NEW YORK, Oct 29 — The wild-caught salmon sold by restaurants and fishmongers is frequently farm-raised fish that has been mislabelled, said a report released yesterday.

Using DNA analysis, the non-profit ocean conservation group Oceana studied 82 samples and found that two-thirds of the salmon appearing on restaurant menus were incorrectly labelled. Twenty per cent of salmon from groceries was incorrectly identified, the group found.

Overall, 43 per cent of the salmon the group collected — in New York, Washington, Chicago and Virginia, from upscale and takeout restaurants, and from various neighbourhood and chain groceries— was misidentified. The researchers reported that the most common mislabelling in their survey involved Atlantic salmon being sold as “wild salmon.” The group also found instances of chum salmon being advertised as costlier king salmon, and of rainbow trout sold as wild salmon.

The study’s authors recommended that new policies be created to protect seafood consumers and honest fishermen from mislabelling.

Oceana performed similar investigations of fish in 2013, shrimp in 2014 and crab cakes earlier this year.

The most recent study is a follow-up to a nationwide survey of salmon labelling published by the group in 2013.

“Our results are consistent and wide enough to know that this is a problem that can occur anyplace, anytime, with any type of seafood,” said Kimberly Warner, a senior scientist at Oceana and an author of the report.

The earlier salmon study found lower rates of substitution, only 7 per cent of 384 samples, which the group attributed to the different seasons in which the studies were conducted. The first study looked at salmon sold at the height of the commercial fishing season in 2012, while samples for the most recent report were collected out of season, during the winter of 2013-14.

When the authors combined the two study samplings, they found that time of year was a strong indicator of whether a restaurant would sell mislabelled salmon. During winter months, fresh wild salmon is less available, but diners’ appetite for the fish does not diminish, creating an incentive to substitute readily available farmed salmon. The researchers found that large chain groceries had the lowest percentage of misidentified salmon, and were eight times less likely to offer such mislabelled salmon than small groceries.

The findings came as no surprise to Christa Hoover, the executive director of Copper River/Prince William Sound Marketing Association, which represents fishermen in Alaska who wrangle wild salmon. Hoover has seen several examples of faux Alaska Copper River salmon on the market, and said she hoped such studies would help government officials enact stronger label legislation.

“They need to know that this isn’t just anecdotal evidence, that our salmon is being plagiarised with farmed salmon and this DNA evidence shows that,” she said.

Consumers looking to protect themselves from purchasing the wrong types of salmon should ask their sellers about its exact point of origin, its species, and whether it is fresh or previously frozen, the authors suggested. — The New York Times