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 labeling 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 percent 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 2013-2014.

When the authors combined the two study samplings, they found that time of year was a strong indicator of whether a restaurant would sell mislabeled 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 mislabeled 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. Ms. 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.