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A recent study found that American restaurants and grocery stories routinely mislabel fish.Fred Lum/The Globe and Mail

Seafood fraud is rampant in the United States, where one third of fish samples were mislabelled, according to a new report based on Canadian lab testing.

The study by Oceana, a sea-life conservation group, found that consumers were regularly hoodwinked into buying seafood that was not as advertised. For instance, fish sold as white tuna was often escolar, so-called Atlantic cod was either Pacific cod or white hake, and snapper was a false label for a long list of inferior substitutes, including seabream, tilapia or rockfish.

"Dishonest practices are allowing this to happen and the consumer needs to demand that seafood that they eat is safe, legally caught and honestly labelled. I don't think that's too much to ask," said Kimberly Warner, a senior scientist at Oceana who wrote the report. "I think our government and governments worldwide need to step up to the plate and demand that our seafood is traceable."

The investigation, which used a University of Guelph lab to conduct DNA analysis of seafood samples, backs up earlier reports that have also found staggering evidence of fish fraud. A 2008 study done by the same lab found that 25 per cent of seafood was mislabelled in Toronto and New York.

"What's happening here is likely happening elsewhere as well and research thus far has really supported that," Ms. Warner said.

The Oceana study, which is billed as one of the largest seafood fraud investigations ever in the world, found that 33 per cent of 1,215 fish samples collected from 674 retail outlets in 21 states were improperly labelled. Researchers collected samples from supermarkets, fishmongers and restaurants, including sushi bars.

In many cases, farmed fish were substituted for more expensive wild seafood. But consumers who chose sustainable fish were sometimes served vulnerable species. And some of the substitutions carried health risks, such as when fish with high mercury levels were sold under the guise of safer species.

"People are not only getting cheated but they could potentially be putting their health at risk with this type of mislabelling," Ms. Warner said.

Seafood's complex supply chain makes it difficult to pinpoint whether the fraud occurs at the level of fishermen, processing plants, distributors or points of sale, the study says. As well, it notes that more than 90 per cent of the seafood eaten in the U.S. is imported and less than 1 per cent is inspected by the government specifically for fraud.

Among the study's findings:

  • Sushi restaurants had the highest rates of mislabelling, at 74 per cent. Grocery stores were the best, with 18 per cent selling mislabelled fish.
  • Snapper was the most commonly mislabelled species, at 87 per cent. And only seven of 120 red snapper samples tested were as advertised.
  • 84 per cent of white tuna samples were actually escolar, which can cause digestive problems.
  • Cheaper farmed fish are often substituted for wild species, such as tilapia sold as red snapper and Atlantic farmed salmon sold as wild or king salmon.
  • Overfished and vulnerable species were also sold instead of more sustainable choices, such as Atlantic halibut masquerading as Pacific halibut.
  • Fish with high levels of mercury, which should not be eaten by pregnant women and children, were sometimes sold under the guise of safer fish. For instance, consumers in New York City who selected red snapper and halibut were instead sold tilefish.
  • Southern California had the highest rates of fraud, at 52 per cent of samples.

Editor's note: The article originally said 44 per cent of grocery stores were selling mislabelled fish. In fact the study says the percentage is 18.

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