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Aquaculture

by Mike Rice
P1415

aquaculture.gif (5971 bytes)Aquaculture is a form of agriculture in which aquatic plants and animals are reared in artificial or semi-natural conditions.

There are many forms of aquaculture. Typically, most people think of aquaculture as the cultivation of fish and shellfish for seafood markets and human consumption, but the scope of aquaculture is much broader.

In some parts of the world, seaweeds are cultured for human food and for important food additives, such as agar and carrageenan, that are sold worldwide.

Aquaculture of fish and aquatic plants for the aquarium trade or for water gardens is an important business in this country, as is the aquaculture of bait fish to supply an ever-growing sportfish industry.

Aquaculture is also carried out to supply markets for shells and shell products. Most pearls, both freshwater and saltwater, have aquaculture origins.

Additionally, some semi-aquatic plants, such as cranberries, might be considered to be produced through aquacultural methods.

In the last 30 years, there have been methods developed for the cultivation of terrestrial plants, such as lettuce and tomato, whereby no soil is used and their roots are suspended into nutrient-laden water. This practice is called hydroponics; but, strictly speaking, this is not aquaculture because the plants are not normally considered aquatic or semi-aquatic.

Aquaculture systems have been developed in which water containing wastes from aquacultured fish is used to culture hydroponic vegetables. This ingenious use of aquaculture waste resources is a form of integrated culture (aquaculture in concert with terrestrial aquaculture).

In other parts of the world, there are a number of very successful commercial applications of integrated culture. In much of Southeast Asia, a hardy African fish, called tilapia, is cultured along with rice in flooded fields. In China, it is common to fertilize fish ponds with wastes from farm animals, such as chickens or swine. In the bayou country of Louisiana, the integrated culture of crayfish and rice is common practice.

The scope and intensity of aquaculture can vary greatly depending upon the species cultured, financial resources of the aquaculturist, the degree of management required, and the amount of risk that the aquaculturist wishes to assume. For example, some aquaculture schemes can cover an extensive area with very little management involved.

An example of extensive aquaculture might be the bottom culture of oysters using the traditional methods practiced in Narragansett Bay during the late 19th and early 20th centuries. Large areas of Narragansett Bay were leased to a number of oyster companies, who laid down old oyster shells as cultch or setting material for juvenile oysters.

Alternatively, seed oysters were brought in from outside seed beds. Efforts were taken to remove oyster predators like sea stars, but the overall management of these beds was not very complicated. After approximately two years, oysters would be harvested by dredging and sold wholesale to markets in New York or Boston.

Extensive aquaculture systems still operate with great economic benefit. As of 1992, Connecticut was one of the largest oyster-producing states in the country with harvests amounting from $50 to $60 million. There, extensive techniques of farming Long Island Sound are still used, much as the old-timers did in the early part of the 20th century. Many other uses of the waterway, such as recreational boating and fishing, occur simultaneously—with minimal conflicts due to appropriate governmental management of the public waters.

Aquaculture can also use very intensive systems, which require a high degree of management skill and fairly high input of capital investment. Intensive systems rely on very high stocking densities of aquatic livestock, so the emphasis is on a high degree of water quality management for encouraging growth, reducing stress, and controlling disease. High quality nutritious feeds are required.

In most intensive aquaculture systems, fish or other aquatic organisms are on total life support. Examples of intensive aquaculture systems include indoor culture of hybrid striped bass or summer flounder in recirculating tanks.

In very intense aquaculture systems, fish may be stocked at densities as high as one or two pounds of fish per gallon of water in the tanks. Backup systems for intensive systems of this type might include backup generators to keep water circulating during power failures or compressed oxygen gas for emergency aeration.

Much like terrestrial animal husbandry, aquaculturists are concerned with a number of factors that affect the growth and marketability of their livestock. As a business, aquafarmers also need to be concerned with producing high quality products with minimal cost. Knowledge of specific nutritional requirements and improvement in feed quality can lead to greater production and profitability.

As aquaculture methods advance, it is likely that aquaculture will grow in importance as a source of high quality seafood products. Consumer demand for seafood keeps growing, and the world's capture fisheries are reaching their maximum harvest potential. With declining catches in coastal fisheries in New England, the choice is to develop aquaculture as a local supply of seafood—or to rely upon increased imports from abroad.

In many countries in Europe and Asia, aquaculture has become a well-developed industry largely because their coastal capture fisheries were overfished decades before our North American fisheries. The aquaculture industries in Europe and Asia are large enough to not only support their own domestic seafood markets, but to supply valuable export markets as well.

For further reading:

Huner, J.V. and E.E. Brown. 1985. Crustacean and Mollusk Aquaculture in the United States. AVI/Van Nostrand Reinhold, New York. 476pp.

Rice, M.A. and A.R. Ganz. 1994. Planning an Aquaculture Business in Rhode Island: Getting Started. Rhode Island Sea Grant Publication #RIU-H-94-003, University of Rhode Island, Narragansett. 39pp.

Stickney, R.R. 1994. Principles of Aquaculture. John Wiley, New York. 502pp.

Minnesota Sea Grant  Aquaculture Links

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