Aquaculture has been one of the fastest growing segments of global food production in recent decades, and has been hailed as an answer to the limits of wild fish stock harvest.

Fish and other aquacultured species are generally very efficient converters of feedstuffs into high quality protein when compared to other farmed animals. For example a catfish may take 6 kg of feed (wet weight to wet weight) to produce 1 kg of catfish whereas a chicken might take 10 kg and a pig 30 kg. This is possible primarily because aquaculture species are cold-blooded (or more corectly - poikilothermic), and hence do not waste energy on heating, and because the physics of the aquatic environmment require little energy for movement. Fish and other aquacultured species also tend to be comprised of a higher percentage of edible weight than terrestrial species.

Farming of high value (and often overexploited) species can reduce presure on wild stocks.

There are inumerable aquatic species farmed in small quantities around the world. Major aquaculture industries around the world include (Apology: latin names are from top of head and may be mis-spelled):

Atlantic salmon (Salmo salar) and Rainbow trout (Oncorhynchus mykiss). Also smaller volumes of a variety of other salmonids. Originally developed in Norway, Denmark (Rainbow trout although it is an American species) and Scotland, now farmed in significant quatities in Europe, Canada, Chile and Australia (Tasmania). First or Second in the world for production value.

Tropical shrimp; Mostly Black tiger shrimp (Penaeus monodon) and increasingly White shrimp (Litopenaeus vannemi). Techniques originally developed in Japan and Taiwan. Mostly farmed through tropical and sub-tropical Asia and South America. First or Second in the world for production value.

Carps; European carp, Chinese carps (Grass, Silver and Black) and Indian major carps are easily the largest global aquaculture industry by volume of production but are low in value. Major producers are China, India, Southeat Asia and Europe. China's reported production figures are considered contentious by some authorities. Value of production is also debatable according to whether value is calculated at border (exchange rate) prices or PPP (Purchasing Power Parity) prices. Nonetheless, carps are major contributors of high quality protein to the diets of poorer people around the world.

Seaweeds; Many species. Huge volumes, low value. Mostly farmed in Asia; particuarly Japan, Korea and China. Also farmed in Nova Scotia, Canada.

Catfish; Major species are Vietmanese basa (), Channel catfish and African and Asian walking catfish (Clarias sp.). Mostly farmed in Asia and the Southern United States.

Tilapia; Nile tilapia and a few other species. Very well suited species to subsistance farming although arguably not well suited to large aquabusiness due to finicky breeding biology and low flesh recovery (Although becoming a very successful import in the US and Europe). Mostly farmed in Asia, South America and Africa.

Oysters; Pacific oyster (Crassostrea gigas), American oyster (Crassostrea virginica), Flat oyster (Ostrea edulis), the Sydney rock oyster (Saccostrea glomerata) and others. Mostly farmed in Asia, US, Australia-New Zealand and Europe. Flat oyster was once a huge industry and low cost/very high quality food for the masses in Europe but collapsed under mortalities brought about by the parasite Bonamia.

Mussels; Blue mussel (Mytilus edulis), Green mussels (Perna sp.) Mostly farmed in Europe, Asia, New Zealand and South America.

These industries are often based in developing countries, and can contribute greatly to food security/quality and income there. Of those industries above, all but Tropical shrimp and salmonids have a low level environmental impact. The environmental footprint of the Tropical shrimp and salmonid industries is improving.

Tuna farming in Australia has seen financial success. Tuna farming at present is really a fattening enterprise, where wild bred juvenile tuna are captured and grown in pens to a larger size and better flesh quality. Having the fish confined in pens also means that harvests can be timed to suit the market. This practice has resulted (at least in Australia) on reduced pressure on wild populations and a much larger value for their relatively small wild (Southern bluefin) tuna quota. Relatively recently, researchers in Japan have closed the life cycle of the Pacific bluefin tuna, and European researchers in Spain are working on breeding Northern bluefin tuna.

While the negative impacts of some aquaculture on the environment has been widely publicised, the positive environmental effects of aquaculture are rarely noted. For example many aquacultured species are highly sensitive to water quality conditions and aquaculture farmers often notice the effects of pollution or reductions in water quality before other authorities. Aquaculture businesses have a vested interest in clean waterways, in that a reduction in water quality has a direct effect on their production rates and financial bottom line. Appropriate aquaculture development can serve as 'canaries' for the health of waterways, with farms often a very new and undeveloped industry when compared to terrestrial aquacultures. Only a few species (Atlantic salmon, Pacific white shrimp and possibly several species each of catfish, carp and tilapia) are currently on their way to becoming true domesticated aquabuisiness species in the way that poultry, beef and pork have long been. While the aquaculture industry is still only a small way into the development curve the inherent biological characteristics of aquatic animals bode well for the future contribution of aquatic farming to living standards and the environment.

White Seabass are being raised by sport fishing interests in Southern California for release into the wild to re-stock once depleted natural population. This program is not a commercial enterprise but for the benefit of the anglers who go fishing in the ocean in general. The effectiveness of the program is recorded by an elaborate program of tagging the head of every fish before release and asking anglers and fishermen to return the heads of caught fish for scientific study and recovery of the tags.

Cite: Wikipedia