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With marine capture fisheries stagnant, marine fish farming can supply rising demand, but sustainable practices must reduce current levels of environmental damage.

Due to population growth and rising incomes, consumption of fish more than tripled from 1961 to 2001, rising from 28 to 96 million tonnes. Much of the increase was fuelled by consumption in developing countries (IFPRI and WorldFish Center 2003). With threequarters of the world’s wild fish stocks fully or overexploited, a number of countries are turning to fish farms to meet the rising demand for fish and shellfish. Aquaculture, dominated by freshwater species (Figure 1), has grown at an average annual rate of nine per cent since 1970, compared with three per cent for livestock meat and one per cent for captured fish over the same period. Nearly one-third of the fish consumed by humans is now produced by fish farms, with China, India and other Asian countries accounting for 87 per cent of global aquaculture production by weight (IFPRI and WorldFish Center 2003).

Africa is the only continent where per capita fish supplies have barely changed in recent decades – from 10.3 kg per person in 1973, to 10.5 kg in 2002 (FAO 2005a). However, African aquaculture could increase dramatically. At a summit held in Nigeria in August 2005, leaders of 25 African nations signed a resolution calling for rapid investment in fish farms as a means to reduce poverty and hunger (von Bubnoff 2005).

Farming of marine species – or mariculture – is growing rapidly. Across the globe, from Chile to China and Scotland to South Africa, farming of salmon, shrimp, mussels, oysters and clams is increasingly common. Atlantic cod farms have recently opened in Iceland and Norway. Sea bream and sea bass are increasingly cultivated in the Mediterranean. In Mexico, Spain and Australia, farms now fatten wild-caught tuna. In the waters off the coast of the Northeastern United States, pilot studies are underway to farm halibut, haddock, flounder and other species.

While mariculture has the potential to supplement the world’s supply of edible protein, current practices often create significant environmental problems and even reduce the overall supply of fish protein. Fertilizer, undigested feed, biological waste and veterinary drugs used in mariculture are released into the oceans and surrounding waterways. Farms create conditions for the spread of disease and parasites and, through the escape of farmed fish, introduce invasive species. Through competition for food or habitat, these exotic species threaten native species or alter entire ecosystems.

Coastal farming, particularly for shrimp, has destroyed thousands of hectares of mangrove forests, which filter water, reduce erosion, serve as critical hatcheries for fish, and protect coastal communities from storms and floods (IFPRI and WorldFish Center 2003). Several mariculture systems are in use or under development in Asia, Africa, Europe and the Americas. They include net pens in coastal and offshore areas, ocean ranching, nonfeeding or extractive culture and intensive shrimp farming. Each system offers food production benefits but also has the potential to create environmental damage – both of which can be improved through effective policy responses.

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