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takyon writes:

University of California, Los Angeles and Loyola Marymount University researchers tested the DNA of fish ordered at 26 Los Angeles sushi restaurants from 2012 to 2015, and found that 47% of the sushi was mislabeled. Tuna and salmon were generally genuine, but halibut and red snapper were mislabeled in every single instance of 43 and 32 orders, respectively:

A one-year sampling of high-end grocery stores found similar mislabeling rates, suggesting the bait-and-switch may occur earlier in the supply chain than the point of sale to consumers. [...] Over the four-year study, only bluefin tuna was always exactly as advertised. While only one of 48 tuna samples was not tuna, different kinds of tuna occasionally swapped places, including two samples that turned out to be Atlantic bluefin tuna and southern bluefin tuna, species classified as endangered and critically endangered. Out of nine orders of yellowfin tuna, seven were a different kind of tuna, usually bigeye — a vulnerable and overexploited species, the researchers said. Salmon remained a largely safe bet, with only 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.

Although some short-term studies have suggested that fish fraud is declining due in part to stricter regulations, this study uncovered consistent mislabeling year over year, indicating seafood misidentification is not improving. While the current study took place in Los Angeles, previous studies detected similar problems nationwide, suggesting that the UCLA findings are widely applicable [...] The researchers used DNA barcoding, which uses a partial DNA sequence from a mitochondrial gene, to accurately identify the fish.

Also at CBS Los Angeles.

Original Submission