Genetic markers show something fishy with certified Chilean sea bass sales

The research by Marko, Holly Nance and Kimberly Guynn is reported in the Aug. 23 edition of Current Biology (Marko et al.: “Genetic detection of mislabeled fish from a certified sustainable fishery” Vol. 21 No. 16).

The findings raise questions about the integrity of the “chain of custody” for retail fish certified to be from sustainable fisheries. Somewhere along the fish supply chain, which starts with the Marine Stewardship Council certifying that a location is a sustainable fishery and ends in a market with fish on ice eco-labeled as sustainably harvested seafood, a significant number of impostors are introduced.

Analyzing the mitochondrial DNA from fish purchased at retail outlets in eight states, the researchers found that eight percent of 36 fish sampled were “actually other species,” according to Marko, and that 15 percent of 33 fish sampled had mitochondrial DNA variants that are not known from the South Georgia/Shag Rocks population, which is the only certified Chilean sea bass fishery. The location is in the South Ocean between Antarctica and the southern tip of South America.

“Our data point to a problem with the supply chain,” said Marko. “Fish are being sold that are improperly labeled. Where and how the uncertified fish reach market was not the focus of our research but are issues that deserve attention.”

Marko has been a fish sleuth before. In 2004, he and his students at the University of North Carolina at Chapel Hill used genetic analyses to identify red snapper, finding out that a significant number of the fish sold in markets were not what were advertised.