WASHINGTON — On the heels of the European horse meat scandal comes a new report of food fraud in the United States.

A recent investigation of fish fraud found one-third of 1,215 seafood samples collected in 21 states were mislabeled per U.S. Food and Drug Administration guidelines.

“Purchasing seafood has become the ultimate guessing game for U.S. consumers,” said Beth Lowell, campaign director at international advocacy group Oceana, who conducted the study. “Whether you live in Florida or Kansas, no one is safe from seafood fraud. We need to track our seafood from boat to plate so that consumers can be more confident that the fish they purchase is safe, legal and honestly labeled.”

The investigation focused on regionally significant fish as well as commonly mislabeled seafood, such as red snapper, cod, tuna and wild salmon. Snapper and tuna reeled in the highest mislabeling rates, at 87% and 59%, respectively. Only 7 of the 120 red snapper samples collected were correctly labeled.

Seventy-four per cent of sushi venues examined were found to mislabel its seafood selection, followed by 38% of other restaurants and 18% of grocery stores in the study.

“Some of the fish substitutions we found are just disturbing,” said Kimberly Warner, report author and senior scientist at Oceana. “Apart from being cheated, many consumers are being denied the right to choose fish wisely based on health or conservations concerns.”

For example, 84% of the white tuna samples were actually escolar, which may cause digestive issues for some.

Additionally, fish on the F.D.A.’s “do not eat” list for pregnant women and children, including tilefish and king mackerel, were sold as such safer species as red snapper, halibut and grouper.

The investigation also found that cheaper farmed fish, including pangasius, tilapia and Atlantic farmed salmon, were swapped for wild fish, and overfished species were sold as more sustainable catches.