SEATTLE—An Oceana investigation of salmon marketed during the winter months in the Midwest and East Coast found 43 percent of this fish mislabeled.

Most often, Atlantic farmed salmon was falsely marketed as wild salmon, and restaurants mislabeled this fish much more frequently than grocery stores and retail markets.

The investigation was based on 82 samples collected in Chicago, New York, Washington and Virginia, and all were analyzed to determine their salmon species.

An earlier, and broader, Oceana survey of 384 salmon collected during the peak of the 2012 summer salmon season found that only 7 percent of the sampled fish was mislabeled.

The more recent survey during the winter of 2013-14 came at a time when the summer harvests are long over, and fresh wild salmon is hard to find while fresh farmed salmon, which is harvested year-round, remains abundant.

Oceana is a nonprofit advocacy group that focuses on oceans, fisheries and other marine issues and has campaigned against the environmental impacts of salmon farming.