Blue Revolution (Aquaculture)
Fish farming is a relatively intensive enterprise. It commonly involves the management of all stages in the life cycle of the cultivated fish, from the production of eggs and larvae, through to growth and eventual harvest of high-quality, market-sized fish. In this sense, fish farming is different from fish ranching, which is a less-intensive enterprise that usually involves the confinement and feeding of captured wild fish in order to increase their market value. This is done, for example, with bluefin tuna (Thunnus thynnus) in some places.
Fish have many potential benefits as cultivated species. Because they are cold-blooded (or poikilothermic), fish divert little energy to maintaining their body temperature, and can therefore convert a relatively large proportion of their food into their growing biomass. In other words, populations of fish can be very productive, especially under conditions where the animals are well-fed and the rates of mortality from disease and predation are kept small. Moreover, fish are a tasty and highly nutritious food for humans. Consequently, the economic value of fish is great, as are the potential profits gained from cultivating them in large quantities.
Various species of fish are grown in aquaculture, using a variety of cultivation systems. The systems most commonly involve confinement in artificial ponds, or in cages set into larger bodies of water, including the ocean. The fish are fed with a nutritious diet, sometimes to excess so that their growth rate is maximized. When the fish are economically mature, they are carefully harvested and processed so that the highest-value economic products can be delivered to consumers.
The oldest fish-farming systems were developed in eastern Asia, and involved several species of freshwater fish. The first writings about methods of fish culture are dated from about 2,500 years ago and were written by Fan Lei, a wealthy Chinese fish farmer. The first species to be grown in aquaculture was probably the common carp (Cyprinus carpio), a species native to China but now spread throughout the world. It is still an extremely important species in aquaculture. Other so-called Chinese carps are also important in Asian fish-farming, including the grass carp (Ctenopharyngodon idella), big-head carp (Aristichtys nobilis), and silver carp (Hypophthalmichtys molitrix). Other prominent species are tilapia (Tilapia mossambica and other Tilapia species) and Asian catfish (Clarias spp.).
Freshwater fish are also cultivated in North America and Europe. Most commonly grown are species of trout, especially brook trout (Salvelinus fontinalis) and rainbow trout (Salmo gairdneri). Also important are channel catfish (Ictalurus punctatus) and the common carp.
Fewer species and quantities of fish are grown under brackish-water conditions in Asia, but they include the milkfish (Chanos chanos). Brackish and saltwater fish farming are larger enterprises in northern Europe, North America, and western South America, and New Zealand, where species of trout and salmon are commonly cultivated, sometimes in large, open-water complexes of cages supported by rafts. Especially important species are Atlantic salmon (Salmo salar), brown trout (S. trutta), and Pacific salmon (Oncorhynchus spp.).
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