Global aquaculture production is growing rapidly, with production more than doubling in weight and by value from 1989 to 1998. With many capture fisheries catches peaking, scientists, governments, and international organizations all point to aquaculture as the most important means to increase global fish supplies.
The aquaculture industry in the United States, which is dominated by freshwater catfish (Ictalurus punctatus) production, generates about one billion dollars each year. Marine aquaculture comprises roughly one-third of U.S. production by weight, and despite rapid increases in salmon and clam production, growth of U.S. marine aquaculture has been slow on average. Efforts to develop marine aquaculture in the open ocean could catalyze future growth.
Aquaculture has a number of economic and other benefits. But if it is done without adequate environmental safeguards it can cause environmental degredation. The main environmental effects of marine aquaculture can be divided into the following five categories:
1) Biological Pollution: Fish that escape from aquaculture facilities may harm wild fish populations through competition and interbreeding, or by spreading diseases and parasites. Escaped farmed Atlantic salmon (Salmo salar) are a particular problem, and may threaten endangered wild Atlantic salmon in Maine. In the future, farming transgenic, or genetically modified, fish may exacerbate concerns about biological pollution.
2) Fish for Fish Feeds: Some types of aquaculture use large quantities of wild-caught fish as feed ingredients, and thus indirectly affect marine ecosystems thousands of miles from fish farms.
3) Organic Pollution and Eutrophication: Some aquaculture systems contribute to nutrient loading through discharges of fish wastes and uneaten feed. Compared to the largest U.S. sources of nutrient pollution, aquaculture's contribution is small, but it can be locally significant.
4) Chemical Pollution: A variety of approved chemicals are used in aquaculture, including antibiotics and pesticides. Chemical use in U.S. aquaculture is low compared to use in terrestrial agriculture, but antibiotic resistance and harm to nontarget species are concerns.
5) Habitat Modification: Marine aquaculture spreads over 26,000 marine hectares, or roughly 100 square miles. Some facilities attract marine predators, and can harm them through accidental entanglement or intentional harassment techniques.
A number of technologies and practices are available to prevent or mitigate these environmental problems. Options to make U.S. aquaculture environmentally sustainable include:
- Developing strong effluent guidelines for aquaculture under the Clean Water Act;
- Supporting National Marine Fisheries Service and Fish and Wildlife Service activities under the Endangered Species Act to protect wild Atlantic salmon;
- Establishing an environmentally protective permitting program for offshore aquaculture;
- Improving state oversight of aquaculture;
- Championing research and development investments and cost-share incentives for sustainable aquaculture practices;
- Establishing a federal approval process for transgenic fish that mandates evnironmental protection;
- Supporting market incentives for environmentally sound fish-farming;
- Developing bilateral agreements with Canada to study and minimize the impact of salmon-farming on wild salmon stocks