Three quarters of the fish sold in the U.S. as red snapper may be a different species, researchers report today in the journal Nature. In addition to tricking customers, the false labels could misrepresent the threat posed by overfishing.

Red snappers dwell in offshore waters in the Gulf of Mexico and are the most fished of all snappers. Concerned for their viability, the Gulf of Mexico Fishery Management Council and the U.S. Department of Commerce called for restrictions on the number of red snapper catches in 1996. But demand remains high, making the red snapper the priciest of the snapper group.

In the U.S., only Lutjanus campechanus can be legally sold as red snapper. Suspecting that the restrictions might foster substitution of the costly fish with its less valuable relatives, Peter B. Marko of the University of North Carolina at Chapel Hill and his colleagues genetically tested 22 purported red snappers from eight states. The team compared the DNA sequences of their sample fish to standards from GenBank, the genetic library of the National Center for Biotechnology Information.

The researchers verified that five of the fish were indeed L. campechanus, but the rest belonged to other snapper species. A few of the stand-ins inhabit the same waters as the red snapper, which may indicate that they were misidentified--purposefully or inadvertently--on the boat or at the dock. Because fishery managers sometimes rely on fishing industry reports, these errors could affect estimates of stock size, both of the desirable and the not-so-desirable species.

More than half the snappers in the study hailed from other parts of the world or were not found in GenBank. These may have been imported fish whose labels were switched by a retailer somewhere along the commercial chain. The authors contend that the false advertising distorts the public's perception. Says Marko, "The consumer might think, 'How can red snapper be endangered when I see it in the store all the time?'" --Michael Schirber