Buyer beware: Your salmon may be lying to you. In a study published today, researchers found evidence that these products are regularly mislabeled as wild salmon when they are actually farmed salmon, which could be especially costly for sushi restaurant customers.

Mislabeling of salmon and seafood it’s been a known problem for some time — so much so that Washington state, where the salmon industry is particularly importantpassed a law in 2013 aimed at reducing this and other types of fish fraud. Senior researcher Tracie Delgado, a biology professor at Seattle Pacific University, had read previous studies on the topic and knew about the 2013 law, so she decided to have students in her genetics lab course investigate for themselves whether things had improved since then. .

“We had no idea what the results would be when we started this project, and we were very surprised by the results,” Delgado told Gizmodo. “Despite Washington state legislation making salmon mislabeling illegal, salmon mislabeling fraud is still a problem in Seattle.”

Delgado and her students collected and analyzed DNA from salmon samples from 67 grocery stores and 52 sushi restaurants in the Seattle area between fall 2022 and fall 2023. In total, 18 percent of those samples were mislabeled. The team’s conclusions were published Wednesday in the diary PLOS-One.

Although mislabeling was relatively common in both grocery stores and restaurants, it was ultimately a more serious problem. About one-third of restaurant samples were mislabeled as wild salmon instead of farmed, for example, compared with zero such mislabeled samples from grocery stores. And sometimes sushi samples marketed as a specific species of wild salmon were instead a different wild species, although this also happened in grocery stores (the combined wild and wild salmon mislabeling rate was 38% in restaurants and 11% in shops).

On the bright side, the researchers found no cases of farmed salmon being mislabeled as wild in grocery stores. This suggests that Washington’s seafood identification laws have done at least a little to mitigate fraud. But the overall salmon mislabeling rate found in this study is consistent with some previous estimates of Washington’s mislabeled rate before the 2013 law, while subsequent studies have found even higher rates in other states. And the costs of mislabeling salmon at sushi restaurants are almost certainly passed on to customers, as some people will end up paying more for “wild” salmon that should actually be cheaper farmed salmon (that said, this effect potential proved to be insignificant). in grocery stores).

Salmon mislabeling is also likely to have a negative impact on the environment, according to Delgado.

“Dishonest reporting of catch data and mislabeling of seafood complicates fisheries conservation efforts because it prevents accurate tracking of supply chains and complicates effective fisheries management efforts,” she said. “Therefore, fisheries managers may erroneously conclude that wild salmon stocks that are effectively depleted persist at sustainably harvestable densities.”

More needs to be done to stop salmon and other seafood fraud, researchers say, such as encouraging restaurants to periodically test that the fish they’re getting is the real deal. Is there a existing inspection program set up by the National Oceanic and Atmospheric Administration for fishing boats, processors and retailers to test their fish, Delgado notes, although participation is voluntary. And while sushi customers may not be able to physically smell the mislabeled fish, they too can take steps to reduce their chances of being defrauded at least.

“Customers can ask sushi restaurants if they have a quality control process that confirms salmon identification and if they have reliable suppliers from which the sushi restaurant sources,” Delgado said. “Customers can also ask sushi restaurants if they buy the salmon whole and then filet the salmon at the restaurant,” or if the resulting salmon is already processed. “If the salmon is filleted fresh at the restaurant, then a good sushi chef would know the difference between wild salmon and farmed salmon by looking at it,” she explained.

Ultimately, however, it will likely require the adoption and enforcement of stricter seafood fraud laws to effectively curtail this practice.