Aquaculture is the human-controlled cultivation and harvest of freshwater and marine plants and animals. Synonyms include fish farming, fish culture, mariculture, fish breeding and ocean ranching. Throughout the world, aquaculture operations constitute an integral part of fisheries and aquatic resource management. Organisms as varied as trout, carp and tuna (ie, finfish), shrimps and oysters (ie, shellfish) and seaweed are grown, using ponds, tanks or nets, in salt, brackish and fresh waters.

Worldwide Aquaculture Production

In 1992 total worldwide aquaculture production amounted to about 19.3 million t. That is roughly 19% of the total world fish production compared to 10% a decade earlier. Aquaculture production is growing extremely rapidly. From 1971-80, there was a 73% increase in total production, and this was followed by another 90% increase in the 10 years prior to 1992. FAO (United Nations Food and Agricultural Organization) projections are for a further 40% increase by the year 2000 and a doubling of that production by 2025. Of aquaculture production, 48.8% was finfish (eg, carp, salmon); 18.1% molluscs (eg, oysters, mussels); 27.9% seaweeds (eg, kelp); and about 5.1% crustaceans (eg, lobsters, shrimp). Carp (6.7 million t in 1992), tilapia (474 000 t), salmon and trout (629 000 t), shrimp (884 000 t), oysters (954 000 t) and mussels (1.1 million t) are the major cash crops worldwide.

Almost every country has some form of aquaculture. The world's major producers are in Southeast Asia, with 80% of the total, China, India and Japan, Korea, Philippines, Indonesia and Thailand being the leaders in the region. Traditionally, the emphasis has been on species that find wide acceptance among all social groups; eg, trout and salmon in North America and northern Europe, carp in eastern Europe and Israel, mussels in France and Spain, prawns and milkfish in the Philippines, Asian species of carp in Southeast Asia, and seaweeds in Japan and Korea. More recently in both traditional and new areas such as Latin America and Australia, there has been increasing emphasis on luxury products; eg, freshwater prawns, marine shrimp and salmon for specific markets or export, and the total production of such items is growing rapidly.

Origins of Aquaculture

The origins of aquaculture go back thousands of years. Oysters in Japan and fish in Egypt were cultured before 2000 BC. In China, domestication of carp, the most commonly cultured fish, began 5 centuries earlier than in Europe. The first book on fish culture was reportedly written by a Chinese scholar, Fan Li, in the 5th century BC. Carp were introduced to Europe from the Danube River by the Romans in the 1st to 4th centuries AD. Culture techniques were refined by monks during the 14th to 16th centuries. Trout were first raised in a hatchery in Germany in 1741, and the first attempts at commercial trout culture were made as early as 1853 in the US. Rainbow trout, once found only in North America, are now cultured throughout the world. Shrimp and other species of fish once considered almost impossible to grow successfully in captivity are now cultured in many tropical and subtropical regions and many other species are presently being examined for future culture potential.

Aquaculture Technologies

Aquaculture practices may be categorized by the degree of human control over production. The following arrangement is in order of increasing control.

Release of Young into the Wild
A well-known practice, the stocking of lakes and streams with young trout, is commonly used by federal and provincial hatcheries, and involves rearing the fish in a hatchery from a few weeks to over a year. Once stocked, the fish are exposed to all the hazards of nature, such as predatory fish and birds.

Raft Culture of Molluscs and Seaweed
In this type of culture, ropes or nets are suspended from floating rafts. The animals or plants such as mussels, skills or kelp become attached to the ropes or nets and obtain food and nutrients from the water. The organisms are not fed, but they are protected from bottom-dwelling predators and are not as subject to crowding as they would be in nature.

Cage Culture of Finfish
Significant advantages can be obtained by growing fish in floating cages. For example, Atlantic salmon are confined in large (20m x 20m), nylon-mesh cages. The cages, held in specially chosen areas of a protected coastline, are supplied daily with specially prepared foods. Safe from birds and other fish, the salmon grow rapidly and most survive to a marketable size.

Pond Culture of Fish
By growing fish in man-made earthen or concrete ponds, even greater control can be maintained. Trout, carp, catfish and numerous other species are supplied with food - either prepared diets or natural food produced by fertilizing the pond waters. The fishes' environment can be improved by adding or aerating water, or treating it with chemicals.

Intensive Tank Culture
In the most intensive systems as many aspects of the environment are controlled as is technically possible. Fish are grown in concrete or plastic tanks or troughs. Pumps supply a constant flow of water at controlled temperatures. Custom-prepared food is given at specified times from automatic feeders. Specially bred disease-free stocks of fish are used to provide a regular flow of uniform product for markets.

Canadian Aquaculture

The originator of Canadian aquaculture was Samuel Wilmot, who developed techniques for salmon and trout in the 1860s and 1870s that were so successful that nearly a century elapsed before significant changes were made in Canadian trout hatcheries. Most early Canadian aquaculture operations were operated by governments and involved, almost exclusively, the hatching and rearing of young fish in hatcheries for release in the wild for commercial and sport fisheries.

Starting in the 1960s the value of nongovernment production rose, and it is now much higher than government production. Some private or commercial aquaculture production is for private sportfishing, but the majority is for direct sale as food in local and export markets. In 1994 Canadian aquaculturists produced 54 500 t of finfish and shellfish valued at $297 million, approximately 10% of the value of the total Canadian commercial ocean fisheries. Major species produced are salmon, oysters, mussels, clams, trout and Arctic char.

British Columbia

The types of aquaculture operations in Canada vary considerably from region to region. On the West Coast throughout the 1970s and 1980s, there was a large increase in the rearing and stocking of Pacific salmon, as part of the Canada-BC Salmonid Enhancement Program. The goal of this program was to double commercial and sport harvest of salmon. Private cage culture operations for growing salmon for market have also been established and the numbers have expanded greatly - to close to 100 by 1994. The total value of cultured salmon and trout produced is now approaching $150 million. BC is also a significant producer of cultured Pacific oysters and clams, and scallop culture is also growing.

Canadian Inland Waters

Production in inland waters in Canada is much smaller than ocean culture, with a total value of $27 million. On the Prairies, many grain and cattle farmers regularly stock small prairie pothole lakes with rainbow trout fingerlings in spring and harvest pan-size fish in fall. The production is mainly for private use, but increasing numbers are being marketed commercially. Cage rearing of trout is also being attempted and there are small-scale projects growing Arctic char in tanks. Significant numbers of walleye and whitefish fry are stocked from government hatcheries into large lakes in attempts to enhance and rehabilitate important commercial fisheries.

In Ontario and Québec, rainbow and brook trout are reared in ponds and tanks, and recently cage rearing has been attempted. The major production of fish, for direct sale to stores and restaurants, is in these 2 provinces, but there is also significant production of trout for stocking of private fishing ponds. The Ontario government has been stocking Pacific salmon and lake trout in the great lakes in order to rehabilitate the fisheries there.

Atlantic Provinces

In the Atlantic provinces, the federal government has been stocking hatchery-reared Atlantic salmon and trout since the 1880s. Recently, cage culture of Atlantic salmon and rainbow trout has been established in the Bras d'Or Lake and the south coasts of Nova Scotia and primarily New Brunswick. Production of Atlantic salmon in cages rose from 78 t in 1981 to 297 t in 1986 and to 12 400 t in 1994. Another East Coast success has been the culture of blue mussels, primarily in Prince Edward Island. In 1981 there was virtually no culture of mussels. By 1986, production rose to 1777 t valued at over $2.7 million and by 1994 it had reached 6898 t valued at over $6.6 million.

The Future

In the mid-1980s federal and provincial governments in Canada began actions to clarify legislation and regulations related to aquaculture and to co-ordinate government and industry action leading to aquaculture developments. In 1995 a long-awaited federal aquaculture strategy was released. The success of aquaculture operations in Canada will depend on new knowledge from government, university and industry scientists, the availability of land, water and capital, on technologies employed, market acceptance, and the technical and business competence of the entrepreneur. Based on the past 2 decades the future is very promising.