m = male; f = female; ns = non sex Aquaculture (A): 1 = used for consumption Order

Family

Species

Author

Perciformes (Perch, gobies)

Moronidae Terapontidae Latidae

Morone saxatilis Terapon puta Lates niloticus Lepomis cyanellus Lepomis gibbosus Lepomis macrochirus Lepomis microlophus Micropterus dolomieu Micropterus punctulatus Micropterus salmoides Perca fluviatilis Sander lucioperca Amatitiana nigrofasciata Astatoreochromis alluaudi Astronotus ocellatus Oreochromis andersonii Oreochromis aureus Oreochromis esculentus Oreochromis karongae Oreochromis leucostictus Oreochromis macrochir Oreochromis mortimeri Oreochromis mossambicus Oreochromis niloticus eduardianus Oreochromis niloticus niloticus Oreochromis shiranus shiranus

(Walbaum, 1792) Cuvier, 1829 (Linnaeus, 1758) Rafinesque, 1819 (Linnaeus, 1758) Rafinesque, 1819 (Günther, 1859) Lacepède, 1802 (Rafinesque, 1819) (Lacepède, 1802) Linnaeus, 1758 (Linnaeus, 1758) (Günther, 1867) Pellegrin, 1904 (Agassiz, 1831) (Castelnau, 1861) (Steindachner, 1864) (Graham, 1928) (Trewavas, 1941) (Trewavas, 1933) (Boulenger, 1912) (Trewavas, 1966) (Peters, 1852) (Boulenger, 1912) (Linnaeus, 1758) Boulenger, 1897

Centrarchidae

Percidae Cichlidae

Eleotridae Anabantidae Osphronemidae

Channidae Lepidosireniformes (Lung fish)

196

Protopteridae

Subsistence fishfarming in Africa

E m-s s

s s

s s

s s s

Günther, 1894

Oreochromis spilurus spilurus

(Günther, 1894)

s

(Trewavas, 1966) (Boulenger, 1896) (Günther, 1864) Trewavas, 1936 (Boulenger, 1897) Smith, 1840 (Gervais, 1848) (Bleeker, 1849) (Boulenger, 1912) (Linnaeus, 1758) Lacepède, 1801 (Pallas, 1770) (Bloch, 1793) (Lacepède, 1801)

s

Heckel, 1851

A 1 1

1 1

1 1 1 1 1 1 1

32 SL m 29 SL f

Oreochromis spilurus niger

Oreochromis urolepis hornorum Serranochromis robustus jallae Serranochromis robustus robustus Tilapia guinasana Tilapia rendalli Tilapia sparrmanii Tilapia zillii Butis koilomatodon Microctenopoma ansorgii Macropodus opercularis Osphronemus goramy Trichogaster trichopterus Channa striata Channa maculata Protopterus aethiopicus aethiopicus

T 200 TL m 30 TL ns 200 TL m 31 TL m 32 SL ns 41 TL m 43.2 TL m 69 TL m 63.5 TL m 65 SL ns 60 SL ns 130 TL ns 10 SL 19 SL ns 45.7 TL m 61 TL m 45.7 TL m 50 SL m 38 SL ns 32 TL ns 40.2 TL m 48 TL ns 39 TLns 49 TL ns 64 TL ns 39 SL ns

s s m-s

19.2 SL m 16.3 SL f 24 SL m 39.6 SL m 56 TL m 14 TL m 45 TL ns 23.5 TL m 27 SL ns 10.7 TL m 8 TL m 5.3 SL ns 70 SL m 15 SL m 91.5 ns 25 SL ns 200 TL ns

1 1 1

Table XL. List of species introduced by African countries.

Clupeidae

Limnothrissa miodon

Cyprinidae

Aristichthys nobilis Barbus anoplus

N

N

o

Ethiopia

I

Djibouti

I

Côte d’Ivoire

Comoros

Central Africa

Cape Verde

I

Erythrea

N

Egypt

N

Cameroon

Burundi

Burkina Faso

Botswana

Benin N

Congo DR

Heterotis niloticus Anguilla anguilla

Congo

Arapaimidae Anguillidae

Angola

Species

Algeria

Country Family

South Africa

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic o = introduce but not established - q = to be verified

N

NI

I

o

N

Barbus barbus Carassius auratus auratus

I

I

Carassius carassius

I

Catla catla Ctenopharyngodon idella

I

I

Cyprinus carpio carpio

I

o

I

I

I

I

I

I

I

I

I

I

I

o

I

N

N

Gobio gobio gobio Hypophthalmichthys molitrix Labeo rohita Labeobarbus aeneus

N

Labeobarbus natalensis

N

Mylopharyngodon piceus Rutilus rubilio Rutilus rutilus Scardinius erythrophthalmus Tanichthys albonubes Tinca tinca Citharinidae

Distichodus niloticus

Characidae

Astyanax orthodus

Bagridae

Bagrus meridionalis

Schilbeidae

Clarias gariepinus

Ictaluridae

Ictalurus punctatus

Siluridae

Silurus glanis

Salmonidae

Hucho hucho

Esocidae Cyprinodontidae Poeciliidae

N

Schilbe mystus

Clariidae

Aplocheilidae

I

N

N

N

N

N

N

N

I

N N

N

I

N

N

I

N N

N

N N

N

I

I

I

Oncorhynchus mykiss

I

Salmo trutta fario

I

Salmo trutta trutta

I

Salvelinus fontinalis

o

Esox lucius

I I

I

Pachypanchax playfairii Aphanius fasciatus Gambusia affinis

N I

N I

I

Gambusia holbrooki

I

I I

Phalloceros caudimaculatus Poecilia latipinna Poecilia reticulata

I

Xiphophorus hellerii

I

I

Xiphophorus maculatus

Subsistence fishfarming in Africa

197

TABLE XL (next ). List of species introduced by African countries.

Morone saxatilis Terapon puta

Moronidae Terapontidae

Lepomis cyanellus

Centrarchidae

Ethiopia

Erythrea

Egypt

Djibouti

Côte d’Ivoire

Congo DR

I N

N

I

I

N

N

N

I

Lepomis gibbosus Lepomis macrochirus

Congo

Comoros

Central Africa

Cape Verde

Cameroon

Burundi

Burkina Faso

Botswana

I

Lates niloticus

Latidae

Benin

Angola

Species

Algeria

Country Family

South Africa

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic o = introduce but not established - q = to be verified

I I

I

Lepomis microlophus

Percidae

Micropterus dolomieu

I

Micropterus punctulatus

I

Micropterus salmoides

I

Perca fluviatilis

I

Sander lucioperca

I

I

o

o

o

I

Amatitiana nigrofasciata

Cichlidae

Astatoreochromis alluaudi

I

I

I

I

Astronotus ocellatus

I

Oreochromis andersonii

I

Oreochromis aureus

I

N

N

I N

N

Oreochromis esculentus Oreochromis karongae Oreochromis leucostictus Oreochromis macrochir

I o

I

N

o

N

I

I

N I

I

o

Oreochromis mortimeri

I

I

o

I

I

Oreochromis mossambicus

I

I

I

N

I

Oreochromis niloticus eduardianus Oreochromis niloticus niloticus

N

N I

I

I N

I

I

I

I

I

I

Oreochromis shiranus shiranus Oreochromis spilurus niger

N

Oreochromis spilurus spilurus

I

Oreochromis urolepis hornorum Serranochromis robustus jallae

N I

I

N

N

Tilapia rendalli

N

N

N

Tilapia sparrmanii

N

N

N

N

Serranochromis robustus robustus Tilapia guinasana

I

Tilapia zillii

I

N

N

N

N

N

N N

I N

N

I

I

N 9

N 4 11

Butis koilomatodon

Eleotridae Anabantidae

Microctenopoma ansorgii

Osphronemidae

Macropodus opercularis Osphronemus goramy

N

N

o

o

Trichogaster trichopterus Channidae

Channa maculata Channa striata

Protopteridae

198

Protopterus aethiopicus aethiopicus Number of introductions 24 11 1

Subsistence fishfarming in Africa

2

4

1

N 4

4

0

6

N 3 12 8

9

0

TABLE XL (next ). List of species introduced by African countries.

Arapaimidae Anguillidae

Heterotis niloticus Anguilla anguilla

Clupeidae

Limnothrissa miodon

Cyprinidae

Aristichthys nobilis

I

N

N I

Namibia

Mozambique

Mauritania

Mauritius

Morocco

Mali

Malawi

Madagascar

Libya

Liberia

Lesotho

Kenya

Guinée-Bissau

Guinea

Ghana

Gabon

Species

Gambia

Country Family

Guinea Equatorial

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic o = introduce but not established - q = to be verified

I N

N I I

Barbus anoplus

o

N

I

Barbus barbus

I

Carassius auratus auratus

I

Carassius carassius

I

I

I

Catla catla

I

Ctenopharyngodon idella

I

Cyprinus carpio carpio

I

I

I

I

o

Gobio gobio gobio

I

I

o

I

I

I

I

o

I

I

Hypophthalmichthys molitrix

o

Labeo rohita

I

Labeobarbus aeneus

o

I

I

N

N

Labeobarbus natalensis Mylopharyngodon piceus

I

Rutilus rubilio Rutilus rutilus

o

I

Scardinius erythrophthalmus

o

I

Tanichthys albonubes

I

Tinca tinca Citharinidae

Distichodus niloticus

Characidae

Astyanax orthodus

Bagridae

Bagrus meridionalis

Schilbeidae

Clarias gariepinus

Ictaluridae

Ictalurus punctatus

Salmonidae

Esocidae Aplocheilidae Cyprinodontidae Poeciliidae

I I N

Schilbe mystus

Clariidae Siluridae

o N

N I

N

N

N N

N

N

N

N

N

N N

N

N N

Silurus glanis Hucho hucho

I

Oncorhynchus mykiss

I

Salmo trutta fario

I

Salmo trutta trutta

I

Salvelinus fontinalis

I

I

I

I

I o q

Gambusia holbrooki

I

o I

N I

o

o

Pachypanchax playfairii Gambusia affinis

I

I

Esox lucius Aphanius fasciatus

I

I

I

I

I

I

Phalloceros caudimaculatus

I

I I

I

Poecilia latipinna

I

Poecilia reticulata

I

I

I

I

Xiphophorus hellerii

I

I

I

Xiphophorus maculatus

I

I

Subsistence fishfarming in Africa

199

TABLE XL. (next ). List of species introduced by African countries.

Morone saxatilis Terapon puta

Moronidae Terapontidae

N

N NI

Lepomis cyanellus

Centrarchidae

Namibia

N

Lates niloticus

Latidae

Mozambique

o

Mauritania

Morocco

N

Mauritius

Mali

Malawi

Madagascar

Libya

Liberia

Lesotho

Kenya

Guinée-Bissau

Guinea

Ghana

Gabon

Species

Gambia

Country Family

Guinea Equatorial

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic o = introduce but not established - q = to be verified

N

q

o

I

Lepomis gibbosus

N I

I

Lepomis macrochirus

q

I

I

Lepomis microlophus

I

I

I

I

Micropterus dolomieu

I

Micropterus punctulatus Micropterus salmoides

I

I

I

I

I

Percidae

Perca fluviatilis

I

Sander lucioperca

I

Cichlidae

Amatitiana nigrofasciata Astatoreochromis alluaudi

I

o

I

I

N

Astronotus ocellatus Oreochromis andersonii

I

Oreochromis aureus

o

Oreochromis esculentus

N

N o

I

Oreochromis karongae

NI

Oreochromis leucostictus Oreochromis macrochir

N

I I

I

I

Oreochromis mortimeri

q

Oreochromis mossambicus

I

Oreochromis niloticus eduardianus

I

Oreochromis niloticus niloticus

N

I

N

I N

I N

Oreochromis spilurus spilurus

N

I

N

I

I

I

Oreochromis shiranus shiranus Oreochromis spilurus niger

I

I

o

N

I

I

Oreochromis urolepis hornorum Serranochromis robustus jallae

N

N

Serranochromis robustus robustus

N

N

Tilapia guinasana Tilapia rendalli

E N

I

I

N

I

Tilapia sparrmanii

I

Tilapia zillii

N

N

N

N

Butis koilomatodon

N

Anabantidae

Microctenopoma ansorgii

I

Osphronemidae

Macropodus opercularis

I

Osphronemus goramy

I

Eleotridae

I

N

N

N N

N

I

N

I

Trichogaster trichopterus Channidae

I

Channa maculata

I

Channa striata Protopteridae

200

Protopterus aethiopicus aethiopicus Number of introductions

Subsistence fishfarming in Africa

N

N

I 4

0

3

0

0

N 0 22 4

1

1 35 8

I 0 25 23 1

7

9

TABLE XL. (next ). List of species introduced by African countries.

Clupeidae

Limnothrissa miodon

Cyprinidae

Aristichthys nobilis

N

N

I

NI

I

N

Barbus barbus Carassius auratus auratus

I

I

Carassius carassius Catla catla Ctenopharyngodon idella

I

Cyprinus carpio carpio

I

I

I

I

I

I

I

o

I I

I

I

Number of native 0

7

0 0

I

28 0

15 0 o

0

10 0 I

4

0

Labeobarbus aeneus

o

I

1

3

Labeobarbus natalensis

I

1

1

Rutilus rubilio

1

0

I

1

0

2

0

I

3

0

Rutilus rutilus Scardinius erythrophthalmus Tanichthys albonubes Tinca tinca Citharinidae

Distichodus niloticus

Characidae

Astyanax orthodus

Bagridae

Bagrus meridionalis

o N

Clariidae

Clarias gariepinus Ictalurus punctatus

Siluridae

Silurus glanis

Salmonidae

Hucho hucho

o

N

N

N

N

N

N

N N

1

0

6

0

1

6

1

0

I

1

3

N

1 23

I

N N

Schilbe mystus

Ictaluridae

N

N

N

N

N

N

N

N

2 26

I

1 I

Oncorhynchus mykiss

I

I

I

I

I

I

o

o

0

1

0

16 0

I

10 0

3

Salmo trutta trutta Salvelinus fontinalis

I

Esox lucius

I

I

Pachypanchax playfairii

E

I

Aphanius fasciatus

N

Gambusia affinis

I

Gambusia holbrooki

o

I

0

4

0

6

0

1

0

1

4

13 0 5

0

Phalloceros caudimaculatus

1

0

Poecilia latipinna

1

0

Poecilia reticulata

I

0

2 I

Salmo trutta fario

Poeciliidae

3

1

0

Mylopharyngodon piceus

Aplocheilidae

0

1

2

I

Labeo rohita

Cyprinodontidae

4

1

Hypophthalmichthys molitrix

Esocidae

3 2

I

Gobio gobio gobio

Schilbeidae

2 5

2 I

I

Number of introduced

6 10

N

Barbus anoplus

Zimbabwe

I

Zambia

N

Tunisia

Tanzania

Swaziland

Sudan

Somalia

Sierra Leone

Seychelles

Senegal

Rwanda

Uganda

N

Togo

Heterotis niloticus Anguilla anguilla

Chad

Arapaimidae Anguillidae

Nigeria

Niger

Species

Reunion La

Country Family

Sao Tome & Principe

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic o = introduce but not established - q = to be verified

I

Xiphophorus hellerii Xiphophorus maculatus

I

I I

I

I

I

I

11 0

o

6

0

4

0

Subsistence fishfarming in Africa

201

TABLE XL (next ). List of species introduced by African countries.

Lates niloticus

Latidae

N

NI

N

N

I

N

I

I

o

Lepomis gibbosus Lepomis macrochirus

I

o

I

Lepomis microlophus Micropterus dolomieu

o

Micropterus punctulatus

I

Micropterus salmoides

o

I

I I

I

Sander lucioperca N

N

Oreochromis esculentus

N

N

N

I

Oreochromis karongae Oreochromis leucostictus

N

I

Oreochromis macrochir

I

Oreochromis niloticus eduardianus

N

Oreochromis niloticus niloticus

I I

4

1

0

o

5

3

o

7

7 2 2

I

I

I

I

4

2

N 20

5

I N N

I

I

I

I

Oreochromis urolepis hornorum

N

N N

Serranochromis robustus jallae

I

Serranochromis robustus robustus

I

N N N

N

Tilapia guinasana Tilapia rendalli

N

I

I

N

N

Tilapia sparrmanii Tilapia zillii

N N N

Butis koilomatodon

Eleotridae

N

I

N N

N I N

N N N

1

2

15

2

2

5

18

2

1

2

3

2

2

4

1

2

2

7

1

4

1

0

N

7

12

N N

1

10

5

22

1

4 2

Anabantidae

Microctenopoma ansorgii

1

Osphronemidae

Macropodus opercularis

1

0

I

6

0

I

3

0

1

0

2

0

Osphronemus goramy

o

Trichogaster trichopterus Channidae

I

Channa maculata Channa striata

Protopteridae

202

N

0

1

N

N

1

N

Oreochromis spilurus niger I

0

4

N

Oreochromis spilurus spilurus

0

3

2

I

Oreochromis shiranus shiranus

2

NI

I

I

0

0

N N I

0

2

21

I

Oreochromis mortimeri Oreochromis mossambicus

9

I

I

I

I

0 0

0

I N N o

8 2

0

N

Oreochromis andersonii

14

3

Astronotus ocellatus Oreochromis aureus

3

5

6

I

Astatoreochromis alluaudi

0

1

I

I

Amatitiana nigrofasciata

Cichlidae

1

o o

Perca fluviatilis

Percidae

Number of native

Zimbabwe

Zambia

Tunisia

Chad Togo

Tanzania N

Lepomis cyanellus

Centrarchidae

Swaziland

Sudan

N

Number of introduced

Morone saxatilis Terapon puta

Moronidae Terapontidae

Somalia

Sierra Leone

Seychelles

Senegal

Rwanda

Uganda

Nigeria

Niger

Species

Reunion La

Country Family

Sao Tome & Principe

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic o = introduce but not established - q = to be verified

Protopterus aethiopicus aethiopicus Number of introductions

Subsistence fishfarming in Africa

0

N I 8 9 10 11 0

0

5

0

N N N 1 9 0 5 10 16 0 3 12 14 21 381 217

Table XLI. List of freshwater fish used in aquaculture by country (FAO, 2006; Fishbase, 2008).

IA

IA IA A

A N

N IA I

N

I

IA

N N N N N N N N N A N N N N N N N N N N N N N I N N N

I N N N A

I I I

N N N N A

A

N N

N

N A N N A N A I N N N N N

N NX

I IA N

N

N o

I

I o

N

N o N I I I I I N I A IA A

N

0 0 1 12

I I I N

N

N

A

N

o N I I I o IA I IA IA A

I I A

N N N N X

N

I

I I

IA N

N N

N 5 3 8 4

N N

I

N N

N

N N N N N N IA N N N

N A A IA N o

N

N I I

N

N

N N

N N

7 5 11 6

IA IA oA

I

I I o A IA

I I

I

N

N IA

A

I IA

I IA IA oA I I

N

N IA N o

IA

N

Ethiopia

Erythrea

Egypt

Djibouti

Côte d’Ivoire

Congo DR

Congo

Comoros

Central Africa

Cape Verde

N

Gambia

N

Cameroon

Burundi

Burkina Faso

Botswana

Benin N

A

Gabon

Heterotis niloticus Anguilla anguilla Carassius auratus auratus Cyprinidae Carassius carassius Cirrhinus cirrhosus Ctenopharyngodon idella Cyprinus carpio carpio Hypophthalmichthys molitrix Scardinius erythrophthalmus Alestidae Brycinus lateralis Bagridae Bagrus bajad Claroteidae Chrysichthys nigrodigitatus Schilbeidae Schilbe intermedius Clarias anguillaris Clariidae Clarias gariepinus Clarias ngamensis Heterobranchus bidorsalis Heterobranchus longifilis Siluridae Silurus glanis Mochokidae Synodontis nigromaculata Oncorhynchus mykiss Salmonidae Salmo trutta trutta Esocidae Esox lucius Liza ramado Mugilidae Mugil cephalus Moronidae Dicentrarchus labrax Terapontidae Terapon puta Latidae Lates niloticus Centrarchidae Micropterus salmoides Percidae Sander lucioperca Oreochromis andersonii Cichlidae Oreochromis aureus Oreochromis karongae Oreochromis macrochir Oreochromis mossambicus Oreochromis niloticus niloticus Oreochromis shiranus shiranus Sargochromis carlottae Sargochromis giardi Sarotherodo galileus galileus Sarotherodon melanotheron melanotheron Serranochromis robustus robustus Tilapia cameronensis Tilapia rendalli Tilapia zillii Number of species used in aquaculture Number of species introduced for aquaculture Number of species introduced Number of species natives Arapaimidae Anguillidae

Angola

Species

Algeria

Country Family

South Africa

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic - o = introduce but not established - q = to be verified A = Commercial production - X = Experimental

N N

N N 0 0 2 11

0 0 3 11

I 2 0 1 5

1 1 3 3

EA N N 4 1 3 14

0 0 0 1

N 3 2 4 2

0 0 1 1

N N N 2 3 2 2 6 4 3 8

N 6 0 5 6

0 0 0 1

N 8 4 7 10

N

I 0 0 4 1

I I 1 1 10 9

N N

N N 3 1 3 0 4 0 3 10

Subsistence fishfarming in Africa

203

TABLE XLI (next). List of freshwater fish used in aquaculture by country (FAO, 2006; Fishbase, 2008).

A A Heterotis niloticus Anguilla anguilla Carassius auratus auratus Cyprinidae Carassius carassius Cirrhinus cirrhosus Ctenopharyngodon idella I Cyprinus carpio carpio Hypophthalmichthys molitrix Scardinius erythrophthalmus Alestidae Brycinus lateralis Bagridae N Bagrus bajad Claroteidae A N N Chrysichthys nigrodigitatus Schilbeidae N Schilbe intermedius A Clarias anguillaris Clariidae A A N Clarias gariepinus Clarias ngamensis A N Heterobranchus bidorsalis A N Heterobranchus longifilis Siluridae Silurus glanis Mochokidae Synodontis nigromaculata Oncorhynchus mykiss Salmonidae Salmo trutta trutta Esocidae Esox lucius Liza ramado Mugilidae N N Mugil cephalus Moronidae Dicentrarchus labrax Terapontidae Terapon puta Latidae A N Lates niloticus Centrarchidae Micropterus salmoides Percidae Sander lucioperca Oreochromis andersonii Cichlidae Oreochromis aureus Oreochromis karongae IA Oreochromis macrochir Oreochromis mossambicus A A Oreochromis niloticus niloticus Oreochromis shiranus shiranus Sargochromis carlottae Sargochromis giardi N N Sarotherodo galileus galileus Sarotherodon melanotheron melanotheron A N Serranochromis robustus robustus Tilapia cameronensis Tilapia rendalli N N Tilapia zillii Number of species used in aquaculture 10 3 0 Number of species introduced for aquaculture 1 0 0 Number of species introduced 2 0 0 Number of species natives 5 8 2 Arapaimidae Anguillidae

204

Subsistence fishfarming in Africa

N N I

IA

A

N

Reunion La

Uganda

Nigeria

Niger

Namibie

Mozambique

Mauritania

Mauritius

Morocco

Mali

Malawi

Madagascar

Libya

Liberia

Lesotho

Kenya

Guinea

Ghana

Species

Guinea-Bissau

Country Family

Guinea Equatorial

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic - o = introduce but not established - q = to be verified A = Commercial production - X = Experimental

N A A

I

N I

I

A I I I

oA IA I o

I I IA IA

IA IA IA I

IA oA o o o

I I

IA IA IA

N A N N N N N N A A N N

N A A N N N

A A

N

IA IA IA I

IA IA I I o

q N N

N N N A

N NI I I

N I

I o

o

I

I NIA

I IA I N IA A

N N N

I I I o

A A

A N N

N 0 0 0 9

I N 5 4 13 8

3 2 4 1

N N N A N A N N N N N N A N A N N A N N N N N A

N A IA o o IA N N N N N N A N N N o N N A IA I o IA I o I N A N N N N I N A A IA A I A A A N A A N N N N N N N N

IA A I A I N N I N 6 1 4 7 3 8 1 1 1 0 4 3 0 6 0 0 1 1 16 5 0 10 10 1 4 4 1 4 6 4 1 9

N A N N 5 11 1 3 1 0 4 4 0 13 2 11

A N 6 0 3 9

IA IA

NI

o

I IA A IA

N

I A 4 2 5 4

5 5 5 0

TABLE XLI (next). List of freshwater fish used in aquaculture by country (FAO, 2006; Fishbase, 2008).

N

Zimbabwe

A I

I

I IA I

I o IA

I I

I I IA oA I IA N N

N N

A

N N N N N N N N N N N N N N A A N N N N N N N N N N N

N N N

A

N

N N

N N A A N N N N IA

I

I I

N N N N N N N N N A

N IA I

o I A A A

N

I

N I N A I

I IA

IA N

N IA I A I A IA N A N I

I IA

A

A

I

I

A oA I o

N

I

N N o IA I

I I

A N A IA I N N N N

N A

N

N N N

N IA N

I 0 0 0 1

3 2 6 1

N N 2 0 0 14

0 0 2 1

N 1 0 0 9

0 0 0 3

N 3 0 4 8

A A I 5 6 2 4 5 11 0 9

N N N 0 0 0 13

A N N 2 0 3 9

N 8 4 10 1

6 2 5 8

4 2 8 9

Number of times used in aquaculture Number of introduiced for aquaculture Number of times introduice Number of times native

I

Zambia

N

Tunisia

Tanzania

Swaziland

Sudan

Somalia

Sierra Leone

Seychelles

N

Togo

Arapaimidae Anguillidae

Chad

Heterotis niloticus Anguilla anguilla Carassius auratus auratus Cyprinidae Carassius carassius Cirrhinus cirrhosus Ctenopharyngodon idella Cyprinus carpio carpio Hypophthalmichthys molitrix Scardinius erythrophthalmus Alestidae Brycinus lateralis Bagridae Bagrus bajad Claroteidae Chrysichthys nigrodigitatus Schilbeidae Schilbe intermedius Clarias anguillaris Clariidae Clarias gariepinus Clarias ngamensis Heterobranchus bidorsalis Heterobranchus longifilis Siluridae Silurus glanis Mochokidae Synodontis nigromaculata Oncorhynchus mykiss Salmonidae Salmo trutta trutta Esocidae Esox lucius Liza ramado Mugilidae Mugil cephalus Moronidae Dicentrarchus labrax Terapontidae Terapon puta Latidae Lates niloticus Centrarchidae Micropterus salmoides Percidae Sander lucioperca Oreochromis andersonii Cichlidae Oreochromis aureus Oreochromis karongae Oreochromis macrochir Oreochromis mossambicus Oreochromis niloticus niloticus Oreochromis shiranus shiranus Sargochromis carlottae Sargochromis giardi Sarotherodo galileus galileus Sarotherodon melanotheron melanotheron Serranochromis robustus robustus Tilapia cameronensis Tilapia rendalli Tilapia zillii Number of species used in aquaculture Number of species introduced for aquaculture Number of species introduced Number of species natives

Rwanda

Species

Senegal

Country Family

Sao Tome & Principe

N = native (if the number is null, the species is coming from another continent) I = introduce - E = endemic - o = introduce but not established - q = to be verified A = Commercial production - X = Experimental

11 3 1 1 1 5 16 2 1 1 1 4 1 3 18 1 2 3 1 1 9 1 2 1 2 5 1 4 3 2 4 1 1 5 7 27 1 1 1 1 3 1 1 7 2 170

5 0 1 1 0 5 16 2 1 0 0 0 0 0 1 0 0 0 1 0 9 1 2 0 0 0 1 0 3 2 2 0 1 3 2 11 0 0 0 0 0 1 0 1 0

6 2 7 2 0 15 27 10 3 0 0 0 0 0 2 0 0 0 2 0 16 10 6 0 0 0 1 3 21 3 5 7 0 20 15 18 1 0 0 0 0 1 0 7 5

10 3 0 0 0 0 0 0 0 7 12 11 18 16 26 8 13 24 0 9 0 0 0 4 26 2 3 16 0 0 3 7 3 5 2 2 2 4 4 22 11 4 1 12 22

72 215 317

Subsistence fishfarming in Africa

205

206

Subsistence fishfarming in Africa

Appendix 03

SOME ELEMENTS OF THE BIOLOGY OF THE SPECIES Some general information of the biology of the some species used in aquaculture is presented here. The biogeographic aspects were approached in the chapter III p. 21.

I. THE MORPHOLOGY AND THE SYSTEMATIC The morphology of fish is one of the elements which allow to determine them. It is very variable and is to be connected to the way of living, with the behaviors and habitus. One will find the main anatomical external terms of a fish on Figure 152 below. Will be given here the morphological characters allowing to distinguish the various species. The drawings and part of the text come from the Fauna of the freshwater and brackish fish of West Africa (IRD, 2004). Dorsal fin

Back

Lateral line

Opercle

Caudal peduncle

Head

Chin Thoat

Caudal fin Chest

Pectoral fins

Belly Anal fin Pelvic fins

Figure 152. Principal terms pertinent to the external morphology of a fish. 99 Ratio body length/body depth ( (L/H) (Figure 153 below) Anguilliform, Serpentiform L / H = 12 - 18

Strongly elongate L / H = 7 - 10

Elongate L / H = 4 - 6

Short or medium L / H = 3 - 4

Deep L / H = 2 - 3

Very deep L / H < 2

Figure 153. Different body shapes.

Subsistence fishfarming in Africa

207

99 Body shape in cross-section (Figure 154 ci-dessous)

A

B

C

D

Figure 154. Cross-section of body. A: Laterally compressed; B: More or less rounded; C: Dorso-ventrally depressed; D: Strongly depressed or dorso-ventrally flattened.

99 The head ¾¾ The jaws (Figure 143 below) The premaxilla(e), the maxilla(e) and in certain families, the supramaxilla(e) of the upper jaw are normally distinguished from the mandible(s) of the lower jaw (A). Depending on species or families, the jaws may be equally long and normally developed (Alestidae, certain Cyprinidae) (B) or strongly elongate, forming a beak (rostrum) (Belonidae) (C); In both cases, the mouth is called «terminal». The jaws may also be unequal, the mouth then being either superior (Cyprinodontidae, Centropomidae) (D), subinferior (certain Mormyridae) (E) or inferior (Mochokidae (F). Finally, some species have a protrusible or protractile mouth (Serranidae, Gerreidae) (G). In certain genera, e.g., Labeo , Garra and Chiloglanis , the mouth has strongly developed lips sometimes forming (e.g., in Chiloglanis ) a sucking disk (H) which allows the fish to cling to rocks and live in rather turbulent waters.

pmx

E

mx md

A

C

G Retracted

Protrused

B

D

F

H

Figure 155. Jaws. A: Premaxilla (pmx), maxilla (mx), mandible (md); B: Jaws equal, prolonged into a beak; C: Jaws equal, normally developed; D: Mouth superior; E: Mouth subinferior; F: Mouth protrusible; G: Mouth inferior; H: Mouth inferior, forming a sucking disk.

208

Subsistence fishfarming in Africa

¾¾ Les dents (Figure 156 ci-dessous) These are inserted on the rim of the jaws, i.e., premaxilla, maxilla, and dentary (mandibular bone), on the longitudinal axis of the roof of mouth (vomer and parasphaenoid(s), on both sides of the mouth roof (palatines and ectopterygoids), and on the upper and lower pharyngeal bones. Finally, certain species have lingual teeth. Evidently, not all of these types of teeth are always present. The different kinds of teeth are distinguished here by the number of cusps they bear. Thus, there are: monocuspid teeth that may be straight (certain Marcusenius species) (A), conical or caniniform (certain Alestidae and Cichlidae) (B and C), cutting (Hydrocynus species, Sphyraenidae) (D) or recurved (Synodontis species) (E); bicuspid teeth (Petrocephalus , Distichodus) (F and G); polycuspid teeth with cusps set in a single plane (certain Alestidae and Cichlidae) (H), and molariform polycuspid teeth with cusps forming a crown (certain Alestidae) (I). There are also other, less common kinds of teeth.

B

A

D

C

F

E

G

H

I

Figure 156. Tooth shapes. Monocuspid straight (A: Marcusenius sp.), conical (B: Brycinus sp. and C: Chromidotilapia sp.), cutting (D: Hydrocynus sp.) and recurved (E: Synodontis sp.). Bicuspid (F: Petrocephalus sp. and G: Distichodus sp.). Polycuspid in one plan (H: Micralestes sp.) and molariform (I: Brycinus sp.). ¾¾ The eyes Depending on families, the eyes may be located in different positions. They are usually lateral, but may be placed dorsally, particularly in the Batoidea and the Pleuronectiformes (where they are furthermore both located on the same side of the head). Finally, they may be protruding as in Periophthalmus. In some species, the eyes are partially covered by an adipose eyelid, a nictitating fold or a nictitating membrane. 1 2 ¾¾ The fontanellae (Figure 157 opposite) The cranial fontanellae are sometimes used as a genus- or species-diagnostic criterion for identification; the fronto-parietal fontanellae in some Alestidae (A), and the frontal and occipital fontanellae in some Clariidae (B).

A

B

Figure 157. Fontanellae. A: Alestes sp.; B: Clarias sp.: frontal (1) and occipital (2).

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¾¾ The barbels (Figure 158 below) there may be three types of barbels. A pair of nasal barbels just behind the posterior nostrils (Bagridae, Clariidae) (A); a pair of maxillary barbels provided with a basal membrane (some Mochokidae) (B), or without basal membrane (some Cyprinidae and Mochokidae); and one (some Cyprinidae) or two (Siluriformes) pairs of mandibular barbels. In certain groups, the maxillary (some Synodontis) and mandibular (all Synodontis) may be branched (C). Finally, the mandibular barbels may be sometimes enclosed in the lips as in Chiloglanis (D). 1

4 2

A

3

B

C

D

Figure 158. Barbels. A: The types: Nasal (1), maxillary (2), outer mandibular (3) and inner (4). B: Membranous maxillary barbels (Synodontis sp.); C: Branched maxillary barbels (Synodontis sp.); D: Mandibular barbels enclosed in the lips (Chiloglanis sp.). ¾¾ The gill cover A bony lid that covers the gill slits in the Osteichthyes. Depending on the group, the branchiostegal membrane that covers the opercular bone may or not be fused to the isthmus of the throat. This is used as an identification criterion in certain Siluriformes. In most cases it is widely open, but in some others, the aperture may be rather small, or strongly reduced. In the Chondrichthyes, the gill slits are not covered by an opercle. ¾¾ The gill arch (Figure 159 below) It is formed by three bones bearing externally the gill filaments and internally, the gill rakers. The upper bone is the epibranchial, the lower ones are the ceratobranchial and the hypobranchial (E). In some species (Polypteridae), the juveniles have 3 4 a pair of external gills (F) which are later reab1 sorbed. This is also the case in the embryos of 2 Protopterus, which have three or four pairs of external gills.

A

¾¾ Accessory aerial breathing organs (Figure 160, p. 211) Some forms have the possibility, thanks to the possession of specialized organs, to survive for some time outside the water without suffering major damage. There are several types of such organs: the branched organ of the Clariidae (A), the lungs of the Protopteridae and Polypteridae (B), the labyrinthiform organ of the Anabantidae (C), the pharyngeal diverticulum of the Channidae (D), the swim bladder of Gymnarchus (E) and Heterotis.

210

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B

C Figure 159. Gill slits without opercule (A: Sharks); gill arch formed by: ceratobranchial (1), gill rakers (2), hypobranchial and epibranchial (3), gill filaments (4) (B); external gill of a young Polypterus sp. (C).

3

2

1

2

4

A

3 1 2 3 1 2

B1

1

B2

C

3

2

1

D

E

3 4

Figure 160. Accessory aerial breathing organs. Branched breathing organs (A: Clarias sp.), branches (1), gills (2), branchial valves (3); position of the swim bladder (1) and the lungs (2 and 3; plates of the labyrinth in an Anabantidae (C), principal plates (1-3), stylet (4); pharyngeal diverticula (D: Parachanna sp.), anterior chamber (1), posterior chamber (2), communication with pharynx (3); digestive tract and swim bladder (E: Gymnarchus sp.), swim bladder (1), opening of pneumatic duct (2). 99 
The body The forms and constitutions of fins, the types of scales and other features make possible to diferenciate species. ¾¾ The fins The fins may be paired (pelvics or ventrals and pectorals) that are equivalent to the members of Tetrapods or unpaired (dorsal, caudal and anal): The paired fins are the pelvics (ventrals) and the pectorals (Figure 161 below). In the Gobiidae, the pelvics are either fused into a ventral disk (A), or united by a transverse membrane. In Periophthalmus, they are also united, while the pectorals allow these fishes to move rather quickly on dry land. In the Siluriformes, the first pectoral-fin ray is often ossified, forming a spine that may be denticulate on one or both margins (B). In the Polypteridae, the pectoral fins are real paddles attached to the trunk by a peduncle (C) that allow the fish to effect a wide range of movements.

A

B

C

Figure 161. Pair fins. Coalesced pair of pelvic fins in a Gobiid species (A); first pectoral-fin ray denticulated on one margin (1) or on both margins (2) (B: Clarias sp.); paddle-shaped pectoral fin (C: Polypterus sp.). The unpaired fin are the dorsal, caudal and anal fins. there are three types of dorsal fin (Figure 162, p. 212): one is supported by simple spinous rays, another with soft, usually branched, rays, and the so-called adipose dorsal fin. The latter is usually placed behind the soft-rayed dorsal (A). Many fishes have two dorsal fins, the first spinous (anterior) and the second soft; or a single dorsal fin with anterior spinous rays followed by soft rays (B). In some species (the majority of Siluriformes), the first ray is represented by a strong, more or less denticulate, spine. Depending on species, the dorsal fin may have different shapes, i.e., outer margin straight, concave or rounded, filamentous. (C). Finally, some species lack dorsal fins (certain Schilbeidae).

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1

2

A

3

B

4

1

1

C

Figure 162. Dorsal fin. 
Soft dorsal (2) preceded by a strong spinous ray (1) and followed by an adipose dorsal (3) (A). Two dorsal fins: spiny rays (1), and simple or branched rays (2), separate (B1) and contiguous (B2). Fin margin straight (1), concave (2), rounded (3) and filamentous (4) (C).

Depending on the relative length of its upper and lower lobes, the caudal fin is termed (Figure 163 below) homocercal, when the lobes are symmetrical (A); heterocercal: when the lobes are externally and internally asymmetrical, with either the upper (Carcharhinidae) (B1), or the lower lobe (some Amphiliidae) (B2) better developed. The shape of the caudal fin may vary with species from rounded to forked, notched, emarginate. (C): In the Cyprinodontidae, caudal-fin shapes are manifold.

A

1

B1

2

3

B2

4

5

6

7

C Figure 163. Caudal fin. Homocercal (A: Citharinus sp.). Heterocercal (B1: Carcharhinus sp.) and (B2: Amphiliidae). Caudal shapes (C): rounded (1), truncate or emarginate (2), concave (3), lunate (4), forked (5), pointed and separated from dorsal and anal fins (6), absent or coalesced with dorsal and anal fins (7).

The morphological diversity of the anal fin may be used for the identification of certain species, especially within the Cyprinodontidae. In some Alestidae, its shape differs between males and adult females. In the Perciformes, the first simple rays are modified into real spines. In some Siluriformes (Schilbeidae, Clariidae), this fin is very well developed while in other families (Gymnarchidae), it is absent.

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¾¾ The scales Two principal types of scales can be distinguished on the basis of their structure (Figure 164 below). The first of these groups is represented by the ganoid scales, characteristic of the Polypteridae, which are thick and rhombic and covered by a shiny outer layer of ganoine (A). The second group comprises two different kinds: the cycloid scales which are thin and smooth (Clupeidae, Alestidae) (B); and the ctenoid scales which bear small spines on their posterior margin (Distichodontidae, Lutjanidae) (C). In the Tetraodontidae, the scales are modified into spicules (D), and in the Syngnathidae they are modified into bony plates separated by areas of naked skin (sutures). The Siluriformes lack scales altogether, except certain Amphiliidae which have bony plates covering the body. Finally, in the Chondrichthyes there are the so-called placoid scales which can be considered as small teeth, also called dermal denticles, which give the skin of these fishes a particularly rough surface (E). In some families there is a midventral crest formed by hardened scales appearing as shields (scutes), i.e., in the Clupeidae (F).

A

C

B

D

E

Figure 164. Different types of scales. A: Ganoid; B: Cycloid; C: Ctenoid; D: Dermic sclerification in Tetraodontidae; E: Placoid (denticules). ¾¾ The lateral line (Figure 165 below) In scaled fishes, this line is communicated with the surrounding water by a longitudinal series of pores which frequently open on the pored lateral-line scales. There are four types of lateral lines: complete, with perforations on all lateral-line scales (Mormyridae and some Alestidae) (A); interrupted, with pored scales on two levels (Cichlidae, Anabantidae) (B); incomplete, with only the anterior scales perforated (some Alestidae and Mugilidae) (C), and absent (some Mugilidae and Nandidae).

A

B

C

Figure 165. Lateral line. A: Complete; B: Interrupted on two levels; C: Incomplete. ¾¾ Electric organs Some families have electric organs variable in shape, power and function, located in different parts of the body. The electric organs of the Gymnarchus species, as well as those of the Family Mormyridae, produce rather weak discharges and seem to serve mainly for the recognition of congeners and obstacles (A and B). Those of the Malapterurus species are capable of much stronger discharges and are used for purposes of defence and attack (C).

A

B

C

Figure 166. Location of electric organs. Gymnarchus (A); Mormyridae (B); Malapterurus (C). The arrows indicate the direction and sense of the electric current inside the organs. The plane is that of the electric plates.

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99 Principal measurements and counts These measures are important to determine the species but also to monitor the fish in a pond. The measurements are presented Figure 153 p. 175. The numbers in parentheses correspond to those indicated on the figures. ¾¾ Total length (1): horizontal distance from front tip of snout to hind tip of caudal fin. ¾¾ Standard length (2): horizontal distance from front tip of snout to base (or articulation) of caudal fin. ¾¾ Body depth (3): maximum vertical depth of fish, excluding fins. ¾¾ Head length (4): depending on families, either the horizontal distance from front tip of snout to hind margin of gill cover, or the horizontal distance from front tip of snout to hind tip of occiput or to the bony rim of the notch formed by the scapular girdle behind the head. ¾¾ Snout length (5): horizontal distance from front tip of upper jaw to anterior margin of eye. ¾¾ Eye diameter (6): horizontal diameter of eye. ¾¾ Interorbital width: minimum width between the orbits. ¾¾ Predorsal length (7): horizontal distance from front tip of snout to the articulation of first dorsalfin ray. ¾¾ Preanal length (8): horizontal distance from front tip of snout to the articulation of first anal-fin ray. ¾¾ Prepectoral length (9): horizontal distance from front tip of snout to the articulation of first pectoral-fin ray. ¾¾ Prepelvic (preventral) length (10): horizontal distance from front tip of snout to the articulation of first pelvic (ventral) - fin ray. ¾¾ Length of dorsal-fin base (11): maximal horizontal distance measured between both ends. ¾¾ Length of anal-fin base (12): see dorsal-fin base. ¾¾ Pectoral-fin length (13): length from articulation of first ray to tip of longest ray. ¾¾ Pelvic (ventral)-fin length (14): see pectoral-fin length. ¾¾ Caudal-peduncle length (15): horizontal distance from hind margin of anal fin (or from that of dorsal fin if this extends further backwards than anal) to base of caudal fin. ¾¾ Depth of caudal peduncle (16): minimum vertical depth of caudal peduncle. One proceed also to a number of counts. ¾¾ Fin formula: the number of spines or simple rays in Roman numerals and that of soft bifurcate (branched) rays, in Arabic numerals (example: III-7). ¾¾ Number of scales in lateral line and/or in a longitudinal series. ¾¾ Number of scales on a transverse series. ¾¾ Number of predorsal scales. ¾¾ Number of scales around caudal peduncle. ¾¾ Number of gill rakers on first gill arch. ¾¾ Number of teeth in the outer and inner rows of upper and lower jaws.

ÖÖ All these features are important to determine which family, genus, species are farmed species.

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1 4 2 5

7

6

11 15

3

16

A

13

9

12

14

10 8

74

5

1

2 11

13

6

15 16

3

B

14

9

12

10 8 7 5

11

15

4

16

3 6

C

14

9 10 8

12 2 1

Figure 167. Principal measurements that may be taken on a fish. A: Characiforme; B: Perciforme; C: Siluriforme. For explanation of numbers, please refer to text.

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II. THE BIOLOGY OF CICHLIDAE This perciform freshwater family fish, which occasionally occurs also in brackish waters, is distributed predominantly in tropical areas of America and Africa, but also in Asia minor, tropical Asia, Madagascar and Sri Lanka. The Cichlidae have a single nostril on either side of head (Figure 168 below). Body shape variable, but never very elongate, more or less compressed and covered with cycloid or ctenoid scales. All fins are present. Lower pharyngeal bones fused together, forming a toothed triangle. The reader may find several files on Cichlidae species in Appendix 05 p. 255. The family is very widely distributed in Africa, where some of the species are of great interest to fish culture. Over a hundred genera have been described for that continent. As was seen before (Chapter 03, paragraph II, p. 21), three genera represent the main species for African aquaculture. Other species, predators, are used for the control of reproduction. 2 1

1 *

3

**

A +

3

B *

**

Figure 168. External features of the Cichlidae. A: Tilapia zillii; B: Haplochromis spp. Family characteristics: 1: A single pair of nostril; 2: Dorsal fin in two continuous parts, hard and soft rays; 3: Lateral line interrupted. Intra-family characteristics: +: Tilapiine mark well visible in juveniles; *: Cycloid scales; **: Ctenoid scales.

II.1. THE TAXONOMY We can generally separate the Tilapiines from the other African Cichlidae by the presence of the tilapiine mark on the dorsal fin, well visible in juveniles, and by the cycloids scales (Figure 154 above). Trewavas (1983) has subdivised the tilapia sensu lato in three main genera, Sarotherodon, Oreochromis and Tilapia sensu stricto. One of the criteria of differentiation was the mode of reproduction. Sometimes in conjunction, other criteria were used. 99 The genus Tilapia comprises exclusively species that attach their eggs to the substrate, unlike all others, which are mouth-breeders. Apart from this ethological character, the Tilapia species differ from those in the other two genera by the following features: lower pharyngeal bone as long as broad and with an anterior part shorter than the toothed part; posterior pharyngeal teeth bicuspid or tricuspid (sometimes quadricuspid) and lower limb of first gill arch with at most 17 gill rakers (against 28 in the other genera). 99 Most species of Oreochromis have been described under the genus Tilapia. On the basis of ethological characters, Trewavas (1983) has included in this genus all species in which mouth breeding is practised exclusively by females. Other diagnostic features of the genus Oreochromis are the small size of scales on belly as compared to those on sides; the genital papilla, well developed in both sexes, the shape of the lower pharyngeal bone (longer than broad or as long as broad, its toothed part as long as, or somewhat longer, than anterior part); and the posterior pharyngeal teeth

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which are either bicuspid, have their lower cusps reduced, or lack distinct cusps altogether. 99 As in the genus Oreochromis, the majority of species placed today in the genus Sarotherodon were originally described under the genus Tilapia. Based on ethological features, Trewavas (1983) has transferred to the genus Sarotherodon those species in which both, males and females, practise mouth breeding. Apart from this ethogical character, the genus Sarotherodon is characterized by the following features: scales on belly almost as large as those on sides; genital papilla smaller in males than in females; lower pharyngeal bone longer than broad, its toothed part shorter than anterior part; posterior pharyngeal teeth either bicuspid, with a reduced lower cusp, or without distinct cusps.

II.2. THE FEEDING HABITS Among the many examples of food diets and the trophic adaptations which are associated, the most remarkable are those observed at Cichlidae of the African Great Lakes. All the types of food existing in these lakes were used by these fish and often with morphological adaptations and adequate behaviors. There exists, for example, in the molluscivorous fish, some species are extractors and others crushing. In the same way, the eaters of epilithic algae have different strategies, some grazing the algae of the rocks, the others cutting them short-nap. One will note also certain particular adaptations like the scales eaters and the fish cleaner which feed on parasites of other fish. The tilapia are, in general, microphagous and/or herbivorous (Table XLII, p. 217 below). However, as for the large majority of Cichlidae, they are the opportunistic, i.e. they are able to feed on a large variety of items. For example, Oreochromis niloticus is a phytoplanktonophagous, i.e. which feed mainly phytoplankton and which can also eat blue algae, zooplankton, sediments rich in bacteria and diatoms, as well as artificial food. Tilapia guineensis has an inferior mouth (in low position). Its diet is not specialized with herbivorous tendency, i.e. he eats everything, especially grasses. Sarotherodon melanotheron is a microphagous, planktivorous and benthophagous, i.e. he eats mainly plankton and organizations living at the bottom (benthos). Table XLII. Diet of several species of tilapia in natural waters. Phytoplankton

Zooplankton

O. aureus

X

X

O. esculentus

X

Species

Algae

Macrophytes

O. jipe O. leucostictus

Detritus

Invertebrates

O mossambicus

X X

X X

X

X

X

X

X

O. pangani

X

X

X

X

O. shiranus O. variabilis

X X

S. melanotheron

X

X

X

T. guineensis

X

X

X

X

X

T. kottae

X

T. mariae

X

T. rendalli

X X

X

X

T. sparrmanii T. zillii

Eggs and lavae of fish

X X

O. niloticus

S. galileus

Periphyton

X X

X

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II.3. THE REPRODUCTION AND PARENTAL CARE Cichlidae present elaborate courtship and which are in connection with their parental care. The mode of care to the fry is one of the criteria of differentiation of the genera of tilapia. There are two principal for Cichlidae which are enumerated below.

II.3.1. SUBSTRATE SPAWNING The tilapia practicing this method of reproduction have been placed in the genus Tilapia. A large part are monogamous. The adhesive eggs are deposited on a hard surface. According to the species, it can be a hidden substrate (crevices of rock, snail shells), or an open substrate (cups generally arranged on the muddy sand or movable soil) (Photo W, p. 219), then fertilized. The eggs are fertilized and hatch after a few days during which the two parents ensure a vigilant guard in general. When the larvae can swim freely, they remain in group close to the substrate under the monitoring of the parents. The eggs are yellowish glue on a stone or piece of wood inside the nest in Tilapia zillii, as shown in Figure 169 below. The more there are cavities, the more there are spawning. One of the parents remains constantly above it nest, to supervise the egg laying and the alevins leave the nest when they reached 8 mm length.

A

C

D

E

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B

Figure 169. Courtship and spawning in a substrate spawner Cichlidae, Tilapia zillii. The female is gray. A and B: The female deposits a first set of eggs on the substrate cleaned in advance. The male remains nearby; C: The female leaves the nesting site, the male passes over the eggs and fertilize them.The A to C sequence is repeated several times; D: Female, become darker, take care and aerates the eggs which have been gathered; E: The female Tilapia zillii clean eggs.

II.3.2. MOUTHBROODING The eggs are larger but relatively fewer than at the substrates spawners. Most of the time, the spawn is carried out on a substrate, often prepared by the male. However, for some pelagic species, the spawn can take place in full water. In general, they are polygamous species. The males form a territory which the females come to visit. One distinguishes three main categories of oral incubation: 99 Maternal incubation is the most frequent system. The spawn takes place on a substrate, and the non-adhesive eggs, laid singy or by small groups, are taken quickly in the mouth by the female. The male deposits its sperm at the time when the female collects eggs or then fertilizes them in the mouth. Mouthbrooding continues until the juveniles are entirely independent. In certain cases, the female release them periodically to feed then takes them in the mouth. It is the case of all Haplochromines and the genus Oreochromis. The females can incubate at the same time eggs fertilized by several partners. 99 Paternal incubation is practiced by some species only. It is the case for Sarotherodon melanotheron. 99 Biparental incubation is also a rare case among Cichlidae. At the majority of Chromidotilapines the two parents share the fry. There exist also species at which the female begins incubation then the male takes over: it is the case of Cichlidae gobies of lake Tanganyika. At the oral incubators, often, the males stayed on a zone of nesting at a shallow depth and on a movable substrate (gravel, sand, clay). Each male showing a characteristic color patterns delimits and defends a territory and arranges a nest, where it will try to attract and retain a ripe female. The shape and the size of the nest vary according to the species and even according to the populations within the same species (Figure 170 below). It is often about an arena social organization of reproduction. The females which live in band near the surface of reproduction come only for briefs stays on the arenas. Going from one territory to another, they are courted by successive males until the moment when, stopping above the cup of a nest, they form a transitory couple. After a parade of sexual synchronization (Figure 171, p. 220), the female deposits a batch of eggs, the male immediately fertilizes them by injecting its sperm on eggs in suspension in water, then the female is turned over and takes them in the mouth to incubate them. This very short operation can be started again, either with the same male, or with another male in a nearby territory. At Haplochromines, the anal fins present a spot mimicry an egg to lure the females. It is about successive polygyny and polyandry. Finally, the female moves away from the arena where the males remain confined and carries in mouth the fertilized eggs which it will incubate in sheltered zones. Photo W. Nests of Tilapia zillii (Liberia) [© Y. Fermon].

A

B Figure 170. Nest of A: Oreochromis niloticus; B: Oreochromis macrochir.

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A

B

C

D

E

F

G

H

I

Figure 171. Courtship and spawning in a mouthbrooder Cichlidae, Haplochromis burtoni from Lake Tanganyika. The male is gray. A and B: The female lays eggs while the male remains close to; C: After laying a few eggs, the female quickly turns; D: The female is preparing to collect the eggs before the male has had time to fertilizers; E: Collection of eggs per female, F: The male spreads his anal fin to the female and it shows the ocelli; G and H: The female egg in the mouth, trying to collect these ocelli and closer to the orifice of the male genital ejaculates at the time; I: The female begins to lay a new string of eggs. The entire sequence is repeated several times. The hatching takes place in the mouth of female 4 to 5 days after fecundation, and the vitelline vesicle is completely resolved at the age from 11 to 12 days (Figure 174, p. 222). The duration of this phase depends mainly on the temperature. As soon as the vitelline vesicle is resolved and that the alevins are able to take exogenic food, the female lets escape from the mouth a cloud of juveniles which is directed compared to the mother and takes refuge in its mouth with the least danger and the call of its movements (Figure 172, p. 220).

A

B

Figure 172. Mouthbrooding. A: The juveniles come in the mouth of their mother when any danger. B: The juveniles in the mouth of their mother.

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Subsistence fishfarming in Africa

Females visit the nests  to lay their eggs

In breeding season,  males build their nest Mouthbrooding  incubation by females

Non breeding adults live in  open water

First fry live in group near the mother

Then, they live alone in group Separation of fish  and habitat  selection

Light background

and down deeper and deeper as they grow

They seek later  sandy and muddy  areas

mud

sand

Figure 173. Example of the life cycle of a maternal mouthbrooding tilapia. When the alevins reach a size of 9 - 10 mm, they are freed definitively from their mother. This one releases them out of not very deep water, on the edges, where they are organized in group and continue their growth. The whole of the cycle is summarized in Figure 173, p. 221. A female in good condition can reproduce at intervals from 30 to 40 days when the temperature is of 25 with 28°C. The same female can produce 7 to 8 spawn per year, but all the females of a batch are far from also frequently reproducing.

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4 days after fertilization

7 days

8 days

Embryo

1 mm 5 days

Substrat spawners

Mouthbrooders

1 mm

Juveniles Larvae

3 days

10 days

Figure 174. Different stages in mouthbrooders.

Figure 175. Comparison between fry of substrate spawners and mouthbrooders.

The number of eggs and alevins which a female can contain in its mouth varies according to its size and the species. The record is undoubtedly held by Oreochromis mossambicus which reached the size of 35 cm with 4 000 eggs. For Sarotherodon melanotheron, the eggs of ocher yellow color and slightly pear shaped, reach 3 mm in diameter. They are incubated by the male. The alevins at hatching are 5 mm long and 9 mm when the vitelline vesicle are resorbed.

II.3.3. THE GROWTH The mode of reproduction and parental care has an influence on the size of the embryos and their development. In general, from the physical constraint, the mouthbrooders can accommodate only one limited number of eggs in the oral cavity (Figure 175 above). According to the species, one can note that the maximum size and the size at sexual maturation vary: the fish of the great lakes mature with a larger length and grow until a size more important than those of the lagoons, ponds or rivers (Table XLIII, p. 223, Figure 176 and Figure 177, p. 224). In lake, the size of maturation and the maximum length of the males and females do not differ. On the other hand, in the small over-populated fields or stretches of water, the males grow more quickly than the females whose size of maturation is lower than that of the males. This sexual dimorphism of growth can be connected to the mode of parental care. As soon as the individuals reach the age of maturity (1 to 3 years according to the sex and the field), the male individuals present a growth definitely faster than the females and reach a definitely higher size. That can be understood insofar as the males must establish a territory of reproduction and defend it. For the substrate spawners, this difference is, as that gets along, less important. For the mouthbrooders, the male is generally more dominating that its length is large. Each time one introduces a new male into the field, the males keep a hierarchical basis and preserved this hierarchy until the arrival of the new intruder. What makes the dominant? It takes the territory best placed and supervises it highly, attacking any male passing in the vicinity and courting the females. It will thus invest energy in the defense of its territory at the expense of its growth compared to the other males. However, the growth of the males will remain higher than that of the females. The fish in poor environmental condition mature with a size smaller than those which are in good condition. If one finds individuals in a state of reproduction all the year, there exist nevertheless peaks of reproduction which coincide with the two rainy seasons in equatorial region or at the single rainy season under other latitudes. Moreover, the growth of Oreochromis niloticus is extremely variable from one field to another, which suggests that the maximum size is more dependant on the environmental conditions than of possible genetic differences. For example in the lake Chad in

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Table XLIII. Size at sexual maturation, maximale size and longevity of different species of tilapia. Species Alcolapia grahami Oreochromis aureus Oreochromis esculentus

Oreochromis leucostictus

Oreochromis lidole Oreochromis mortimeri

Oreochromis mossambicus

Oreochromis niloticus

Oreochromis rukwaensis Oreochromis saka Oreochromis shiranus shiranus Oreochromis shiranus chilwae Oreochromis squamipinnis Oreochromis variabilis Sarotherodon galileus Tilapia mariae

Tilapia zillii

Location Lake Magadi Lake Kinneret Lake Victoria Lake Victoria, Kavirondo Gulf Lake Victoria, Jinja Lake Victoria, Mwanza Aquarium Pond Lake Naivasha Lake Edward Lake George Lake Albert Lagon, Lake Albert Pond in Ouganda Pond in Kenya Lake Malawi Lake Kariba Lower Malolo Upper Malolo Egypte Lake Sibaya South Africa Aquarium Egypt Lake George Lake Rudolf Crater, Lake Rudolf Lake Edward Lake Baringo Lake Albert Lagon, Lake Albert Lake Rukwa Lake Malawi Lake Malawi Lake Chilwa Lake Malawi Lake Victoria Lake Kinneret River Sokoto Nigeria, river Osse River Jamieson Lake Kariba Lake Kinneret Pond in Egypt Lake Naivasha Aquarium

Typical / Dwarf D T T

Size at maturation (mm) 25 190 230

Maximale size (mm)

Longevity (years)

100 315 375

5 10

T

230

330

7

T T D D T T T T D D D T T T D T D T D T T T D T T T D D T T T T T T D T D T T T D D

225 240 105 164 180 210 140 260 100 120 70 285 300 180 90

340 325

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Mean weight (g) for fish less than 20 cm length

180

G

R

170 160

E 150

D A

C

140

K 130

T 120

B

110 100

0 2

4

6

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42

Maturation size (cm)

Figure 176. Relationship the weight of fish of 20 cm and the size of maturation for Oreochromis niloticus for several geographic location. R: Lake Turkana; A: Lake Albert; G: Lake George; E: Lake Edward; D: Lake Katinda; C: Lake Chanagwora; K: Lake Kijanebalola; T: Lagoon Tonya of lake Albert; B: Lagoon Buhuku of lake Albert. 10 5

Pond Kijansi

0 15 10

●

●

x

x

Maturation size

Lagoon Buhuku

5 0 20 15

Lake Kijanebalola

Fréquency

10 5 0 35 30

Lake George

25 20 15 10 5 0 20 15

Lake Turkana

10 5 0

0 2 4

6

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66

Total length (cm)

Figure 177. Size class of Oreochromis niloticus according several geographic location.

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Mariout (Egypt)

Lake Kinneret

40

Tg Oau

30 20

Chad

On Tg Tz

Tz

On

Tg Tz

Oau

10 0

Total length (cm)

Oa

Barotse

40

Oa

Kafue (1)

Tr Oma

Kafue (2)

m f Oa m f Oma

Tr Oma

30 20 10 0

Lake Victoria

Lake Malawi

40

Ol Osa Osh

30 20

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Os Ov

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Figure 178. Comparison of growth rate for different species in natural field by locality. Oa: Oreochromis andersonii; Oau: O. aureus; Oe: O. esculentus; Ol: O. lidole; Oma: O. macrochir; Omo: O. mossambicus; On: O. niloticus; Osa: O. saka; Osh: O. shiranus; Ov: O. variabilis; Sg: Sarotherodon galileus; Tr: Tilapia rendalli; Tz: T. zillii. 40

1: Incomati, Limpopo 2: Dam of Doordraai 3: Dam of Dam 4: Lake Sibaya

35 30

3 1

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Standard length (cm)

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2 4 5 6 1: Kafue 2: Lake Montasoa 3: Lake Itasy 4: Lake Liambezi 5: Lake Kariba 6: Lake Alaotra 4

5

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7

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1: Lake Albert 2: Lake Itasy 3: Lake Chad 4: Lake Montasoa 5: Lake Mariout 6: Lake Aloatra

10 5

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15

1: Lake Itasy 2: Kafue 3: Lake Aloatra

1 2

C 1: Lake Chad 1978 2: Lake Chad 1980 1 3: Lake Mariout 2 3

1: Lake Victoria 2: Lake Chad 3: Niger 4: Lake Mariout 1 2 3

4

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Figure 179. Comparison of growth rate for different species in natural field by species. A: Oreochromis mossambicus; B: O. niloticus; C: O. macrochir; D: Tilapia rendalli; E: T. zillii; F: Sarotherodon galileus.

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Uganda, O. niloticus reaches 30 cm at the end of 3 years whereas in the lake Mariout in Egypt, 5 years are necessary to arrive at the same size. It is noted that, in the same field, the growth of O. niloticus is generally higher than that of other species of tilapia for long time (Figure 178 and Figure 179, p. 225). It reaches 300 to 500 g in 8 months, O. leucostictus 300 g, Tilapia zillii 250 to 400 g. It is of a maximum of 3 g/day under optimal conditions. There exist other piscivorous species of Cichlidae, which are used in polyculture for the control of the populations of tilapia. ÖÖ The group of “green” Hemichromis. It is about a complex of species with two major species: H. elongatus and H. fasciatus. The other species of the genus belongs to the group of Hemichromis “red” were also tested but without success because of their rather omnivorous then piscivorous. ÖÖ The fish of the genus Serranochromis, which are the large predatory ones of Southern and East Africa. ÖÖ The tilapia are: ÖÖ Robust fish, ÖÖ Highly plastic and adapt to environnemental conditions, ÖÖ With elaborated parental care, ÖÖ They are opportunistic in terms of diet.

III. THE BIOLOGY OF SILURIFORMES OR CATFISH More known under the name of catfishes, Siluriformes (Siluroidei more precisely) are an important group for fishfarming. Their worldwide production (more than 300 000 tons/year) is currently at the fourth rank of the species cultivated out of fresh water after carps and other Cyprinidae, Salmonidae and the tilapia. With their great diversity of forms and biological characteristics, Siluriformes, represented by more than 2500 described species, can contribute to the valorization of the aquatic resources through diversified systems of production. Today, if the farming of some species of Siluriformes already emerged on a level economically significant of fishfarming production, the potential offered by the biological diversity of this group for the aquaculture remains still largely ignored and needs a constant research effort. In Africa, only few species were used, mainly of the family of Clariidae. However, knowledge of the biology of these species remains still scattered for the majority. But, several can be used as species of supplements and/or control of the populations while bringing some more weight produced in the ponds.

III.1. THE CLARIIDAE Few studies was undertaken on biology Clariidae African used in fishfarming. The data thus remain scattered.

III.1.1. THE TAXONOMY The Clariidae are distinguished from other Siluriformes by the absence of a dorsal-fin spine, the very long dorsal and anal fins, the eel-shaped body, and the presence of four pairs of barbels as well as of a suprabranchial organ, formed by outgrowths of the second and fourth gill arches, which enable these fishes to practice aerial respiration. Several species, in particular those of the genera Clarias and Heterobranchus, play an important role in fishery and fishfarm. Two species are presented in Appendix 05 p. 272. The genus Clarias is characterized by the presence of a single, long dorsal fin that extends to caudal-fin base. The adipose fin is absent (except in one species with a reduced adipose fin). Vertical fins are not confluent. Body is more or less elongate. Head is flattened. Lateral cephalic bones are

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contiguous. Eyes are small, with a free margin. More than 35 described species of Clarias are found in Africa. The genus Heterobranchus is characterized by the presence, between the rayed dorsal and the caudal fin, of a large adipose fin supported by prolonged neural spines. Head is flattened. Lateral cephalic bones are contiguous. Eyes are small, with a free margin. Only, 5 species are known.

III.1.2. THE FEEDING HABIT

Few studies have focused on the nutritional needs of Clariidae, in particular for Clarias gariepinus and to a lesser extent still of Heterobranchus longifilis in natural environment. The rare studies carried out show a similarity in the cover of the general needs for the two species. Clarias gariepinus feeds on the bottom and are omnivorous. He eats insects, crabs, plankton, snails and fish but also of young birds, dead bodies, plants and fruits, the diet is variable according to the size. Other Clariidae are all, generally, according to knowledge on their food, omnivores. Several species have, however, a tendency to feed on fish mainly. For Heterobranchus longifilis, the first food catch of alevins is carried out as of the 2 days age, whereas the vitelline vesicle is not yet entirely resorbed. At this stage, the alevins, whose width of the mouth is from approximately 1 mm, are already able to eat planktonique preys of big size. The diet, primarily zooplanktonophagous until the age of 5-6 days, tends thereafter to diversify gradually with the incorporation of insects of increasing size, mainly of larvae of chironomids. At this stage, one also finds, in the stomach contents, shells of gastropods, organic detritus, remains of plants, and seeds, who represent the evolution of the diet into that of the adult, considered like an omnivore with carnivorous tendency. The alevins are feed continuously day and night, without an unspecified rhythm in the food catch not being highlighted. Clariidae are primarily night fish.

30

E T°

70 60

20 50

40 30

P 10

20

FR

10

Rainfall (cm) and Temperature (°C)

Hatching and relative fecundity (%)

80

0 J

F

M

A

M

J

J

A

S

O

N

D

Mois

Figure 180. Relative Fecundity (% of total weight), % of hatching (% total eggs) of Clarias gariepinus, monthly average rainfall and average temperature. Brazzaville.

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III.1.3. THE REPRODUCTION

The size of the first maturation ranges between 40 and 45 cm for the females and between 35 and 40 cm for the males for Clarias gariepinus. The eggs are greenish. Incubation is approximately 33 hours at 25°C. Oviparous animals, the reproduction ocurs during the rainy season (Figure 180 below). The fish make lateral migrations in the flooded plains to reproduce then return in the lakes or major beds of the rivers. In the majority of the African countries, the cycle of reproduction of the catfish begins at the beginning of the rainy season. The final stimulus of the spawning time seems to be associated with the rise of water and the flood of the marginal zones. During the spawning time, large groups of male and female catfishes adult concentrate at the same place, in water at depth often lower than 10 cm, in edge of lakes or calm water. The African catfish spawns in captivity on a large variety of substrates, including fibers of sisal, sheets of palm tree and stones.

A

B

C

E

D Figure 181. Courtship in Clarias gariepinus. A: The male (in gray) approach the female; B and C: The male surrounded the head of the female and keep it firmly; D: The sperm and egg cells are released into the environment and the females scatters them by movements of tail; E: The couple rests.

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1 mm

36 h

1 mm

Incubation

48 h

1 mm 1 mm

1 mm

Hatching

6 j

1 mm

12 h

9 - 12 j

1 mm 1 mm

24 h

Figure 182. First stages of development for Clarias gariepinus. v

rd J5

v

ed rc

J3

J4 J6

J3

ea

J5 bp

ed rc

J4 ea aa

rd J6

ra

bpe

bp

J7

J8

J7 bpe J8 5 mm

ra J10 5 mm

J10

J14

J17

A

J14

J17

B Figure 183. Several stages of larval development until 17 days. A: Clarias gariepinus; B: Heterobranchus longifilis. aa: adipose fin start; bp: burgeon of the pectoral; bpe: burgeon of the pelvic; ea: start of the anal rays; ed: start of the dorsal rays; ra: anal rays; rc: caudal rays; rd: dorsal rays; v: vesicles.

Subsistence fishfarming in Africa

229

During the parade, which can last several hours, the female of the catfish deposits its eggs by small groups. The courtship is preceded by fighting of males. The couples are isolated. The male puts itself in U around the head of the female. The eggs and sperm are released; then, followed by movements of its tail, the female scatters eggs on an important surface. The couple rests several minutes after the spawning (Figure 181, p. 228). The partner fertilizes at the same time each group of eggs by releasing a cloud of milt above eggs. The eggs adhere finally to the submerged vegetation. In captivity, much of eggs are destroyed by the violence of the blows of tail. After the spawning time, the group of catfishes turns over out of deeper water. There is no parental protection for eggs. After a few weeks, the catfish produces a group of eggs again and prepares with a new spawning time. One second spawning time will be caused by the rains or a new flood. Several spawning times can follow one another thus the same year. The eggs hatch after 24 to 36 hours, according to the temperature of water. The larvae, destined for this stage vesicled larvae, hide in the vegetation. The fry and fingerlings of African catfish are difficult to find in nature. It is probably due to the strong mortality of eggs and the larvae. There is no parental care except the choice of the site of spawning. The development of eggs and the larvae is fast and the fingerlings are free 48 to 72 hours after fecundation (Figure 182 and Figure 183, p. 229). The fingerlings remain in the flooded zones and will migrate when they reach 1.5 to 2.5 cm length. For Heterobranchus longifilis, the eggs are with a broad adhesive disc. Their incubation is carried out in stagnant water and with the darkness. To 27 - 29°C, the hatching occurs 24 to 28h after fecundation.

III.1.4. THE GROWTH Growth rates appeared very promising. Thus all the studies on large Clarias and Heterobranchus give almost linear growth beyond the age of one year (Figure 184 below). For Heterobranchus longifilis, the fish reached on average 900 g in 6 months starting from an average weight of 25 g, during tests in freshwater ponds. Between 100 and 500 g, the rate of growth exceed 5 g/day. For Clarias gariepinus, the fish reached 500 to 1000 g in 8 months.

140

Ln Cg

110 100

Hl

600

Hl

90 80 70

Cs

Cg

60 50 40

500

Cg

400 300 200

30 20

100

10 0

800 700

120

Body weitgh (g)

Standard or total length (cm)

130

50 0

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17

Age (years)

0

10 28 56 84 112 140 168 196 224 254

Days

Figure 184. Compared growth of several African fish species. A: According the size; B: According the weight. Cs: Clarias senegalensis; Cg: Clarias gariepinus; Hl: Heterobranchus longifilis; Ln: Lates niloticus.

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Subsistence fishfarming in Africa

III.2. THE CLAROTEIDAE AND AUCHENOGLANIDIDAE These catfishes are characterized by the presence of two to four pairs of barbels, well developed pectoral-fin spines, a moderately or strongly developed adipose fin, and a medium-sized anal fin. Mouth is supported dorsally by the premaxilla and part of the maxilla Other catfish used in fish farming, we may note the fish of the genus Chrysichthys and the species Auchenoglanis occidentalis (Photo X, p. 232). Before under the same family, these genera have been put in two distincts families.

III.2.1. THE GENUS CHRYSICHTHYS From the family of Claroteidae, the genus Chrysichthys is characterized by the presence of four barbels; 6 (rarely 5 or 7) branched dorsal-fin rays preceded by a very short first spine and a well developed second spine, weakly denticulate along posterior margin; a small or medium-sized, never ossified, adipose fin (its base shorter than head width); pectoral fins with 8-11 branched rays preceded by a strong spine which is distinctly denticulate along posterior margin; pelvic fins inserted at about mid-length of body, with 1 spine and 5 soft rays; a medium-sized anal fin with 3 to 6 spines and 6-12 branched rays; and a deeply forked caudal fin. Eyes are large, positioned laterally, their margin free. Body is moderately elongate, 4-6 times longer than deep. Chrysichthys, more known under the local name of “mâchoiron”, is a fish very appreciated in Côte d’Ivoire and West Africa in general. The many traditional receipts based on “mâchoiron” in the local restaurants (maquis) illustrate the attachment to the festive character of these species. It is easy besides to observe that the largest sales take place the day before the great festivals. The name of “mâchoiron” includes three species of the genus Chrysichthys: C. maurus, C. nigrodigitatus and C. auratus. The distinction between Chrysichthys maurus and C. auratus is not always easy because, for individuals of comparable size, the interspecific morphological differences are tiny whereas intraspecific variability can be very large in particular according to the seasons. On the other hand, the distinction of these two species with C. nigrodigitatus is easy because of its larger size and its rather silver gray coloring, whereas its yellowish for C. maurus and C. auratus. The “mâchoirons”, benthic fish, feed mainly, at the adult stage, of organic detritus and invertebrates: larvae of insects (chironomids, dipters), planktonic crustaceans, molluscs. On the other hand the fingerlings, until the size of 15 cm, seem to feed on zooplankton primarily. Chrysichthys are robust species resisting well to handling and able to temporarily support weak partial oxygen levels.

■■ CHRYSICHTHYS MAURUS

In wild, C. maurus has a relatively slow growth, it reaches approximately 12 cm (more or less 25 g) in one year. When it is rise in pond with a density of 3 fish per m2 and feed with an artificial food to 33% of proteins, C. maurus passes from 11 g to 200 g in 12 months. C. maurus can reproduce from 10 months age. The size of small mature individuals is from 9 to 11 cm in the rivers of Côte d’Ivoire. In wild, the reproduction of C. maurus is seasonal. Ovocytes of small diameter (100 - 150 µm) can be observed at the beginning of the great rainy season (either in April - May). The arrival of continental freshwater and the fall of the temperature of water (passing then to 26 - 29°C) seem to have an influence on the beginning of the process of reproduction of this species. The activity of spawning begins in June and is spread until November - December. During the dry season, as from January, the couples still in reproduction are rare. For the mating and the deposit of eggs, this species seeks crevices (rocks, deadwood, bamboos…). The parents generally remain in the nest with alevins until the resorbtion of their vitelline vesicle. The sexual dimorphism is very marked: the mature male is recognized by a broader head and the female by a plumpness of the abdomen and a bulge of the urogenital papilla. Relative fecundity is about 15 to 20 ovocytes per g of weight of female. The same female produces only one clutch each year.

Subsistence fishfarming in Africa

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■■ CHRYSICHTHYS AURATUS The biology of C. auratus seems very close to that of C. maurus but with a definitely lower growth. This species is not of thus any fishfarming interest.

■■ CHRYSICHTHYS NIGRODIGITATUS

In wild, C. nigrodigitatus reaches 18 cm (fork length) in one year, 24 cm in two years and 30 cm in three years. Studies showed that raised out of basin, it spent eleven months to pass from 15 g (11 cm) to 250 g (26 cm). In a wild state, C. nigrodigitatus in general reproduces from the size of 33 cm (3 years old) with a behavior similar to that of C. maurus (search for receptacle of spawn by the pair). The relative fecundity of this species is close to that of C. maurus. It is given, on mean, a value of 15 ovocytes per g of weight of female, with extreme values of 6 and 24. The hatching intervenes 4 to 5 days after at the temperature of 29 - 30°C by giving larvae from 25 to 30 mg equipped with an important vitelline bag which reabsorbs gradually in ten days. They reach 350 - 400 g into 8 to 10 months. There exists in the adult females a progressive and synchronous development of the gonads corresponding to the reproductive season well marked. The spawning begin at the end of August and their frequency is maximum between September and October (more than 50%). One observes then a fall around at the end of November and the activity of spawning is completed in December. However, it should be noted that if the majority of the spawnings is located regularly between September and November, the annual maximum moves appreciably according to the years.

A

B

C Photo X. Claroteidae. A: Chrysichthys nigrodigitatus [© Planet Catfish]; B: C. maurus [© Teigler - Fishbase]; Auchenoglanididae. C: Auchenoglanis occidentalis [© Planet Catfish].

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III.2.2. THE GENUS AUCHENOGLANIS From the family of the Auchenoglanididae, the genus Auchenoglanis is characterized by its slightly elongate body, three pairs of barbels (one maxillary and two mandibular) and the position of the anterior nostril on upper lip. Dorsal fin with 7 branched rays preceded by 2 spines, the first small, the second strong and denticulate; adipose fin originating shortly behind the dorsal; pectoral fins with 9 branched rays preceded by a strong spine; pelvic fins well developed, with 6 rays, 5 of them branched; anal fin medium-sized, with 6-8 branched rays; caudal fin emarginate. This species has been tested in Côte d’Ivoire at Bouaké. Growth rates have been quite low and the test was not renewed.

III.3. THE SCHILBEIDAE

The Schilbeidae (a catfish family found in Africa and Asia) are characterized by a dorso-ventrally flattened head, a rather short abdomen, a laterally compressed caudal region, and an elongate anal fin (Photo Y below). Dorsal fin is short, sometimes absent. Pectoral fins are provided with a spine (as also the dorsal fin of most species). Three or four (depending on species) pairs of barbels are found around mouth. The Schilbeidae are moderately good swimmers with laterally compressed bodies, as opposed to the majority of bottom-living siluriform fishes which are anguilliform or dorso-ventrally flattened. Five genera have so far been recognized in Africa: Parailia, Siluranodon, Irvineia, Schilbe and Pareutropius. The three first genera have only a low economic value because of their small size. However, some species of the genera Irvineia and Schilbe may reach large size (50 cm or more) are very appreciated. For Schilbe mandibularis, the size of the first sexual maturity presents a variation along the river (upstream, lake and downstream) for the two sexes. It is slightly weaker in the males than in the females (12.3 cm compared with 14.8 upstream and 14.8 against 18.1 cm downstream). The relative data with the evolution of sexual maturity and the gonado-somatic ratio reveal a seasonal cycle of reproduction distinct. The species reproduces in rainy season from April to June then from August to October. The maximum activity of reproduction occurs from April to June, corresponding to the peak of pluviometry. The sexual rest occurs during the dry season, from December to March. Average relative fecundity reaches 163600 ovocytes per kg of body weight, with a minimum of 15308 ovocytes and a maximum of 584593. The diameter of the ovocyte at the spawn is approximately of 1 mm. A negative effect of the lake environment on certain biological indicators of the reproduction (size of the first sexual maturity, sex-ratio, average body weight and fecundity) was highlighted. This influence of the lake could be due to the strong pressure of fishing which is exerted there. The fish of the genus Schilbe become piscivorous towards 13 - 14 cm TL. They are fish usable for the control of the populations of tilapia.

III.4. THE MOCHOKIDAE

All representatives of this family have a scaleless body and three pairs of barbels, one maxillary and two mandibular pairs, except in some rheophilic forms in which the lips are modified into a sucking disk. Nasal barbels are absent. First dorsal fin have an anterior spinous ray, adipose fin is large and sometimes rayed. First pectoral-fin ray is spinous and denticulate. A strong buckler present on head-nape region. Eleven genera and nearby 180 species are known (Photo Z, p. 234). Several species of the genus Synodontis can reach a large size (more than 72 cm) and represent a clear commercial interest. Some could be used as species of complements for polyculture.

Photo Y. Schilbeidae. Schilbe intermedius [© Luc De Vos].

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A

B Photo Z. Mochokidae. A: Synodontis batensoda [© Mody - Fishbase] B: Synodontis schall [© Payne - Fishbase].

IV. THE OTHER FAMILIES Other fish have been tested and needs tests in fishfarming.

IV.1. THE CYPRINIDAE

It is the family of the Carps which are usually used in fishfarming. The fish of the family Cyprinidae have a body covered with cycloid scales and a head naked. All rayed fins are well developed, but adipose fin is absent. Mouth is protrusible, lacking teeth. Sometimes one or two pairs of more or less well developed barbels are present. Lower pharyngeal bones very well developed, are bearing a few teeth aligned in 1-3 rows. In spite of fish of large size observed in Africa, such as for example of the genera Labeo, Varicorhinus and Barbus, few of them were used in fishfarming. It is the case of Labeo victorianus in East Africa and Labeo coubie in Côte d’Ivoire. The major part of the large species are, however, from running water (Photo AA, p. 235).

IV.2. THE CITHARINIDAE The Citharinidae comprise large, deep-bodied and compressed fishes. Following genera, scales are cycloids (Citharinops and Citharinus) or ctenoids (Citharidium). The lips have tiny monocuspid teeth and the mouth is terminal. On the other hand, the very tiny maxillary is toothless. All species have two dorsal fins. The first has 16 to 24 branched rays. The second adipose is quite large. Dorsal fin has 19-24 branched rays. Lateral line is straight, median and complete (47-92 scales). Finally, as a common characteristic of African Characoids, pelvic fins are provided with a scaly process. All species are very high specialised microphagous. They have numerous thin and dense gill rakers. The most remarkable particularity is the presence of a complex suprabranchial organ, which acts like a suction-force pump to concentrate and spin foods before swallowing them. The Citharinidae are not very abundant but they are of great economic importance. All species show a large size. In Chad basin the maximum reported size for Citharinops distichodoides is 840 mm SL and 18 kg weight. The farming of Citharinus citharus was tested but without continuation. It is a herbivore. (Photo AB, p. 235).

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Subsistence fishfarming in Africa

A

B Photo AA. Cyprinidae. A: Barbus altianalis; B: Labeo victorianus [© Luc De Vos, © FAO (drawings)].

A

B Photo AB. Citharinidae. A: Citharinus gibbosus; B: C. citharus [© Luc De Vos].

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A

B Photo AC. Distichodontidae. A: Distichodus rostratus; B: D. sexfasciatus [© Fishbase].

IV.3. THE DISTICHODONTIDAE

The Distichodontidae belong to the order of the Characiformes. This family, which is endemic to Africa, can be identified by the following characters: body elongate (deeper in Distichodus), scales ctenoid, adipose fin generally present, lateral line in mid-lateral position, and teeth well developed. The fish of the genus Distichodus can reach large size (80 cm SL). D. rostratus (76 cm TL, weight of 6 kg) have been tested for fishfarming (Photo AC above). They are mainly herbivorous species.

IV.4. THE CHANNIDAE

The Channidae (formerly Ophicephalidae) are a freshwater fish family occurring in Africa and Asia. The body is elongate and cylindrical in cross-section, covered with cycloid scales. Unpaired fins are long, comprising soft rays but no spines. An accessory breathing organ present in the form of two suprabranchial pharyngeal cavities that permit direct breathing of atmospheric air, allowing the fish to survive for long periods outside the water. A single genus, Parachanna, occurs in Africa; it comprises three species, two of which are found in the area considered here. Parachanna obscura may reach 34 cm SL and he is a piscivorous which is perfectly appropriate for the control of the populations of tilapia in the ponds (Photo AD, p. 236).

Photo AD. Channidae. Parachanna obscura (DRC) [© Y. Fermon].

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Subsistence fishfarming in Africa

IV.5. THE LATIDAE

The Latidae is characterized by the possession of a scaly process at bases of pelvic fins. The shape of the second suborbital bone which is not fused to the preopercle and bears a subocular blade extended backwards into a point. A strong notch is separating the two dorsal fins. In this family, it is the famous Nile Perch called also «Capitaine» in West Africa, Lates niloticus, which was the subject of test in fishpond (Photo AE below). It is this species which have been introduced in lake Victoria in the Sixties. Problems appears, because the cannibalism and the tolerance to the oxygen level. This species can reach 200 cm for a weight of 200 kg. Its growth is quite linear (Figure 184, p. 230 and Figure 185, p. 238). Piscivorous, this species can be used for the control of tilapia in ponds.

IV.6. THE ARAPAIMIDAE

The Arapaimidae, a very ancient family, is characterized by its ovaries lacking oviducts. Today it is represented by only four monospecific genera: one from Australia, Sumatra and Borneo (Scleropages), two from the Guyana and Brazil with the famous Arapaima gigas which can reach 200 cm for a weight of 200 kg, and one, Heterotis, from Africa. Body is laterally compressed and covered with large bony scales of a somewhat horny consistence. Lateral line is complete. Fins is spineless. Maxillary and premaxillary teeth are present but pharyngeal teeth are absent. Only one species occurs in Africa, Heterotis niloticus. A presentation file can be consulted in Appendix 05, p. 274. Its main characteristics are: 99 A rapid growth: 3 g /fish/day or more. Large size, higher than 100 cm length (Figure 185, p. 238). 99 A delicate reproduction. It requires a low depth and herbaceous vegetation. He likes space. The nests of Heterotis niloticus are built in the herbaceous vegetation. They are comparable

Photo AE. Latidae. Lates niloticus [© Luc De Vos].

Subsistence fishfarming in Africa

237

100

90

1

1 80

2

90

2

80 70

5

3

7 70

8 - 9

Standard length (cm)

Standard length (cm)

60

50

40

30 20

1: Nyong 2: Niger 3: Upper Niger

10

50

1

2

3

Age (years)

4

5

  1: Delta of Nil   2: Niger   3: Chari   4: Nil at Khartoum   5: Lake Chad, south   6: Lake Chad, north   7: Lake Kyoga   8: Lake Turkana   9: Lake Albert 10: Lake Nasser

4

40 30 20 10 0

0

10

60

0

A

3 6

B

0

1

2

3

4

5

6

7

8

9

Age (years)

Figure 185. Growth of Heterotis niloticus (A) and of Lates niloticus (B). with small basins measuring approximately 1.2 m in diameter, the center slightly excavated located at approximately 30 cm of depth. The bottom is naked and is generally well flattened. The compact edges are 20 cm thickness at the top and are slightly above water. It are built with the stems of the plants which were removed from the center of the nest. The parents remain near the nest when the eggs are laid. The eggs are rather small (2.5 mms diameter) and orange. They hatch approximately two days after the spawning. The larvae have long branchial filaments, red dark, which are prolonged outside the opercle. They quickly form a swarm of approximately 30 cm in diameter occupying the center of the nest. The 5th or the 6th day, the alevins leave the nest, always in dense swarm, and under the protection of the parents. The juveniles of Heterotis niloticus live in swarm, then in groups whose the number decrease progressively with the growth. 99 It is a microphage - planktivorous but with omnivorous tendency.

ÖÖ The African species are numerous and many may be used in fish farming. However, in the context of livelihoods, will be chosen: ÖÖ A tilapia for the main production; with ÖÖ A piscivorous species. ÖÖ We may also use other species in the pond as an omnivorous species and / or herbivore species. ÖÖ The choice of species will depend on the geographic location of ponds (ichthyoregions).

238

Subsistence fishfarming in Africa

Appendix 04 BIOGEOGRAPHIC DATA

To complete the chapter 03 p. 21, the reader will found here informations on: Table XLIV. Some characteristics of African countries; Table XLV. Characteristics of ichthyoregions and lakes in Africa; Figure 186. Repeat of the map of ichthyoregions and countries; Table XLVI. The ichthyoregions and their repartition by country in Africa; Table XLVII. The genera and species of tilapias recorded by countries in Africa. The user on the field, therefore, by cross, know in each ichtyoregion he is and which species of tilapia is present in its area of intervention.

Subsistence fishfarming in Africa

239

Table XLIV. Some characteristics of African countries. Region: Region in which is the country Population in inhabitants - Surface in km2 - Density in inhabitant / km2 H = Possible Habitats for fisheries in km2 HS = % of possible habitats / surface of the country PM = Mean production between 2000 and 2004 in tonnes Prod = Productivity Icht = Number of ichtyoregions whose a part is included in the country Family, Genera, Species: Number of famiy, genera and species of fish known from the country Country South Africa

Population

Surface

Density

H

HS

Austral

44187637

1219090

36.2

13386

1.1

Algeria

North

33333216

2381741

14.0

Angola

Austral

13115606

1246700

10.5

22976

1.8

Benin

Sub-Sahara

7862944

112622

69.8

2958

2.6

Botswana Burkina Faso

Austral

1639833

581730

2.8

36390

6.3

Sub-Sahara

13902972

274200

50.7

1901

0.7

Burundi

Sub-Sahara

8691005

27834

312.2

2559

9.2

Cameroon

Sub-Sahara

17340702

475442

36.5

19638

4.1

11771

1.9

17.3

Cape Verde

Sub-Sahara

455294

4033

112.9

Central Africa

Sub-Sahara

4303356

622984

6.9

Comoros Congo

Oriental

690948

1862

371.1

Sub-Sahara

3702314

341999

10.8

59212

Congo (DR) / Zaïre

Sub-Sahara

62660551

2344798

26.7

113724

4.9

Côte d’Ivoire

Sub-Sahara

17654843

322461

54.8

4928

1.5

Oriental

768900

23200

33.1 20989

2.1

Djibouti Egypt Erythrea Ethiopia

240

Region

North

78887007

995450

79.2

Oriental

4786994

121320

39.5

Oriental

74777981

1127127

66.3

22048

2.0

Gabon

Sub-Sahara

1424906

267667

5.3

8524

3.2

Gambia

Sub-Sahara

1641564

11295

145.3

2290

20.3

Ghana

Sub-Sahara

22409572

238538

93.9

13871

5.8

Guinea

Sub-Sahara

9690222

245857

39.4

5090

2.1

Equatorial Guinea

Sub-Sahara

540109

28051

19.3

222

0.8

Guinea-Bissau

Sub-Sahara

1442029

36125

39.9

3756

10.4

Kenya

Oriental

34707817

581787

59.7

30576

5.3

Lesotho

Austral

2022331

30355

66.6

6

0.0

342

0.3

Liberia

Sub-Sahara

3631318

111370

32.6

Libya

North

5900754

1759540

3.4

Subsistence fishfarming in Africa

TABLE XLIV (next). Some characteristics of African countries. Region: Region in which is the country Population in inhabitants - Surface in km2 - Density in inhabitant / km2 H = Possible Habitats for fisheries in km2 HS = % of possible habitats / surface of the country PM = Mean production between 2000 and 2004 in tonnes Prod = Productivity Icht = Number of ichtyoregions whose a part is included in the country Family, Genera, Species: Number of famiy, genera and species of fish known from the country Country South Africa

PM

Prod

900

0.7

Algeria

Icht

Families

Genera

Species

3

47

113

224

3

10

16

23

Angola

8800

3.8

3

42

112

294

Benin

28919

97.8

1

46

108

182

Botswana

141

0.0

2

13

37

96

Burkina Faso

8700

45.8

2

29

67

140

Burundi

13081

51.1

2

15

30

57

Cameroon

56500

28.8

3

55

163

498

1

1

1

15000

12.7

2

31

98

320

12

23

28

Cape Verde Central Afric Comoros Congo

25765

4.4

2

50

160

409

Congo (DR) / Zaïre

212000

18.6

6

65

265

1104

Côte d’Ivoire

14366

29.2

Djibouti Egypt

287387

136.9

Erythrea

2

49

113

241

1

5

5

5

4

46

146

230

2

8

9

10

Ethiopia

12518

5.7

3

3

3

3

Gabon

9493

11.1

1

43

106

249

Gambia

2500

10.9

1

36

57

86

Ghana

74700

53.9

2

56

137

262

Guinea

4000

7.9

3

35

91

266

Equatorial Guinea

1015

45.8

2

22

30

38

Guinea-Bissau

150

0.4

1

27

47

78

Kenya Lesotho Liberia Libya

147442

48.2

6

34

75

193

37

63.4

1

5

11

15

4000

116.8

2

37

75

178

3

4

5

8

Subsistence fishfarming in Africa

241

TABLE XLIV (next). Some characteristics of African countries. Region: Region in which is the country Population in inhabitants - Surface in km2 - Density in inhabitant / km2 H = Possible Habitats for fisheries in km2 HS = % of possible habitats / surface of the country PM = Mean production between 2000 and 2004 in tonnes Prod = Productivity Icht = Number of ichtyoregions whose a part is included in the country Family, Genera, Species: Number of famiy, genera and species of fish known from the country Country Madagascar Malawi Mali

Population

Surface

Density

H

HS

18595469

587041

31.7

10555

1.8

Austral

13013926

118484

109.8

27526

23.2

Sub-Sahara

11956788

1240198

9.6

54034

4.4

4777

1.0

21284

2.1

46763

5.8

Morocco

North

33757175

458730

73.6

Mauritius

Oriental

1248592

2040

612.1

Mauritania

Sub-Sahara

3177388

1030700

3.1

Mayotte (France)

Oriental

201234

375

536.6

Mozambique

Austral

19686505

799380

24.6

Namibia

Austral

2044147

825112

2.5

16353

2.0

Niger

Sub-Sahara

12525094

1186408

10.6

44249

3.7

Nigeria

Sub-Sahara

131859731

923768

142.7

58480

6.3

Uganda

Oriental

30262610

241548

125.3

50078

20.7

2416

9.2

13965

7.1

Reunion La (France) Rwanda Western Sahara

Oriental

787584

2504

314.5

Sub-Sahara

8648248

26338

328.4

North

300905

266000

1.1

Austral

7502

410

18.3

Sao Tome & Principe

Sub-Sahara

193413

1001

193.2

Senegal

Sub-Sahara

11987121

196722

60.9

Oriental

83688

455

183.9

Saint-Helena

Seychelles Sierra Leone

Sub-Sahara

6005250

71740

83.7

4771

6.7

Somalia

Oriental

8863338

637657

13.9

12903

2.0

Sudan

Oriental

41236378

2505810

16.5

71237

2.8

Swaziland

Austral

1136334

17365

65.4

33

0.2

Tanzania

Oriental

37979417

945088

40.2

101015

10.7

Chad

Sub-Sahara

10542141

1284200

8.2

152252

11.9

Togo

Sub-Sahara

5681519

56785

100.1

1401

2.5

North

10175014

163610

62.2

10366

6.3

Tunisia

242

Region Oriental

Zambia

Austral

11502010

752612

15.3

73065

9.7

Zimbabwe

Austral

12382920

390757

31.7

3927

1.0

Subsistence fishfarming in Africa

TABLE XLIV (next). Some characteristics of African countries. Region: Region in which is the country Population in inhabitants - Surface in km2 - Density in inhabitant / km2 H = Possible Habitats for fisheries in km2 HS = % of possible habitats / surface of the country PM = Mean production between 2000 and 2004 in tonnes Prod = Productivity Icht = Number of ichtyoregions whose a part is included in the country Family, Genera, Species: Number of family, genera and species of fish known from the country Country Madagascar

PM

Prod

Icht

Families

Genera

Species

30000

28.4

1

24

39

52

Malawi

48391

17.6

5

17

99

402

Mali

101974

18.9

3

31

76

172

1577

3.3

2

14

17

23

20

41

59

5000

2.3

3

35

68

109

7

12

13

11792

2.5

5

38

117

229

Morocco Mauritius Mauritania Mayotte (France) Mozambique Namibia

1500

0.9

5

14

38

82

Niger

33587

7.6

2

24

52

91

Nigeria

166193

28.4

1

57

147

362

Uganda

255116

50.9

5

20

54

226

19

34

50

7071

29.3

3

10

24

68

1

6

7

7

Reunion La (France) Rwanda Western Sahara Saint-Helena

0

0

0

Sao Tome & Principe

5

6

6

49

98

175

18

26

33

Senegal

50431

36.1

2

Seychelles Sierra Leone Somalia Sudan Swaziland

14000

29.3

1

34

81

185

200

0.2

2

12

20

33

52200

7.3

3

27

60

116

70

21.4

1

10

18

35

Tanzania

287443

28.5

6

30

129

449

Chad

75640

5.0

2

31

67

139

Togo

5000

35.7

1

40

79

150

Tunisia

894

0.9

2

10

14

18

Zambia

65334

8.9

4

23

117

352

Zimbabwe

13023

33.2

1

18

42

91

Subsistence fishfarming in Africa

243

Table XLV. Characteristics of ichthyoregions and lakes in Africa. N°: These letters are on the figure 186 next page Drainage basins: Number drainage basins which are in the ichthyoregion Families, Genera, species: Number of families, genera and species of fish known from the ichthyoregion N°

244

Ichtyoregion

Surface area (km2)

Drainage basins

Families

Genera

Species

A

Angolese

520 000

131

34

78

184

B

Lower Guinea

622 000

116

56

176

511

C

Cap

232 000

158

27

49

78

D

Congolese

3 453 000

3

66

228

983

E

Upper Guinea

261 000

116

43

105

286

F

Karroid

1 087 000

77

32

64

107

G

Maghreb

1 588 000

438

22

40

60

H

Madagascar

596 000

364

24

39

52

I

Nilo-soudanian

9 668 000

74

70

218

653

J

Nilo-soudanian (Eburneo-ghanean)

425 000

108

57

148

320

K

Oriental

1 905 000

249

41

88

214

L

Sherbro Island

1 900

24

7

7

9

M

Zambezis

2 949 000

115

46

27

303

N

Zanzibar Island

23 000

1

4

6

12

O

Non defined 1 (Red sea)

61 000

48

15

34

46

P

Non defined 2 (Abyssinia)

956 000

425

31

72

99

Q

Non defined 3 (Namibia 1)

176 000

33

1

1

1

R

Non defined 4 (Namibia 2)

71 000

23

0

0

0

S

Non defined 5 (Sahara)

4 462 000

58

8

10

13

a

Lake Amaramba

3 100

1

7

10

17

b

Lake Chilwa / Lago Chiuta

9 800

1

10

23

39

c

Lake Edward / Édouard

24 000

1

12

24

62

d

Lake Georges

25 000

1

10

20

50

e

Lake Kivu

7 300

1

7

12

38

f

Lake Malombe

2 000

1

8

31

48

g

Lake Naivasha

3 500

1

3

3

3

h

Lake Natron

22 000

1

2

3

9

i

Lake Nyasa / Malawi

128 000

1

13

88

375

j

Lake Ruhondo

1 700

2

4

5

8

k

Lake Rukwa

75 000

1

14

27

60

l

Lake Tanganyika

233 000

1

25

112

371

m

Lake Victoria

309 000

2

16

45

205

Subsistence fishfarming in Africa

Mediterranean sea

G

O

S

Red sea

I

P

E J L

c

B

e

D

N

d m

j l

g h

K

Indian ocean

k i

A f

a b

M

Atlantic ocean

H

Q R

F C

Figure 186. The ichthyoregions (limits in yellow-green) and the countries (limits in red) (Faunafri).

Subsistence fishfarming in Africa

245

South Africa Algeria Angola Benin Botswana Burkina Faso Burundi Cameroon Central Africa Congo Congo DR / Zaïre Côte d’Ivoire Djibouti Egypt Erythrea Ethiopia Gabon Gambia Ghana Guinea Equatoriale Guinea Guinea-Bissau Kenya Lesotho Liberia Libya Madagascar Malawi Mali Morocco Mauritania Mozambique Namibia Niger Nigeria Uganda Rwanda Western Sahara Senegal Sierra Leone Somalia Sudan Swaziland Tanzania Chad Togo Tunisia Zambia Zimbabwe Number of country

246

3 3 3 1 2 2 2 3 2 2 6 2 1 4 2 3 1 1 2 3 2 1 6 1 2 3 1 5 3 2 3 5 5 2 1 5 3 1 2 1 2 3 1 6 2 1 2 4 1 48

Subsistence fishfarming in Africa

1

Zanzibar Island

Zambesis

Sherbro Island

Oriental

Nilo-soudanian (Eburneo-ghanean)

1

1 1

1

Nilo-Soudanian

Madagascar

Maghreb

Karroid

Upper Guinea

Congolese

Cap

Lower Guinea

Country

Angolese

Ichthyoregions

Number ichthyoregion

Table XLVI. The ichthyoregions and their repartition by country in Africa.

1

1

1 1 1

1 1

1

1 1 1 1

1 1

1

1 1 1 1

1

1 1 1

1 1 1 1 1

1

1 1

1

1 1 1

1

1

1 1

1 1

1 1 1 1 1 1

1

1 1

1

1 1

1 1 1 1 1 1 1

1 1 1 1 1 1 1 1

1 2

5

1

6

5

4

6

2

23

6

5

1

1 1 9

1

Lake Victoria

Lake Rukwa

Lake Ruhondo

Lake Malawi/Nyasa

Lake Natron

Lake Naivasha

Lake Malombe

Lake Kivu

Lake Georges

Lake Edward/Édouard

Lake Chilwa/Lago Chiuta

Lake Amaramba

Non defined 5 (Sahara)

Non defined 4 (Namibia 2)

Lake Tanganyika

South Africa Algeria Angola Benin Botswana Burkina Faso Burundi Cameroon Central Africa Congo Congo DR / Zaïre Côte d’Ivoire Djibouti Egypt Erythrea Ethiopia Gabon Gambia Ghana Guinea Equatoriale Guinea Guinea-Bissau Kenya Lesotho Liberia Libya Madagascar Malawi Mali Morocco Mauritania Mozambique Namibia Niger Nigeria Uganda Rwanda Western Sahara Senegal Sierra Leone Somalia Sudan Swaziland Tanzania Chad Togo Tunisia Zambia Zimbabwe Number of country

Non defined 3 (Namibia 1)

Country

Non defined 2 (Abyssinia)

Ichthyoregions

Non defined 1 (Red Sea)

TABLE XLVI (next). The ichthyoregions and their repartition by country in Africa.

1

1

1

1 1

1 1 1 1

1

1

1

1

1

1

1 1

1

1

1

1

1

1 1 1 1

1

1 1 1

1

1 1

1

1 1

1 1

1 1

1

1

1

1

1

2

4

1

1 1 1

6

1

1

10

2

2

2

1

2

1

1

2

3

2

5

Subsistence fishfarming in Africa

247

Table XLVII. The genera and species of tilapias recorded by countries. Number of country South Africa Algeria Angola Benin Botswana Burkina Faso Burundi Cameroon Central Africa Congo Congo DR / Zaïre Côte d’Ivoire Djibouti Egypt Erythrea Ethiopia Gabon Gambia Ghana Guinea Equatoriale Guinea Guinea-Bissau Kenya Lesotho

Country Species

Total Length

N: Native; E: Endemic; I: Introduiced; ?: Not verified

Number of species 106 48 7 2 13 7 8 3 6 30 3 11 27 18 0 8 2 10 10 7 11 12 3 10 22 1 Oreochromis amphimelas 31 1 Oreochromis andersonii 61 10 N N N I I Oreochromis angolensis 23 1 E Oreochromis aureus 46 11 I N I N Oreochromis chungruruensis 23 1 Oreochromis esculentus 50 4 N Oreochromis hunteri 34 2 N Oreochromis ismailiaensis 1 E Oreochromis jipe 54 2 N Oreochromis karomo 30 2 Oreochromis karongae 34 3 Oreochromis korogwe 31 2 N Oreochromis lepidurus 19 2 N N Oreochromis leucostictus 32 6 I N I Oreochromis lidole 38 3 I I I I Oreochromis macrochir 40 25 I N I N I I I I I  ? I Oreochromis malagarasi 30 1  ? Oreochromis mortimeri 48 4 I Oreochromis mossambicus 39 21 N I I I N I I I I I N Oreochromis mweruensis 27 3 N Oreochromis niloticus baringoensis 36 1 E Oreochromis niloticus cancellatus 28 1 E Oreochromis niloticus eduardianus 49 7 N N I Oreochromis niloticus filoa 15 1 E I Oreochromis niloticus niloticus 64 34 I I N I N I I I N N I  ? I N N N Oreochromis niloticus sugutae 20 1 E Oreochromis niloticus tana 35 1 E Oreochromis niloticus vulcani 28 2 N N Oreochromis pangani girigan 33 1 E Oreochromis pangani pangani 34 1 Oreochromis placidus placidus 36 4 N Oreochromis placidus ruvumae 27 2 Oreochromis rukwaensis 36 1 Oreochromis saka 40 3 Oreochromis salinicola 10 1 E Oreochromis schwebischi 33 4 N N N N Oreochromis shiranus chilwae 20 2 Oreochromis shiranus shiranus 42 4 Oreochromis spilurus niger 35 4 N N Oreochromis spilurus percevali 16 1 E Oreochromis spilurus spilurus 19 6 I N N Oreochromis squamipinnis 33 3 Oreochromis tanganicae 45 4 N N Oreochromis upembae 23 2 N Oreochromis urolepis hornorum 27 3 I Oreochromis urolepis urolepis 48 1 Oreochromis variabilis 33 3 N

248

Subsistence fishfarming in Africa

TABLE XLVII (next). The genera and species of tilapias recorded by countries. Number of country Liberia Libya Madagascar Malawi Mali Morocco Mauritania Mozambique Namibia Niger Nigeria Uganda Rwanda Senegal Sierra Leone Somalie Sudan Swaziland Tanzania Chad Togo Tunisia Zambia Zimbabwe

Country Species

Total Length

N: Native; E: Endemic; I: Introduiced; ?: Not verified

Number of species 106 48 17 0 8 10 5 2 7 14 Oreochromis amphimelas 31 1 Oreochromis andersonii 61 10 N Oreochromis angolensis 23 1 Oreochromis aureus 46 11 I N Oreochromis chungruruensis 23 1 Oreochromis esculentus 50 4 Oreochromis hunteri 34 2 Oreochromis ismailiaensis 1 Oreochromis jipe 54 2 Oreochromis karomo 30 2 Oreochromis karongae 34 3 N N Oreochromis korogwe 31 2 Oreochromis lepidurus 19 2 Oreochromis leucostictus 32 6 Oreochromis lidole 38 3 N N I  ? Oreochromis macrochir 40 25 I Oreochromis malagarasi 30 1 Oreochromis mortimeri 48 4 Oreochromis mossambicus 39 21 I N N Oreochromis mweruensis 27 3 Oreochromis niloticus baringoensis 36 1 Oreochromis niloticus cancellatus 28 1 Oreochromis niloticus eduardianus 49 7 Oreochromis niloticus filoa 15 1  ? Oreochromis niloticus niloticus 64 34 N I N Oreochromis niloticus sugutae 20 1 Oreochromis niloticus tana 35 1 Oreochromis niloticus vulcani 28 2 Oreochromis pangani girigan 33 1 Oreochromis pangani pangani 34 1 Oreochromis placidus placidus 36 4 N N Oreochromis placidus ruvumae 27 2 N Oreochromis rukwaensis 36 1 Oreochromis saka 40 3 N N Oreochromis salinicola 10 1 Oreochromis schwebischi 33 4 Oreochromis shiranus chilwae 20 2 N N Oreochromis shiranus shiranus 42 4 I N N Oreochromis spilurus niger 35 4 I Oreochromis spilurus percevali 16 1 Oreochromis spilurus spilurus 19 6 Oreochromis squamipinnis 33 3 N N Oreochromis tanganicae 45 4 Oreochromis upembae 23 2 Oreochromis urolepis hornorum 27 3 Oreochromis urolepis urolepis 48 1 Oreochromis variabilis 33 3

7 6 8 10 7 12 11 1 4 3 31 7 7 3 14 9 E N I N N N N

N

N

I

E N N

N I

N N N N N I N

I

I

I

 ?

I

I N I E N I

N

I

N N

I

N

N N N N N I N N

N

N N N N

I

N

I N N I

I I

E N N E N

N I I

N N

N

N N N N N E N

N

Subsistence fishfarming in Africa

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TABLE XLVII (next). The genera and species of tilapias recorded by countries.

Country

Total Length

Number of country South Africa Algeria Angola Benin Botswana Burkina Faso Burundi Cameroon Central Africa Congo Congo DR / Zaïre Côte d’Ivoire Djibouti Egypt Erythrea Ethiopia Gabon Gambia Ghana Guinea Equatoriale Guinea Guinea-Bissau Kenya Lesotho

N: Native E: Endemic I: Introduiced ?: Not verified

Number of species Tilapia bakossiorum Tilapia baloni Tilapia bemini Tilapia bilineata Tilapia brevimanus Tilapia busumana Tilapia buttikoferi Tilapia bythobates Tilapia cabrae Tilapia cameronensis Tilapia cessiana Tilapia coffea Tilapia congica Tilapia dageti Tilapia deckerti Tilapia discolor Tilapia flava Tilapia guinasana Tilapia guineensis Tilapia gutturosa Tilapia imbriferna Tilapia ismailiaensis Tilapia jallae Tilapia joka Tilapia kottae Tilapia louka Tilapia margaritacea Tilapia mariae Tilapia nyongana Tilapia rendalli Tilapia rheophila Tilapia ruweti Tilapia snyderae Tilapia sparrmanii Tilapia spongotroktis Tilapia tholloni Tilapia thysi Tilapia walteri Tilapia zillii

106 9 18 9 18 27 21 41 16 37 14 24 19 25 40 20 23 12 14 35 9 15  ? 8 11 15 25 18 40 21 45 10 11 5 24 15 22 9 27 27

48 7 2 13 7 8 3 6 30 3 11 27 18 0 8 2 10 10 7 11 12 3 10 22 1 1 E 2 N 1 E 1 E 6 N N N N 2 N N 4 N N 1 E 4 N N N N 1 E 2 N 1 1 E 10 N N N N 1 E 2 N N 1 E 2 I 17 N N N N N N N N N N N 1 E 1 E 1 E 1 2 1 E 4 N N 1 E 5 N N N N 2 N N 24 N N N I N N N I N I 1 E 6 N N N 1 E 10 N N N 1 E 4 N N N N 1 E 2 N 28 N N N N N N I I N N N N N

Species

250

Subsistence fishfarming in Africa

TABLE XLVII (next). The genera and species of tilapias recorded by countries.

Country

Total Length

Number of country Liberia Libya Madagascar Malawi Mali Morocco Mauritania Mozambique Namibia Niger Nigeria Uganda Rwanda Senegal Sierra Leone Somalie Sudan Swaziland Tanzania Chad Togo Tunisia Zambia Zimbabwe

N: Native E: Endemic I: Introduiced ?: Not verified

Number of species Tilapia bakossiorum Tilapia baloni Tilapia bemini Tilapia bilineata Tilapia brevimanus Tilapia busumana Tilapia buttikoferi Tilapia bythobates Tilapia cabrae Tilapia cameronensis Tilapia cessiana Tilapia coffea Tilapia congica Tilapia dageti Tilapia deckerti Tilapia discolor Tilapia flava Tilapia guinasana Tilapia guineensis Tilapia gutturosa Tilapia imbriferna Tilapia ismailiaensis Tilapia jallae Tilapia joka Tilapia kottae Tilapia louka Tilapia margaritacea Tilapia mariae Tilapia nyongana Tilapia rendalli Tilapia rheophila Tilapia ruweti Tilapia snyderae Tilapia sparrmanii Tilapia spongotroktis Tilapia tholloni Tilapia thysi Tilapia walteri Tilapia zillii

106 9 18 9 18 27 21 41 16 37 14 24 19 25 40 20 23 12 14 35 9 15  ? 8 11 15 25 18 40 21 45 10 11 5 24 15 22 9 27 27

24 0 1 0 0 2 0 2 0 0 0 1 1 0 6 0 0 0 1 6 0 0 0 1 2 0 2 0 1 0 14 0 3 0 7 0 0 0 1 15

Species

17 0 8 10 5 2 7 14 7 6 8 10 7 12 11 1 4 3 31 7 7 3 14 9 N

N

N

N

N

N E N

N N

N

N N

N  ?

N

N

N N

N

E N

N

N

N N I N

 ? N N N

I

I N

N N N

N I N

N N

I

N N

N N

N N N

N N

N N

N N N

N N

N

N

I N N N

Subsistence fishfarming in Africa

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TABLE XLVII (next). The genera and species of tilapias recorded by countries.

Species

Number of species Sarotherodon caroli Sarotherodon caudomarginatus Sarotherodon galilaeus galilaeus Sarotherodon galilaeus multifasciatus Sarotherodon galileus borkuanus Sarotherodon galileus boulengeri Sarotherodon galileus sanagaensis Sarotherodon linnellii Sarotherodon lohbergeri

106 22 20 41 17 16 20 16 21 14 26 Sarotherodon melanotheron heudelotii 20 Sarotherodon melanotheron leonensis Sarotherodon melanotheron melanotheron 26 15 Sarotherodon melanotheron paludinosus Sarotherodon mvogoi 24 Sarotherodon nigripinnis dolloi 22 Sarotherodon nigripinnis nigripinnis 20 Sarotherodon occidentalis 31 Sarotherodon steinbachi 15 Sarotherodon tournieri liberiensis 20 Sarotherodon tournieri tournieri 13 Alcolapia alcalicus 10 Alcolapia grahami 20 Alcolapia latilabris 9 Alcolapia ndalalani 8 Danakilia franchettii 10 Konia dikume 14 Konia eisentrauti 10 Myaka myaka 9 Pungu maclareni 14 Stomatepia mariae 15 Stomatepia mongo 14 Stomatepia pindu 13

Number of country South Africa Algeria Angola Benin Botswana Burkina Faso Burundi Cameroon Central Africa Congo Congo DR / Zaïre Côte d’Ivoire Djibouti Egypt Erythrea Ethiopia Gabon Gambia Ghana Guinea Equatoriale Guinea Guinea-Bissau Kenya Lesotho

Country

Total Length

N: Native E: Endemic I: Introduiced ?: Not verified

48 7 2 13 7 8 3 6 30 3 11 27 18 0 8 2 10 10 1 E 4 20 N N N N N N 2 N 1 1 E 2 N E 1 E 1 E 5 2 14 N N N N 1 3 N N N N N N 3 4 N N N 5 1 E 1 2 N 2 2 1 1 1 E 1 E 1 E 1 E 1 E 1 E 1 E 1 E

7 11 12 3 10 22 1 N N N N N

N N N

N

N

N

N N N

N

N N

N

N N

Genera Oreochromis Tilapia Sarotherodon Alcolapia Danakilia Konia Myaka Pungu Stomatepia

252

Subsistence fishfarming in Africa

43 5 2 6 2 4 2 5 3 2 4 14 5 43 2 6 3 4 1 1 19 1 3 8 9 26 1 2 8 4 5 4 2 1 1 2 1 1 1 1 1 3

5 1 7 3 1 2 1 19 1 2 1 2 5 3 6 6 2 5 2 1 1 2 3 3 5 1 5 1 2 1

TABLE XLVII (next). The genera and species of tilapias recorded by countries.

Species

Number of species Sarotherodon caroli Sarotherodon caudomarginatus Sarotherodon galilaeus galilaeus Sarotherodon galilaeus multifasciatus Sarotherodon galileus borkuanus Sarotherodon galileus boulengeri Sarotherodon galileus sanagaensis Sarotherodon linnellii Sarotherodon lohbergeri

106 22 20 41 17 16 20 16 21 14 26 Sarotherodon melanotheron heudelotii 20 Sarotherodon melanotheron leonensis Sarotherodon melanotheron melanotheron 26 15 Sarotherodon melanotheron paludinosus Sarotherodon mvogoi 24 Sarotherodon nigripinnis dolloi 22 Sarotherodon nigripinnis nigripinnis 20 Sarotherodon occidentalis 31 Sarotherodon steinbachi 15 Sarotherodon tournieri liberiensis 20 Sarotherodon tournieri tournieri 13 Alcolapia alcalicus 10 Alcolapia grahami 20 Alcolapia latilabris 9 Alcolapia ndalalani 8 Danakilia franchettii 10 Konia dikume 14 Konia eisentrauti 10 Myaka myaka 9 Pungu maclareni 14 Stomatepia mariae 15 Stomatepia mongo 14 Stomatepia pindu 13

Number of country Liberia Libya Madagascar Malawi Mali Morocco Mauritania Mozambique Namibia Niger Nigeria Uganda Rwanda Senegal Sierra Leone Somalie Sudan Swaziland Tanzania Chad Togo Tunisia Zambia Zimbabwe

Country

Total Length

N: Native E: Endemic I: Introduiced ?: Not verified

24 0 2 9 0 1 0 0 0 0 2 2 6 1 0 0 0 3 0 1 1 1 1 1 1 0 0 0 0 0 0 0 0

17 0 8 10 5 2 7 14 7 6 8 10 7 12 11 1 4 3 31 7 7 3 14 9 N

N N N N

N N

N

N

N N E

N N N

N

N

N N

N N N E

N

N N

E N N N E E

Genera Oreochromis Tilapia Sarotherodon Alcolapia Danakilia Konia Myaka Pungu Stomatepia

43 9 43 6 26 2 1 1 1 1 1

3 2 2 1 3 2 4 3 4 2 1 4 6 1 1 3 1 2 5 4

1 2 3 3 3 1 4 3 1 2 2 4

Subsistence fishfarming in Africa

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254

Subsistence fishfarming in Africa

Appendix 05 FILE OF SPECIES

Are presented here by files, different species more or less commonly in aquaculture. The reader will find the scientific Synonyms, common names french and english, size and maximum weight known in the literature, as well as distribution maps and elements of the biology of these species. File I.

Cichlidae. - Oreochromis andersoni

256

File II.

Cichlidae. - Oreochromis aureus

257

File III.

Cichlidae. - Oreochromis esculentus

258

File IV.

Cichlidae. - Oreochromis macrochir

259

File V.

Cichlidae. - Oreochromis mossambicus

260

File VI.

Cichlidae. - Oreochromis niloticus

261

File VII.

Cichlidae. - Oreochromis shiranus

262

File VIII.

Cichlidae. - Sarotherodon galileus

263

File IX.

Cichlidae. - Sarotherodon melanotheron

264

File X.

Cichlidae. - Tilapia guineensis

265

File XI.

Cichlidae. - Tilapia mariae

266

File XII.

Cichlidae. - Tilapia rendalli

267

File XIII.

Cichlidae. - Tilapia zillii

268

File XIV.

Cichlidae. - Hemichromis elongatus and Hemichromis fasciatus

269

File XV.

Cichlidae. - Serranochromis angusticeps

270

File XVI.

Cichlidae. - Serranochromis robustus

271

File XVII.

Clariidae. - Clarias gariepinus

272

File XVIII. Clariidae. - Heterobranchus longifilis

273

File XIX.

274

Arapaimidae. - Heterotis niloticus

Subsistence fishfarming in Africa

255

File I. CICHLIDAE. Oreochromis andersoni (Castelnau, 1861) Synonyms: Chromys andersoni Castelnau, 1861 - Oreochromis anulerson (Castelnau, 1861) - Sarotherodon andersoni (Castelnau, 1861) - Tilapia andersoni (Castelnau, 1861) - Tilapia kafuensis Boulenger, 1912 - Tilapia natalensis (non Weber)

English name: Three spotted tilapia

Nom français:

© K. Winnemiller Aquaculture: commercial

Fishery: commercial - sport

Ornemental: Max. size: 61 cm TL Max. weight: 4.7 kg Biology: Benthopelagic. May be found in brackish water. Occurs in both river and swamp habitats and is adapted to fairly fast-flowing rivers, preferring slow-flowing or standing water; juveniles remain inshore among vegetation. Forms schools. Mainly diurnal; a detritivore which feeds on fine particulate matter, including algae, diatoms, detritus and zooplankton. Larger individuals also take insects and other invertebrates. Female mouthbrooder. Several countries report adverse ecological impact after introduction.

Distribution: Know from Ngami basin, Okavango River; Cunene River and Mossamedes, Angola; upper Zambezi, Kafue River; middle Zambezi, Lake Kariba.

256

Subsistence fishfarming in Africa

File II. CICHLIDAE. Oreochromis aureus (Steindachner, 1864) Synonyms: Chromis aureus Steindachner, 1864 - Tilapia aurea (Steindachner, 1864): Trewavas, 1966 - Sarotherodon aureus (Steindachner, 1864): Trewavas, 1973 – Tilapia monodi Daget, 1954 Tilapia lemassoni Blache & Miton, 1960 English name: Blue tilapia

French name: Tilapia bleu

© Fishbase Aquaculture: commercial

Fishery: commercial - bait

Ornemental: commercial Max. size: 50.8 cm TL – 37 SL Max. weight: 2.0 kg Biology: Benthopelagic. Maybe found in brackinsh water. Occuring at temperatures ranging from 8°-30°C. Considered as a pest. Forms schools; is sometimes territorial; inhabits warm ponds and impoundments as well as lakes and streams, in open water as well as among stones and vegetation. Feeds on phytoplankton and small quantities of zooplankton. Juveniles have a more varied diet. Maternal mouthbrooder

Distribution: The natural distribution of this species include the Jordan Valley, Lower Nile, Chad Basin, Benue, middle and upper Niger, Senegal River.

Subsistence fishfarming in Africa

257

File III. CICHLIDAE. Oreochromis esculentus (Graham, 1928) Synonyms: Tilapia esculenta Graham, 1928 - Sarotherodon esculentus (Graham, 1928) - Tilapia eduardiana (non Boulenger, 1912) - Tilapia galilaea (non Linnaeus, 1758) - Tilapia variabilis (non Boulenger, 1906)

English name: Singida tilapia

French name:

© Fishbase Aquaculture: commercial

Fishery: commercial - experimental Ornemental: Max. size: 50 cm LS Max. weight: 2.5 kg Biology: Benthopelagic. Occurs at temperatures ranging from 23.0-28.0°C. Tolerant of low oxygen concentrations. Filter feeder. Food consist almost entirely of phytoplankton but also small animals such as insects and their larvae, crustaceans. Maternal moutbrooder.

Distribution: Known from Lake Victoria, Lake Nabugabo, Lakes Kyoga and Kwania, and the Victoria Nile above the Murchison Falls; the Malawa River (Uganda) and Lake Gangu, west of Lake Victoria. This species, which was originally endemic to Lake Victoria, is widely distributed in dams.

258

Subsistence fishfarming in Africa

File IV. CICHLIDAE. Oreochromis macrochir (Boulenger, 1912) Synonyms: Tilapia galilaea (non Linnaeus) - Tilapia nilotica (non Linnaeus, 1758) - Chromys chapmani Castel-

nau, 1861 - Tilapia andersonii (non Castelnau, 1861) - Chromys chapmannii Castelnau, 1861 - Chromys sparmanni Castelnau, 1861 - Tilapia squamipinnis (non Günther, 1864) - Tilapia natalensis (non Weber, 1897) - Tilapia macrochir Boulenger, 1912 - Loruwiala macrochir (Boulenger, 1912) - Sarotherodon macrochirus (Boulenger, 1912) - Oreochromis microchir (Boulenger, 1912) - Tilapia macrochir Boulenger, 1912 - Sarotherodon macrochir (Boulenger, 1912) - Tilapia kafuensis (non Boulenger, 1912) - Tilapia intermedia Gilchrist & Thompson, 1917 - Tilapia sheshekensis Gilchrist & Thompson, 1917 - Tilapia alleni Fowler, 1931

English name: Longfin, Greenhead tilapia

French name: Tilapia noir

© Luc De Vos Aquaculture: commercial

Fishery: commercial - sport

Ornemental: Max. size: 43.0 cm SL Max. weight: Biology: Benthopelagic. Mating territory having a central volcano-shaped mound. Prefers quiet, deep water associated with aquatic vegetation. Occasionally forms schools, is mainly diurnal. Feeds mostly on detritus, (bluegreen) algae and diatoms. Maternal mouthbrooder.

Distribution: Known from Kafue, upper Zambezi, and Congo River systems; introduced elsewhere in Africa and in Hawaiian Islands. Also in the Okavango and Ngami region, Cunene basin, Chambezi and Bangweulu region.

Subsistence fishfarming in Africa

259

File V. CICHLIDAE. Oreochromis mossambicus (Peters, 1852) Synonyms: Chromis mossambicus, Peters, 1852 - Tilapia arnoldi Gilchrist & Thompson, 1917 - Tilapia ka-

fuensis (non Boulenger, 1912) - Chromis niloticus (non Linneaus, 1758) - Tilapia mossambica (Peters, 1852) - Sarotherodon mossambicus (Peters, 1852) - Chromis niloticus mossambicus Peters, 1855 - Chromis dumerilii Steindachner, 1864 - Tilapia dumerilii (Steindachner, 1864) - Chromis vorax Pfeffer, 1893 - Tilapia vorax (Pfeffer, 1893) - Chromis natalensis Weber, 1897 - Tilapia natalensis (Weber, 1897) - Sarotherodon mossambicus natalensis (Weber, 1897)

English name: Mozambic tilapia

French name: Tilapia du Mozambique

© A. Lamboj Aquaculture: commercial

Fishery: commercial - sport

Ornemental: commercial Max. size: 39 cm SL Max. weight: 1.1 kg Biology: Benthopelagic. Highly euryhaline. Grows and reproduces in fresh-, brackish and seawater. Tolerates low dissolved oxygen levels. Considered as a pest. Can be found in quite all kinds of habitat. Form schools. Omnivorous, feeds mainly on algae and phytoplankton but also takes some zooplankton, small insects and their larvae. Juvenile carnivorous/omnivorous, adult tends to be herbivorous or detritus feeder. Large specimen has been reported to prey on small fishes. Maternal mouthbrooder.

Distribution: The natural distribution is of Lower Zambezi, Lower Shire and coastal plains from Zambezi delta to Algoa Bay. Occurs southwards to the Brak River in the eastern Cape and in the Transvaal in the Limpopo system. Widely introduced for aquaculture.

260

Subsistence fishfarming in Africa

File VI. CICHLIDAE. Oreochromis niloticus (Linneaus, 1758) Synonyms: Labrus niloticus Linnaeus, 1758 - Chromis niloticus Günther, 1862 - Tilapia nilotica (Linnaeus, 1758) - Sarotherodon niloticus (Linnaeus, 1758)

English name: Nile tilapia

French name: Tilapia du Nil

© Y. Fermon Aquaculture: commercial

Fishery: commercial

Ornemental: commercial Max. size: 74 cm TL – 39.5 SL Max. weight: 4.3 kg Biology: Benthopelagic. Considered as a pest. Found in all kind of habitats. Diurnal. Feed on phytoplankton and algae. Maternal mouthbrooder.

8 sub-species of Oreochromis niloticus are recorded: O. n. baringoensis, O. n. cancellatus, O. n. eduardianus, O. n. filoa, O. n. niloticus, O. n. sugutae, O. n. tana, O. n. vulcani. Distribution: O. n. niloticus: coastal rivers of Israel; Nile from below Albert Nile to the delta; Jebel Marra; basins of the Niger, Benue, Volta, Gambia, Senegal and Chad. - O. n. baringoensis: endemic to Lake Baringo, Kenya. O. n. cancellatus: Lakes of the Ethiopian Rift Valley, Lake Beseka and the Awash system. O. n. edouardianus: Albert Nile; Lakes Albert, Edward, George, Kivu; River Ruzizi and Lake Tanganyika. Introduced in Lake Victoria. O. n. filoa: Awash system. O. n. sugutae: river Suguta in Kenya. O. n. tana: Lake Tana. O. n. vulcani: Lake Turkana (Rudolf) and arround.

Subsistence fishfarming in Africa

261

File VII. CICHLIDAE. Oreochromis shiranus Boulenger, 1897 Synonyms: Sarotherodon shiranus (Boulenger, 1897) - Sarotherodon shiranus subsp. shiranus (Boulenger, 1897) - Tilapia placida (non Trewavas, 1941) - Tilapia shirana (Boulenger, 1897) - Tilapia shirana subsp. chilwae Trewavas, 1966 - Tilapia shirana subsp. shirana (Boulenger, 1897)

English name:

French name:

© Fishbase Aquaculture: commercial

Fishery: commercial

Ornemental: commercial Max. size: 39 cm SL Max. weight: Biology: Benthopelagic. Found mainly in densely vegetated shallow waters around the lake Malawi. Mainly diurnal; feeds on detritus and phytoplankton. Maternal mouthbrooder.

2 sub-species of Oreochromis shiranus are recorded: O. s. shiranus, O. s. chilwae Distribution: O. s. shiranus: Shire River above the Murchison rapids and its tributaries; Lake Malawi and its tributary rivers, streams and lagoons; upper Shire. O. s. chilwae: Lake Chilwa and its basin in Malawi and Mozambique.

262

Subsistence fishfarming in Africa

File VIII. CICHLIDAE. Sarotherodon galileus (Linneaus, 1758) Synonyms: Sparus galilaeus Linnaeus, 1758 - Tilapia galilaea (Linnaeus, 1758) - Tilapia galilaea galilaea (Linnaeus, 1758) - Tilapia pleuromelas Duméril, 1859 - Tilapia lateralis Duméril, 1859 - Tilapia macrocentra Duméril, 1859 - Chromis multifasciatus Günther, 1903 - Tilapia multifasciata (Günther, 1903) - Tilapia galilaea multifasciata (Günther, 1903) English name: Mango tilapia

French name:

© Fishbase Aquaculture: commercial

Fishery: commercial

Ornemental: Max. size: 41 cm TL – 34 SL Max. weight: 1.6 kg Biology: Demersal. Occasionally forms schools; territorial. Prefers open waters but juveniles and breeding adults are found inshore Feeds on algae and fine organic debris. Bi-parental mouthbrooder.

5 sub-species of Sarotherodon galileus are recorded: S. g. borkuanus, S. g. boulengeri, S. g. galileus, S. g. multifasciatus, S. g. sanagaensis. Distribution: S. g. borkuanus: Saharian oases Borku, Ennedi and Tibesti in northern Chad. S. g. boulengeri: Lower Congo from Malebo (Stanley) Pool to Matadi. S. g. galileus: Jordan system, especially in lakes; coastal rivers of Israel; Nile system, including the delta lakes and Lake Albert and Turkana; central Congo basin, Ubanghi and Uele Rivers; in West Africa in the Senegal, Gambia, Casamance, Géba, Konkouré, Niger, Volta, Mono, Ouémé, Ogun, Cross, Benue, Logone, Shari and Lake Chad. S. g. multifasciatus: Côte d’Ivoire (Sassandra, Bandama, and Comoé Rivers) to western Ghana (Tano River and Lake Bosumtwi). S. g. sanagaensis: known only from the Sanaga River system, Cameroon.

Subsistence fishfarming in Africa

263

File IX. CICHLIDAE. Sarotherodon melanotheron Rüppel, 1852 Synonyms: Tilapia heudelotii Duméril, 1859 - Tilapia heudelotii heudelotii Duméril, 1859 - Tilapia rangii Duméril, 1859 - Tilapia multifasciata macrostoma Pellegrin, 1941 - Sarotherodon melanotheron paludinosus Trewavas, 1983 - Tilapia melanotheron (Rüppell, 1852) - Chromis microcephalus Günther, 1862 - Tilapia microcephala (Günther, 1862) - Melanogenes macrocephalus Bleeker, 1862 - Tilapia macrocephala (Bleeker, 1862) - Tilapia leonensis Thys van den Audenaerde, 1971 English name: Blackchin tilapia

French name: Tilapia à gorge noire

© Y. Fermon Aquaculture: commercial

Fishery: commercial

Ornemental: commercial Max. size: 31 cm TL Max. weight: Biology: Demersal. Primarily in estuaries and lagoons. Abundant in mangrove areas. Potential pest. Forms schools; is mainly nocturnal with intermittent daytime feeding. Feeds on aufwuchs and detritus.

3 sub-species of Sarotherodon melanotheron are recorded: S. m. heudelotii, S. m. melanotheron, S. m. leonensis. Distribution: S. m. heudelotii: Lagoons and estuaries from Mauritania to Sierra Leone. S. m. melanotheron: Lagoons and estuaries from Côte d’Ivoire to Cameroon. S. m. leonensis: brackish areas and freshwaters near the coast of Sierra Leone and western Liberia. Sometimes found in sea.

264

Subsistence fishfarming in Africa

File X. CICHLIDAE. Tilapia guineensis (Bleeker in Günther, 1862) Synonyms: Chromis guineensis Bleeker in Günther, 1862 - Haligenes guineensis Bleeker, 1863 - ?Tilapia affinis Duméril,1858 - ?Chromis latus Günther, 1862 - ?Tilapia lata (Günther, 1862) - ?Tilapia polycentra Duméril, 1858 English name: Guinea tilapia

French name: Tilapia de Guinée, Carpe

© A. Lamboj Aquaculture: commercial

Fishery: commercial

Ornemental: Max. size: 35 cm TL - 28.2 SL Max. weight: Biology: Found also in brackish waters. Benthopelagic. Feeds on shrimps, bivalves, plankton and detritus. Oviparous. Substrate spawner.

Distribution: Known from coastal waters from mouth of Senegal River to mouth of the Cuanza River (Angola), sometimes ascending far up rivers.

Subsistence fishfarming in Africa

265

File XI. CICHLIDAE. Tilapia mariae Boulenger, 1899 Synonyms: Tilapia dubia Lönnberg, 1904 - Tilapia heudeloti (non Duméril, 1861) - Tilapia mariae dubia Lönnberg, 1904 - Tilapia meeki Pellegrin, 1911 - Tilapia melanopleura (non Duméril, 1861) Tilapia microcephala (non Günther, 1862)

French name: Tilapia à 5 bandes

English name: Spotted tilapia

© Fishbase Aquaculture:

Fishery:

Ornemental: commercial Max. size: 39.4 cm TL - 23 SL Max. weight: 1.4 kg Biology: Demersal. May be found in brackish water. Considered as a pest. Live in still or flowing waters in rocky or mud-bottom areas. Consume plant matter. Reache sexual maturity at 1015 centimeters length. Parents prepare nest site on logs, leaves and other debris. The eggs (6003300 per female) are guarded by the parents and hatch in 1-3 days. Parental care of the brood continues until the fish are about 2.5-3.0 centimeters. Substrate spawner.

Distribution: Known from coastal lagoons and lower river courses from the Tabou River (Côte d’Ivoire) to the Kribi River (Cameroon), but absent from the area between the Pra River (Ghana) and Benin.

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File XII. CICHLIDAE. Tilapia rendalli (Boulenger, 1897) Synonyms: Chromis rendallii Boulenger, 1896 – Tilapia sexfasciata Pellegrin, 1900 – Tilapia latifrons Boulenger, 1906 –Tilapia christyi Boulenger, 1915 – Tilapia druryi Gilchrist & Thompson, 1917 – Tilapia kirkhami Gilchrist & Thompson, 1917 – Tilapia mackeani Gilchrist & Thompson, 1917 – Tilapia sykesii Gilchrist & Thompson, 1917 – Tilapia swierstrae Gilchrist & Thompson, 1917 – Tilapia gefuensis Thys van den Audenaerde, 1964 –Tilapia zillii (non Gervais, 1848) - Tilapia melanopleura rendalli (Boulenger, 1897) - Tilapia melanopleura (non Duméril, 1861) - Tilapia lata (non Günther, 1862) - Tilapia melanopleura swierstrae Gilchrist & Thompson, 1917

English name: Redbreasted tilapia

French name: Tilapia à poitrine rouge, carpe

© Fishbase Aquaculture: commercial

Fishery: commercial - sport

© Fishbase Ornemental: commercial Max. size: 45 cm TL Max. weight: 2.5 kg Biology: Demersal. Considered as a pest. Prefer quiet, well-vegetated water along river littorals or backwaters, floodplains and swamps. Form schools; is mainly diurnal. Juveniles feed on plankton. Adults feed mainly on higher plants and also algae, insects and crustaceans. Tolerant of a wide range of temperature and salinity.

Distribution: Know from Senegal and Niger River, Congo River system, Zambezi River system, Lake Tanganyika and Malagarazi. Also known from Shaba, upper Kasaï, Lualaba system, Lake Malawi, Natal, Okavango and Cunene. Introduced elsewhere.

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File XIII. CICHLIDAE. Tilapia zillii (Gervais, 1848) Synonyms: Acerina zillii Gervais, 1848 - Haligenes tristrami Günther, 1859 - Tilapia melanopleura Duméril, 1859 - Chromis andreae Günther, 1864 - Chromis caeruleomaculatus de Rochebrune, 1880 - Chromis faidherbii de Rochebrune, 1880 - Chromis menzalensis Mitchell, 1895 - Tilapia sparrmani multiradiata Holly, 1928 - Tilapia shariensis Fowler, 1949 English name: Redbelly tilapia

French name: Tilapia à ventre rouge

© A. Lamboj Aquaculture: commercial

Fishery: commercial

Ornemental: commercial Max. size: 49 cm TL - 21 SL Max. weight: Biology: Demersal. Occasionally form schools; mainly diurnal. Prefer shallow, vegetated areas. Fry are common in marginal vegetation and juveniles are found in the seasonal floodplain. Herbivorous. Substrate spawner.

Distribution: Found is South Morocco, Sahara, Niger-Benue system, rivers Senegal, Sassandra, Bandama, Boubo, Mé, Comoé, Bia, Ogun and Oshun, Volta system, Chad-Shari system, UbangiUele-Ituri Rivers (Democratic Republic of the Congo), Lakes Mobutu and Turkana, Nile system and the Jordan system. Introduced in several countries.

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File XIV. CICHLIDAE. Hemichromis « vert »: H. fasciatus Peters, 1852 - H. elongatus (Guichenot, 1861) This group included several species but request more taxonomic investigations. Two main species which are regularly confused: H. fasciatus and H. elongatus. Synonyms: H. fasciatus: H. leiguardii Capello, 1872 - ?Hemichromis desguezii de Rochebrune, 1880 - Hemichromis frempongi Loiselle, 1979. H. elongatus: Hemichromis auritus Gill, 1962 English name: Banded jewelfish

French name: Hemichromis rayé

© A. Lamboj Aquaculture: commercial

Fishery: subsistence

Ornemental: commercial Max. size: 25 cm TL - 20.4 SL Max. weight: 0.3 kg Biology: Benthopelagic. Potamodromous. Found in savannah and forests. Feeds on fish, shrimp and aquatic insects; very aggressive and territorial. Substrate spawner.

Distribution: H. fasciatus (in blue on the map). Found from the Nile basin to the East and in Central regions as Lake Chad. Widely distributed from Senegal to Congo. H. elongatus (in red on the map). Found from Sierra Leone to Okavango and Zambezi basins.

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File XV. CICHLIDAE. Serranochromis angusticeps (Boulenger, 1907) Synonyms: Chromys levaillantii Castelnau, 1861- Serranochromis levaillantii (Castelnau, 1861) - Tilapia levaillantii (Castelnau, 1861) - Paratilapia robusta (non Günther, 1864) - Paratilapia angusticeps Boulenger, 1907 - Paratilapia kafuensis Boulenger, 1908 - Serranochromis kafuensis (Boulenger, 1908) English name: Thinface largemouth

French name:

© K. Winnemiller Aquaculture: commercial

Fishery: commercial - sport

Ornemental: commercial Max. size: 41 SL Max. weight: 2.5 kg Biology: Demersal. Occurs in well-vegetated swamps and along the edges of rivers. Also occurs in fast-flowing reaches over sand and rocks. Feeds on small fish, shrimps and insects. A mouthbrooding species.

Distribution: Cunene River system, Okavango River, upper Zambezi, and Kafue Rivers, and Luapula-Moeru.

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File XVI. CICHLIDAE. Serranochromis robustus (Günther, 1864) Synonyms: Chromys levaillantii Castelnau, 1861- Serranochromis levaillantii (Castelnau, 1861) - Tilapia levaillantii (Castelnau, 1861) - Paratilapia robusta (non Günther, 1864) - Paratilapia angusticeps Boulenger, 1907 - Paratilapia kafuensis Boulenger, 1908 - Serranochromis kafuensis (Boulenger, 1908) English name: Yellow-belly bream

French name:

© K. Winnemiller Aquaculture:

Fishery: commercial - sport

Ornemental: Max. size: 56 TL Max. weight: 6.1 kg Biology: Demersal. Found over sandy and vegetated areas as well as over rocky substrates. Feeds on fish and sand-dwelling invertebrates (Ref. 5595). Larger specimens prefer deep main channels and permanent lagoons, whereas smaller fishes occur mainly in lagoons and secondary channels. Oviparous. Breeds in summer, nesting along vegetated fringes of mainstreams. Mouthbrooder. 2 sub-species of Serranochromis robustus are recorded: S. r. robustus, S. r. jallae.

Distribution: S. r. robustus: Found in Lake Malawi and the upper Shire River. Reported from Luongo River, Congo system, Zambia. Translocated to the upper Ruo River in Malawi and also to Swaziland. S. r. jallae: Found in Cunene River, Okovango River, upper Zambezi River, Kafue River, middle Zambezi River including the Luangwa River; Luapula-Moero, Lualaba and Kasai (Congo River system). Translocated to localities in Zimbabwe, to the Limpopo River and Natal, South Africa.

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File XVII. CLARIIDAE Clarias (Clarias) gariepinus (Burchell, 1822) Synonyms: Silurus (Heterobranchus) gariepinus Burchell, 1822 - Clarias syriacus Valenciennes, 1840 - Clarias capensis Valenciennes, 1840 - Clarias lazera Valenciennes, 1840 - Clarias mossambicus Peters, 1852 - Clarias xenodon Günther, 1864 - Clarias macracanthus Günther, 1864 - Clarias orontis Günther, 1864 - Clarias robecchii Vinciguerra, 1893 - Clarias microphthalmus Pfeffer, 1896 - Clarias smithii Günther, 1896 - Clarias guentheri Pfeffer, 1896 - Clarias micropthalmus Pfeffer, 1896 - Clarias longiceps Boulenger, 1899 - Clarias moorii Boulenger, 1901 - Clarias vinciguerrae Boulenger, 1902 - Clarias tsanensis Boulenger, 1902 - Clarias malaris Nichols & Griscom, 1917 - Clarias notozygurus Lönnberg & Rendahl, 1922 - Clarias depressus Myers, 1925 - Clarias muelleri Pietschmann, 1939

English name: North African catfish

French name: Silure, poisson-chat nord africain

© Y. Fermon Aquaculture: commercial

Fishery: commercial minor

Ornemental: Max. size: 170 TL Max. weight: 60 kg Biology: Benthopelagic. OOccurs mainly in quiet waters, but be found quite everywherer. Widely tolerant of extreme environmental conditions. The presence of an accessory breathing organ enables this species to breath air, it can move from place to place with its pectoral fins. Forages at night on a wide variety of prey. Feeds on insects, plankton, invertebrates and fish but also takes young birds, rotting flesh and plants. Migrates to rivers and temporary streams to spawn. It was noted to generate weak electric discharges.

Distribution: Almost Pan-Africa, absent from Maghreb, the upper and lower Guinea and the Cape province and probably also Nogal province. Asia: Jordan, Israel, Lebanon, Syria and southern Turkey. Widely introduced to other parts of Africa, Europe and Asia. Several countries report adverse ecological impact after introduction.

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File XVIII. CLARIIDAE Heterobranchus longifilis Valenciennes, 1840 Synonyms: Heterobranchus laticeps Peters, 1852 - Clarias loangwensis Worthington, 1933 - Heterobranchus platycephalus Nichols & LaMonte, 1934

English name: Vundu

French name: Silure, Vundu

© Y. Fermon Aquaculture: commercial

Fishery: commercial minor

Ornemental: commercial Max. size: 150 cm SL Max. weight: 55 kg Biology: Demersal. Occurs in large deep rivers within the mainstream or in deep pools and lakes. Most active at night, feeding on any available food, including invertebrates and insects when small, fish and other small vertebrates when large.

Distribution: Found from Nile, Niger, Senegal, Congo system, upper and middle Zambezi. Also from Lakes Tanganyika and Edward, Gambia and Benue River, Chad and Volta basins, and the coastal basins of Guinea to Nigeria.

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File XIX. ARAPAIMIDAE Heterotis niloticus (Cuvier, 1829) Synonyms: Clupisudis niloticus (Cuvier, 1829) - Sudis niloticus Cuvier, 1829 - Sudis nilotica Cuvier, 1829 - Sudis adansonii Cuvier, 1829 - Heterotis nilotica (Cuvier, 1829) - Heterotis adansonii (Cuvier, 1829) - Heterotis ehrenbergii Valenciennes, 1847 - Heterotis adansoni Valenciennes, 1847

English name: African bonytongue, Heterotis

French name: Poissons sans nom, Heterotis

© www.arowana.de Aquaculture: commercial

Fishery: commercial

Ornemental: commercial Max. size: 100 cm SL Max. weight: 10.2 kg Biology: Pelagic. Its auxiliary branchial air breathing organs enable it to survive in deoxygenated waters. It feeds mostly on plankton. During breeding, it creates a circular nest in swamps. The young leave the nest after a few days and are guarded by the male.

Distribution: In the case of this species, a distinction must be made between the present area of occurrence resulting from man-made introductions, and its original, natural geographical distribution area. It is generally accepted that the first introductions were made in the early fifties of this century. Original (natural) distribution: all water-basins of the Nilo-Sudanese region: rivers Corubal, Senegal, Gambia, Volta, Niger (as well as Benue), Chad, Nile, Omo and lake Turkana. Areas of successful introduction: artificial reservoirs of Côte d’Ivoire (Bandama and Bia basins), rivers Cross, Sanaga, Nyong, Ogowe, Lower and Middle Congo (the species was apparently unable to overcome the Kisangani falls), Ubangui and Kasaï. Attempts to implant the species in Madagascar have generally been fruitless, although it may occur in certain river basins along the eastern coast of the island.

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