A recent study conducted by researchers at Seattle Pacific University sought to examine the extent of salmon mislabeling in Washington state, an important supplier of Pacific salmon globally.

Significant rates of salmon mislabeling have been observed in Washington in the past, with one study conducted in 2009–2011 reporting 20 percent of salmon samples from grocery stores and restaurants to be misrepresented. To address this known problem, in 2013, Washington state House Bill 1200 was passed, making it unlawful to knowingly sell any fish or shellfish products without identifying its common name, as well as prohibiting the sale of any salmon at retail without identifying it as wild-caught Pacific salmon or farm-raised Atlantic salmon.

To investigate whether legislative efforts have reduced salmon mislabeling rates over the past decade, the present Seattle Pacific University study collected and tested 119 salmon samples from 67 grocery stores and 52 sushi restaurants in Seattle, Washington during 2023. DNA sequencing was used to identify the fish species of each sample.

Overall, the researchers found mislabeling fraud among 18 percent of salmon samples from both grocery stores and sushi restaurants—a 13.5 percent mislabeling rate was seen at grocery stores, versus a 23.1 percent mislabeling rate in sushi restaurants. Of the 13.5 percent mislabeled salmon at grocery stores, 9 percent were vendor-claimed wild Pacific salmon being substituted with a different wild Pacific salmon species than labeled, 3 percent were vendor-claimed farmed Atlantic salmon substituted with wild Pacific salmon species, and 1.5 percent were vendor-claimed farmed Atlantic salmon substituted with steelhead trout. Of the 23.1 percent mislabeled salmon at sushi restaurants, 19.2 percent were vendor-claimed wild Pacific salmon substituted with farmed Atlantic salmon, and 3.8 percent were vendor-claimed wild Pacific salmon substituted with a different wild Pacific salmon species.

Additionally, Seattle sushi restaurants often sold farmed salmon mislabeled as wild salmon. Analysis of only the vendor-claimed wild salmon samples revealed a stark difference between retailer types in the substitution of wild salmon with farmed salmon, with sushi restaurants having an overall higher mislabeling rate of 32.3 percent (10 of 31 samples), versus 0 percent (of 52 samples) at grocery stores. Moreover, wild salmon was substituted with another salmon species (wild or farmed) in 38.7 percent (12 of 31) of sushi restaurant samples compared to 11.1 percent (6 of 54) of grocery store samples.

The economic loss to customers resulting from salmon mislabeling was much worse at sushi restaurants than grocery stores, according to the researchers’ analysis. All fraudulent salmon sold at sushi establishments were actually a cheaper market-priced fish, whereas the same trend was not detected at grocery stores.