A New Study Finds Mislabelled Fish

A new study from researchers at UCLA and Loyola Marymount University checked the DNA of fish ordered at 26 Los Angeles sushi restaurants from 2012 through 2015, and found that 47 percent of sushi was mislabelled.  Salmon was found to be mislabelled one in 10 times, and out of 43 orders of halibut and 32 orders of red snapper they were all a different kind of fish. A one-year sampling of high-end grocery stores found similar mislabelling rates.

“Half of what we’re buying isn’t what we think it is,” said Paul Barber, a UCLA professor of ecology and evolutionary biology and senior author of the study that appeared today in the journal Conservation Biology. “Fish fraud could be accidental, but I suspect that in some cases the mislabelling is very much intentional, though it’s hard to know where in the supply chain it begins. I suspected we would find some mislabelling, but I didn’t think it would be as high as we found in some species.”

The fraud undermines environmental regulations limiting overfishing, introduces unexpected health risks and interferes with consumers’ decisions. Over the four-year study, only bluefin tuna was always exactly as advertised. Different kinds of tuna occasionally swapped places, including samples of species classified as endangered and critically endangered. Out of nine orders of yellowfin tuna, seven were a different kind of tuna. Salmon had 6 of 47 orders going awry. However, all halibut and red snapper orders failed the DNA test, and in 9 out of 10 cases, diners ordering halibut were served flounder. About 4 in 10 halibut orders were species of flounder considered overfished or near threatened.

Some short-term studies have suggested that fish fraud is declining due in part to stricter regulations, but this study uncovered consistent mislabelling year over year. Previous studies detected similar problems nationwide, suggesting that the UCLA findings are widely applicable.

“If we don’t have accurate information on what we’re buying, we can’t make informed choices,” Barber said. “The amount of mislabelling is so high and consistent, one has to think that even the restaurants are being duped.”

For diners who wish to avoid high-mercury fish, such as pregnant women or small children, mislabelling could harm their health. Some fish are riskier than others, with common parasites being found in raw olive flounder. The researchers used DNA barcoding, which uses a partial DNA sequence from a mitochondrial gene, to accurately identify the fish.

“DNA barcoding is becoming an increasingly popular tool to identify mislabelled products,” said author Demian Willette. “Our finding of a persistently high rate of seafood mislabelling should encourage consumers to demand strong truth-in-menu laws from local public health agencies. Citizen-science and crowd-sourced data also have real potential to keep the consumer informed.”

While some mislabelling could be unintentional, fraud could also result from the desire to skirt environmental regulations or the ability to sell a cheaper fish as a more expensive product. The global fish trade is a $135 billion industry, the study notes. New federal regulations governing monitoring of seafood imports went into effect Jan. 9 to address the problem. The UCLA study shows increased monitoring is needed, said Sarah Sikich, vice president of the environmental group Heal the Bay.

Please note: The content above may have been edited to ensure it is in keeping with Technology Networks’ style and length guidelines.