Fish farming (a.k.a. aquaculture) looks at first glance like a sure-fire way to take some pressure off the world’s overfished oceans. Not necessarily, warn Naylor, a senior research scholar at Stanford University’s Center for Environmental Science and Policy, and her nine co-authors. The problem, they explain, is that some aquaculture increases the pressure on ocean fisheries.

Aquaculture has grown rapidly in recent years, producing 29 million metric tons of farmed fish and shellfish in 1997, more than twice the tonnage of a decade earlier (but still no more than a third or so of the 85 to 95 million metric tons of wild fish caught each year.) Roughly 90 percent of the world’s fish farming is done in Asia, particularly China. Family and cooperative farms raise carp for local or regional consumption, while commercial farms produce salmon, shrimp, and other highly valued fish for tables in Europe, North America, and Japan.

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