Water Quality Management For Catfish Culture

WATER QUALITY MANAGEMENT FOR CATFISH CULTURE Dr. Subhendu Datta Sr. Scientist Kolkata, India

Catfishes are belonging to the Order: Siluriformes. These fishes have burbles, which are important in detecting food. Inter muscular bones absent and body is either naked or covered with long plates. They are hardy in nature and can withstand in derelict water bodies. They are air breathing in nature but not all air-breathing fish are catfish. Example: Neomorphic organs for air breathing purpose Magur, Clarias batrachus (Linnaeus) (respiratory tree) Singhi, Heteropneustes fossilis (Bloch) (air tube) Modification of existing organs (e.g. air bladder) for air breathing purpose Wallago, Wallago attu (Schneider) Pabda, Ompok pabo (Hamilton) and Ompok bimaculatus (Bloch) Pangas, Pangasius pangasius (Hamilton) and Pangasius sutchi (Fowler) Seenghala, Aorichthys seenghala (Sykes) Aar, Aorichthys aor (Hamilton) Among these, Magur and Singhi are very important from cultural point of view. Pabda, Pangas and Seenghala are also in the line.

Water management for magur spawn and fry under culture condition: Spawn being small and delicate require good aquatic environment for survival. Therefore, the quality and depth of water in indoor rearing system play a major role for better survivality. Keeping high survivality into account, water management is an important aspect during larval rearing. Aerial respiration commences after 10-11 days. Hence, oxygen must be provided by aerator to larval rearing tank. The dissolved O2 should not be below 5 mg/L. Accumulation of metabolites and unused feeds are common in rearing containers. If remain for long time, these may pollute the environment, which ultimately cause oxygen depletion or disease incidence and mortality. Therefore, it is wise to replenish 7080% of water daily and refill it to maintain 10-15 cm water depth. The water must be clean and free from chlorine. The decomposed and dead fry should be removed periodically to keep the water clean. 1

Once the aerial respiratory habit commences, the tiny fry take vertical trips to surface for atmospheric oxygen. It can be well observed by keeping some fry in beaker. During this time, the water height should be reduced to 8-10 cm to minimize the strain of the fry to travel the long height for gulping the atmospheric oxygen, which ultimately increase the survivality and when they fail to do so, it results in heavy mortality. Gradually water column can be increased as the fry grow up. The spawn can be reared in small round or rectangular shallow plastic containers @ 10,000/sq.m. for about a week. The density can be reduced to half every week to avoid over crowding resulting in quicker growth. Following the above technique, the spawn should be reared for 12-14 days in the indoor containers at a final density of 2000-4000 /sq. m. The excreta of fry and decaying food under high density rearing produce free ammonia (NH3), ionized ammonia (NH4+) and hydrogen sulphide (H2S). Among these, free ammonia is toxic at low concentration, affecting the gills and accessory respiratory organs where as hydrogen sulphide causes stress to the fry. Due to the high density of fry rearing, there may be increase in carbon dioxide because of respiratory cycle, resulting in stress. In Clarias spp., CO2, NH3 and NH4 concentration level up to 15 ppm, 0.05 ppm and 0.25 ppm respectively may not affect larvae but it could be dangerous if the level continues for a longer time. So vigorous aeration and frequent water exchange is required to get rid of the above problem.

Water management for grow-out catfishes: 1. Selection of Water area: Catfishes may be cultured in any sort of water body whether large or small. However, for proper and easier management, the area should not be more than 1 ha – 2 ha. Magur culture should be undertaken in small (0.01-0.1 ha), shallow (0.75- 1.0 m water depth) ponds with not more than 15 cm of mud at the bottom for better growth and easy harvesting. 2. Some features of catfishes important for water quality management point of view: (a). Development of accessory respiratory organs, which helps in aerial respiration. Therefore, culture of catfish is possible in water, which are generally quite deficient in dissolved oxygen content 2

(b). They are having high quantity and high quality of haemoglobin in RBC so that more amount of oxygen can be absorbed. (c). They can tolerate high concentrations of carbon dioxide (up to 100 ppm) in blood so can withstand in acidic pH but not below 5 (free CO2 dominates in water having pH 5 – 6.5). Above three points makes catfishes quite hardy and therefore, can be cultured under extensive culture system in swamps, marshes, wetlands, oxidation ponds and other derelict water bodies where carp culture is not possible. 3. Depth of water: In their natural habitat, catfishes have to take recourse to direct aerial respiration by moving up to gulp the air to the air-water inter phase at the pond surface periodically. Energy require for catfish for this vertical upward movement very much restrict the time for food procurement and hence prefer energy rich carnivorous diet (Pandian, 1979). Therefore, depth of water bodies should not be very high (0.75 – 1.0 m). However, depth should not be less than 2 ft in summer. Traditional nursery and rearing ponds of carp culture can be utilized during the off-season (January to June) for culture of catfishes. 6. Water exchange: Many of the problems of poor water quality, diseases and mortality in catfish ponds are due to the heavy rates of feeding. Water in many ponds gives the appearance of a pea soup with quantities of uneaten feed and blooms of algae. The fishes are voracious food in takers. Thus, increased excretion of excreta causes accumulation of NH3-N. Feeding with more than 0.5 Kg feed/m2 has been found to result in water pollution and fish mortality, in spite of hardy nature of catfish and their ability to breathe atmospheric air. Frequent water exchange, when possible is efficient means of pond sanitation and maintenance of water quality standards (Pillay, 1995). At Kalyani, West Bengal, the water of the pond was changed only once a month from an adjacent irrigation canal or partially changed at an interval of 10 days from a deep tube well during intensive culture of magur (Dehadrai, 1978). Intensive culture of magur was also done in recirculatory-filtering ponds at CICFRI, Barrackpore, with rate of feeding 4-6% of body weight and water circulation was effective for 4 hours per day (Jhingran, 1991). In Thailand, when fingerlings are first stocked, the pond is only filled to a depth of 50 to 80 cm. After about 3 week, the water level is increased to 1.0 to 1.5m. After the 7th or 8th week, there is a 3-4 hour daily partial water change. However, if the water becomes too turbid (turning to black in colour), the entire 3

pond is drained and refilled. More frequent water changes are preferred, if possible. 7. Presence of aquatic weed: Presence of naturally occurring aquatic weed e.g. Eichhornia or Lemna in catfish culture ponds not only provide protection against poachers, but also controls algal bloom (pl. see point 8), provide shade, shelter and encourage the growth of aquatic insects, which are consumed by the fish. Therefore, provide a few patches of aquatic plants along the margin of pond. See that the plants don’t occupy more than 1/4th of the pond area, this is because if the surface water is fully covered by floating weeds that may create hindrance to air-breathing activity of catfishes. 8. Control of algal bloom: Occasionally there may be excessive accumulation of metabolites, rise in ammonia content or occurrence of algal bloom in the pond, if feeding is not controlled. Treatment of water with potassium permanganate at the rate of 300 ppm in such cases helps. Spreading of Lamna or water hyacinth in the pond controls algal blooms. Under acute conditions of fouling, a change of pond water is recommended (pl. see point 6). Use of weedicides may be avoided when fish stock is growing in the pond. If the foul water were to be changed, it would be gainfully used in the neighbouring agricultural fields for irrigation and fertilization. 9. H2S poisoning: Accumulation of hydrogen sulphide (H2S) is another cause of mortality in catfish culture ponds. Remedy: water exchange. 10. Salinity: Magur, Singhi though thrive well in swamp and weedy marshes, can also withstand slightly brackish waters. 11. Feeding strategies for low water pollution under intensive culture: For maximum growth generally fish are fed at a high rate. However, it is difficult to recover the uneaten feed. Overfeeding represents not only an economic waste, but also greater oxygen demand on the culture system. In large ponds, feed is dispensed from all sides; so all the fish would get the feeding opportunity. Feeding along the down wind side of the pond should be avoided. Catfish should be fed at least twice daily. The farmer must evaluate the benefits of faster weight gain in light of the additional cost of more frequent feeding. Optimum time of day for feeding catfish in pond is influenced by dissolved oxygen and water temperature. Low dissolved oxygen depresses feeding activity of catfish. A good quality of water with rich oxygen content is required for magur for faster growth in spite of its air-breathing organ. Another 4

main important consideration for feeding is the food for fish should have high degree of water stability. Either extruded or pelleted feed must be offered to reduce leaching of the nutrient, hence dust or dough form of feed is discouraged in catfish culture for low water pollution. The rate of feeding should not be more than 6-8% of the body weight.

Suggested readings: 1.Chaudhuri, H. (1971). Culture of air-breathing fishes. First Workshop on All India Coordinated Research Project on Air-breathing Fishes, Cuttack-1, Orissa. pp.6. 2. Dehadrai, P. V. (1975). Derelict waters for air breathing fish culture. Indian Farming. 25 (6): 19-20. 3. Dehadrai, P. V. and Thakur, N. K. (1980). Magur and Singhi fish culture. Extension Pamphlet, CICFRI, Barrackpore, West Bengal, pp.6. 4. Ramaswami, L.S. and Sunderaraj, B. I. (1955). Induced spawning in the Indian catfish. Science. 123: 1080. 5. Rao, G. R., Tripathi, S. D. and Sahu, A. K. (1994). Breeding and seed production of the Asian Catfish, Clarias batrachus. Manual Series (3): CIFA. Bhubaneswar. 48 pp.

References: 1. Coleman J. A. (1982). Pond Management, Water Envioronment and Fish Growout Performances Relationships in Clarias culture Trials. National Inland Fisheries Institute, Bangkok. 2. Dehadrai, P.V. (1978). Fourth Workshop Report of All India Coordinated Research Project on Air-breathing fish culture at CICFRI, Barrackpore. Dec. 1213,1978. 3. Pandian, T. J. (1979). Experimental studies on the scope for enhancing productivity of air breathing fishes. In: Symposiu on Inland aquaculture (Abstract), February 12-14, 1979: 112, CICFRI, Barrackpore. 4. Pillay, T. V. (1995). Chapter 17. Catfishes. In Aquaculture Principle and Practices. P. 333- 350. Fishing News Books, Osney Mead, Oxford OX2 OEL, England.

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