If you eat seafood, even occasionally, there’s a good chance you’ve been served a fish species you didn’t order.

A new monthslong investigation by ocean advocacy group Oceana finds widespread and persistent fraud in the U.S. seafood industry. The organization tested 449 fish from more than 250 restaurants, seafood markets and grocery stores across the country and found that 21 percent of samples were mislabeled.

In two restaurants in Florida, cheap imported Asian catfish and spinycheek grouper, a species found only in the Indian Ocean, was sold as hogfish. In Washington, D.C., sea bass on a restaurant menu turned out to be farmed tilapia. And at a grocery store in Springfield, Virginia, Greenland turbot was labeled Alaskan halibut.

Mislabeled seafood is a rampant problem around the globe ― one that Oceana has been looking at for nearly a decade. In a 2013 analysis, the group found that as much as one-third of fish sold in the U.S. was mislabeled.

The new study did not include the 13 types of imported seafood covered by the federal Seafood Import Monitoring Program. Established in 2018, the program aims to combat illegal fishing and mislabeling by requiring imported tuna, king crab, shrimp and other seafood at high risk of fraud to contain key traceability data about harvest and shipment. Oceana opted to exclude those species from its latest review to “expose any gaps in current policy,” the authors note.

The extent to which fraud continues to occur in U.S. restaurants and markets is shocking, said Kimberly Warner, an author of the report and a senior scientist at Oceana.

“Finding domestic seafood that has been swapped out with foreign seafood seems particularly troubling as we’re trying to support our domestic fishermen,” she told HuffPost. “People are being undercut when imported seafood are taking their place and driving down the prices.”

One-third of the vendors Oceana visited between March and August of 2018 sold mislabeled products. Of the species tested, sea bass had the highest mislabeling rate, at 55 percent, followed by snapper at 42 percent. In the Great Lakes area, imported species from Asia and Europe were marketed as locally caught yellow perch.