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Fish and Shellfish Culture
Fish and shellfish culture is the cultivation of various species of fish and shellfish to increase the yield of useful products, especially food. It is a part of the wider practice of aquaculture, which is the husbandry of aquatic animals and plants.
The vast majority of aquacultural products are food, particularly animal protein, such as fish, mollusks, and crustaceans, but some marine algae and cultured pearls are also raised. Floating algae that form plant or phytoplankton and microscopic animals of the zooplankton are also cultured but on a limited basis only to provide food for confined reared animals, such as shrimps, oysters, and some fishes.
Aquatic husbandry activities include selective breeding, care of the young, feeding, sanitation, environmental modifications, and harvesting. Even though harvesting is relatively easy, since the cultured organisms are, or can be, concentrated in a certain area, the various other activities pose particular problems when performed in water. For this reason most aquaculture is practiced in fresh and brackish water ponds, enclosures, raceways, and reservoirs where the environment can be controlled. The open seas, less amenable to the necessary controls, are not used extensively in aquaculture.
Only species having characteristics that make them suitable and practical for culturing are selected for extensive cultivation. The taste and appeal of the species as a human food is, of course, an important consideration. Since the cultivation of fish and shellfish is expensive and requires extensive labor, most aquacultural products are expensive luxury items such as trout, oysters, and shrimp. However, some lower-priced species, such as carp, are commercially cultured in eastern Europe, China, India, and southeast Asia.
History and Relationship to Agriculture and Fisheries
Aquaculture has ancient origins. A Chinese manual of the 5th century B.C. describes early fish culture practices, and temple friezes dating from the Middle Kingdom (2052–1786 B.C.) of Egypt depict what may have been even earlier attempts at intensive fish rearing. Oysters are known to have been cultivated since at least Roman times.
Aquaculture is related to the raising of domesticated land animals. In both endeavors, control is exercised over various phases of the life cycle of the cultured species. In aquaculture, however, the control is seldom as complete as in the raising of land animals. Aquaculture is also related to fisheries in that the same organisms are produced by both endeavors; fishermen, however, own only the tools of capture, while in aquaculture, the stock as well as the production machinery is owned or leased.
Importance and Potential
Aquaculture is becoming increasingly important as the world's population increases and the problem of food shortages presents itself. Since aquacultural practices produce mainly animal proteins and since this is the nutritional staple in shortest supply in developing countries, considerable hope is being placed on aquaculture as a means of alleviating food shortages.
Although aquaculture is presently practiced in many tropical regions, yields are generally far from optimal, mainly due to lack of capital, inefficient organization, and outdated methods. There are also many areas—such as vast coastal swamps in tropical regions, where animal flesh is scarce—that could be used for aquaculture after some basic, and much applied, research. Another factor limiting production is that only a few aquatic species are at present completely domesticated, and in most cultured species man exercises control over some, but not all, phases of the life cycle. Technical advances arising from current experimentation promise to open up new areas suitable for aquaculture, as well as to make possible the domestication of increasing numbers of aquatic animals and the raising of some in the semidomesticated state.
Indications are that the world's aquacultural production can be increased greatly, provided presently known skills are disseminated rapidly and both basic and adaptive research are continued and expanded. Estimates based on annual yields per unit surface and outputs per man-year of labor indicate that by the year 2000 at least 30 million metric tons could be produced yearly.