Fish Farming( Tercer Parcial)

Fish farming By Romina Flores Rendon

In partial fulfillment for the required for English Class Prof. Rosario Chavez May 3, 2006

The fish Farming Fish farming is the principal form of aquaculture, while other methods may fall under mari culture. It involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally refered to as a fish hatchery. Fish species raised by fish farms include salmon, catfish, tilapia, cod and others. Fish farming, or “aquaculture,” has become a billion-dollar industry, and more than 30 percent of all the sea animals consumed each year are now raised on these “farms. with many land-based aquafarms are indoors, so farmers even control the amount of light that fish get. Basically, there are two kinds of aquaculture: extensive aquaculture based on local photosynthetical production and intensive aquaculture, in which the fishes are fed with external food supply, the management of these two kinds of aquacultural systems is completely different the extensive aquaculture and intensive aquaculture. *Extensive aquaculture: Limiting for fish growth here is the available food supply by natural sources, commonly zooplankton feeding on pelagic algae or benthic animals, such as certain crustaceans and mollusks. Tilapia species filter feed directly on phytoplankton, which makes higher production possible. The photosynthetical production can be increased by fertilizing the pond water with artificial fertilizer mixtures, such as potash, phosphorus, nitrogen and micro elements. Because most fishes are carnivorous, A second point of concern is the risk of algal blooms. When temperatures, nutrient supply and available sunlight are optimal for algal growth, algae multiply their biomass at an exponential rate, eventually leading to an exhaustion of available nutrients. *Intensive aquaculture: In this kind of systems fish production per unit of surface can be increased at will, as long as sufficient oxygen, fresh water and food are provided. Because of the requirement of sufficient fresh water, a massive water purification system must be integrated in the fish farm. A clever way to achieve this is the combination of hydroponics horticulture and water treatment, see below. The exceptions to this rule are cages which are placed in a river or sea, which supplements the fish crop with sufficient fresh water. Especially when fish densities are high, the risk of infections by parasites like fish lice, fungi, intestinal worms, bacteria, and protozoa is much higher than in animal husbandry because of the ease in which pathogens can invade the fish body. This means, intensive aquaculture requires tight monitoring and a high level of expertise of the fish farmer. Proponents of fish farms also suggest that farming salmon reduces fishing pressure on existent wild stocks, and so allows ecosystems to replenish themselves over time. Countering this argument, fish farming opponents point out that the BC and Alaska wild salmon commercial fishery is controlled by wild stock assessment (regardless of fish farm production) and other safe forms of aquaculture like Tilapia or trout farming can be used as well to supply fish to the market.