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Carnivorous fish nibble at farming gain

Fish farming overall may be supplementing the wild stocks, but for certain species, the farms cause a net loss of wild fish, warns a broad new review.

Some aquaculturists use up to 5 kilograms of wild fish as feed to grow 1 kg of carnivorous species like seabass and salmon, notes economist Rosamond L. Naylor of Stanford University.

Such appetites for feed plus other environmental side effects undermine potential aquaculture benefits, she and her colleagues conclude in the June 29 Nature.

Crops of farmed fish and shellfish have doubled in just 15 years, Naylor notes. "Many people believe that such growth relieves pressure on ocean fisheries, but the opposite is true for some types of aquaculture," the authors caution.

The 10 coauthors represent diverse expertise including aquaculture biologists and environmentalists. They produced a unique evaluation of whether seafood farms, which raise 220 species, add to world fish supplies, Naylor says.

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