According to a new study by researchers at the University of California Los Angeles and Loyola Marymount University, nearly half of the fish served at more than two dozen highly-rated sushi restaurants in the city is mislabeled. The study published on Wednesday in the journal Conservation Biology.
The study, whose findings were announced Wednesday, checked the DNA of 364 samples of 10 popular fish varieties ordered at 26 L.A. sushi restaurants from 2012 through 2015 and found that 47 percent of the sushi was mislabeled. Biology students at UCLA were sent out to the restaurants over the four years to collect the samples.
A UCLA professor who led the study, Paul Barber said, “Half of what we’re buying isn’t what we think it is. Fish fraud could be accidental, but I suspect that in some cases the mislabeling is very much intentional, though it’s hard to know where in the supply chain it begins. I suspected we would find some mislabeling, but I didn’t think it would be as high as we found in some species.”
Demian Willette, a researcher and co-author of the study, said that while mislabeling of food is nothing new, what was surprising was that it would be so prevalent, especially in a food-conscious market like Los Angeles. “We didn’t really expect that because Los Angeles is a very foodie culture and in general people are very conscious about what they eat,” he said.
The good news is that sushi represented as tuna was almost always tuna. Salmon was mislabeled only about 1 in 10 times. But out of 43 orders of halibut and 32 orders of red snapper, DNA tests showed the researchers were always served a different kind of fish. Yellowfin tuna was also swapped on seven out of nine orders, usually for bigeye tuna, a vulnerable and overexploited species.
“In some cases, the same restaurant was substituting multiple fish on menus,” Mr Willette said. “So say they would propose three types of tuna when they actually served the same type.”
He said halibut was often swapped for cheaper species of flounder considered overfished or near threatened while red snapper was substituted for sea bream. He added that while price was a factor in the apparent fraud that likely involving wholesalers, attempts to skirt fishing policies also played a part. “Some of it is price, and some of it is regulations,” he said.
Researchers said that 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.
The researchers did not release the identity of the sushi restaurants involved in the study, in part because they expect that most sushi restaurants would fare similarly.
While the study took place in Los Angeles, researchers said, it aligns with similar results in previous studies in other locations as well.
The study warned that apart from duping consumers, the mislabeling posed a health risk for people with allergies to certain fish and for pregnant women and children who should avoid high-mercury fish. “A common parasite found in raw olive flounder… has caused ‘rampant’ food poisoning in Japan,” the study noted.
According to UCLA press release, here’s what the study found.
Over the course of the study, conducted from 2012 through 2015, only bluefin tuna was always sold as advertised. While researchers found 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, said Barber, who worked with lead author Demian Willette and researchers from UC Santa Cruz and UC Santa Barbara. Willette is a UCLA assistant research scientist and a Loyola Marymount University biology instructor.