Mariculture

Mariculture is the cultivation and harvest of marine flora and fauna in a controlled saltwater environment . Sometimes called marine fish farming, marine aquaculture , or aquatic farming, mariculture involves some degree of human intervention to enhance the quality and/or quantity of a marine harvest. This may be achieved by feeding practices, protection from predators, breeding programs, or other means.

Fish, crustaceans, salt-water plants, and shellfish may be farm raised for bait, fishmeal and fish oil production, scientific research, biotechnology development, and repopulating threatened or endangered species . Ornamental fish are also sometimes raised by fish farms for commercial sales. The most widespread use of aquaculture, however, is the production of marine life for human food consumption. With seafood consumption steadily rising and overfishing of the seas a growing global problem, mariculture has been hailed as a low-cost, high-yield source of animal-derived protein.

According to the Fisheries Department of the United Nations' Food and Agriculture Organization (FAO), over 33 million metric tons of fish and shellfish encompassing 220 different species are cultured (or farmed) worldwide, representing an estimated $49 billion in 1999. Pound for pound, China leads the world in aquaculture production with 32.5% of world output. In comparison, the United States is only responsible for 4.4% of global aquaculture output by weight. Just 7% of the total U.S. aquatic production (both farmed and captured resources) is attributable to aquaculture (compared to 62% of China's total aquatic output).

In the United States, Atlantic salmon and channel catfish represent the largest segments of aquaculture production (34% and 40%, respectively, in 1997). Though most farmed seafood is consumed domestically, the United States imports over half of its total edible seafood annually, representing a $7 billion annual trade deficit in 2001. The Department of Commerce launched an aquaculture expansion program in 1999 with the goal of increasing domestic seafood supply derived from aquaculture production to $5 billion annually by the year 2025. According to the U.S. Joint Subcommittee on Aquaculture, U.S. aquaculture interests harvested 842 million pounds of product at an estimated value of $987 million in 1999.

To encourage further growth of the U.S. aquaculture industry, the National Aquaculture Act was passed in 1980 (with amendments in 1985 and 1996). The Act established funding and mandated the development of a national aquaculture plan that would encourage "aquaculture activities and programs in both the public and private sectors of the economy; that will result in increased aquacultural production, the coordination of domestic aquaculture efforts, the conservation and enhancement of aquatic resources, the creation of new industries and job opportunities, and other national benefits."

In the United States, aquaculture is regulated by the U.S. Department of Agriculture (USDA) and the Department of Commerce through the National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA). State and local authorities may also have some input into the location and practices of mariculture facilities if they are located within an area governed by a Coastal Zone Management Plan (CZMP). Coastal Zone Management Plans, as authorized by the Coastal Zone Management Act (CZMA) of 1972, allow individual states to determine the appropriate use and development of their respective coastal zones. Subsequent amendments to the CZMA have also made provision for states to be eligible for federal funding for the creation of state plans, procedures, and regulations for mariculture activities in the coastal zone.

Tilapia, catfish, striped bass, yellow perch, walleye, salmon, and trout are just a few of the fresh and salt-water finned fish species farmed in the United States. Crawfish, shrimp, and shellfish are also cultured in the U.S. Some shellfish, such as oysters, mussels, and clams, are "planted" as juveniles and farmed to maturity, when they are harvested and sold. Shellfish farmers buy the juvenile shellfish (known as "spat") from shellfish hatcheries and nurseries. Oysters and mussels are attached to lines or nets and put in a controlled ocean environment, while clams are buried in the beach or in sandy substrate below low tide. All three of these shellfish species feed on plankton from salt water.

But just as overfarming takes a toll on terrestrial natural resources , aquaculture without appropriate environmental management can damage native ecosystems. Farmed fish are raised in open-flow pens and nets. Because large populations of farmed fish are often raised in confined areas, disease spreads easily and rapidly among them. And farmed fish often transmit sea lice and other parasites and diseases to wild fish, wiping out or crippling native stock. Organic pollution from effluent , the waste products from farmed fish, can build up and suffocate marine life on the sea floor below farming pens. This waste includes fish feces, which contributes to nutrient loading , and chemicals and drugs used to keep the fish disease free and promote growth. It also contains excess fish food, which often contains dyes to make farmed fish flesh more aesthetically analogous to its wild counterparts.

Farmed fish that escape from their pens interbreed with wild fish and weaken the genetic line of the native stock. If escaped fish are diseased, they can trigger outbreaks among indigenous marine life. Infectious Salmon Anemia , a viral disease that has plagued fish farms in New Brunswick and Scotland in the 1990s, was eventually found in native salmon. In 2001, the disease first appeared at U.S. Atlantic salmon farms off the coast of Maine.

The use of drugs in farmed fish and shellfish intended for human consumption is regulated by the U.S. Food and Drug Administration (FDA). In recent years, antibiotic resistance has been a growing issue in aquaculture, as fish have been treated with a wide array of human and veterinary antibiotic drugs to prevent disease.

The commercial development of genetically-engineered, or transgenic, farmed fish is also regulated by FDA. As of May 2002, no transgenic fish had been cleared by FDA for human consumption. The impact transgenic fish may have on the survival and reproduction of native species will have to be closely followed if and when commercial farming begins.

As mandated by the 1938 Mitchell Act, the NMFS funds 25 salmon hatcheries in the Columbia River Basin of the Pacific Northwest, the largest federal marine fishery program in the United States. These aquaculture facilities were originally introduced to assist in repopulation of salmon stocks that had been lost to or severely hampered by hydroelectric dam projects. However, some environmentalists charge that the salmon hatcheries may actually be endangering wild salmon further, by competing for local habitat and weakening the genetic line of native species.

Without careful resource management, aquaculture may eventually take an irreversible toll on other non-farmed marine species. Small pelagic fish, such as herring, anchovy, and chub, are captured and processed into fish food compounds for high-density carnivorous fish farms. According to the FAO, at its current rate, fish farming is consuming twice as many wild fish in feeding their domestic counterparts as aquaculture is producing in fish harvests—an average of 1.9 kg of wild fish required for every kilogram of fish farmed.

No matter how economically sound mariculture has been, it has also led to serious habitat modification and destruction, especially in mangrove forests. In the past twenty years, the area of mangrove forests have dwindled by 35% worldwide. Though some of that loss is due to active herbicide control of mangroves, their conversion to salt flats, and the industrial harvesting of forest products (wood chips and lumber), mariculture is responsible for 52% of the world's mangrove losses.

Mangrove forests are important to the environment because these ecosystems are buffer zones between saltwater areas and freshwater/land areas. Mangroves act as filters for agricultural nutrients and pollutants, trapping these contaminants before they reach the deeper waters of the ocean. They also prevent coastal erosion , provide spawning and nursery areas for fish and shellfish, host a variety of migratory wildlife (birds, fish, and mammals), and support habitats for a number of endangered species.

Shrimp farming, in particular, has played a major role in mangrove forest reduction. Increasing from 3% to 30% in less than 15 years, commercial shrimp farming has impacted coastal mangroves profoundly by cutting down mangrove trees to create shrimp and prawn ponds. In the Philippines, 50% of the mangrove environments were converted to ponds and between 50% and 80% of those in Southeast Asia were lost to pond culture as well.

Shrimp mariculture places high demands on resources. It requires large supplies of juvenile shrimp, which can seriously deplete natural shrimp stocks, and large quantities of shrimp meal to feed them. There also is considerable waste derived from shrimp production. This can pump organic matter and nutrients into the ponds, causing eutrophication, which causes algae bloom and oxygen depletion in the ponds themselves or even downstream. Many shrimp farmers need to pump pesticides, fungicides, parasiticides, and algicides into the ponds between harvests to sterilize them and mitigate the effects of nutrient loading. Shrimp ponds also have extremely short life spans, usually about 5–10 years, forcing their abandonment and the cutting of more mangrove forests to create new ponds.

Mariculture also limits other marine activities along coastal waters. Some aquaculture facilities can occupy large expanses of ocean along beaches which become commercial and recreational no-fish zones. These nursery areas are also sensitive to disturbances by recreational activities like boating or swimming and the introduction of pathogens by domestic or farm animals.

[Paula Anne Ford-Martin ]

RESOURCES

BOOKS

Food and Agriculture Organization of the United Nations. The State of World Fisheries and Aquaculture Rome, Italy: FAO, 2000. [cited June 5, 2002]. <http://www.fao.org/DOCREP/003/X8002E/X8002E00.htm>.

Jahncke, Michael L. et al.Public, Animal, and Environmental Aquaculture Health Issues. New York: John Wiley & Sons, 2002.

Olin, Paul. "Current Status of Aquaculture in North America." From Aquaculture in the Third Millennium: Technical Proceedings of the Conference on Aquaculture in the Third Millennium, Bangkok, Thailand. 20-25 February 2000. Rome, Italy: FAO, 2000.

PERIODICALS

Barcott, Bruce, and Natalie Fobes. "Aquaculture's Troubled Harvest." Mother Jones 26, no.6 (November –December 2001): 38 (8).

Naylor, Rosamond, et al. "Effect of Aquaculture on World Fish Supplies."-Nature (June 29, 2000).

OTHER

"National Aquaculture Policy, Planning, and Development." 16 USC 2801. [cited June 4, 2002]. <http://www.access.gpo.gov/uscode/title16/chapter48_.html>.

National Marine Fisheries Service, National Oceanic and Atmospheric Administration. Aquaculture. [cited July 2002]. <http://www.nmfs.noaa.gov/aquaculture.htm>.

ORGANIZATIONS

The Northeast Regional Aquaculture Center, University of Massachusetts Dartmouth, Violette Building, Room 201 285 Old Westport Road, Dartmouth, MA USA 02747-2300 (508) 999-8157, Fax: (508) 999-8590, Toll Free: (866) 472-NRAC (6722), Email: [email protected], http://www.umassd.edu/specialprograms/NRAC/