Do you really know what kind of fish you are eating?

If you buy fish in New York City, you'll get the type of fish you wanted only 61 percent of the time, according to a new study by watchdog group Oceana. The study, released last week, was the result of the group's latest investigation into fish fraud in major American cities. They report:

Oceana found that 39 percent of the 142 seafood samples collected and DNA tested from grocery stores, restaurants and sushi venues were mislabeled, according to the United States Food and Drug Administration (FDA) guidelines.

Apparently NYC isn't the worst offender, though. In Boston, 48 percent of fish were mislabeled, and 55 percent were mislabeled in Los Angeles. Part of the problem comes from vendors selling cheaper versions of popular fish to restaurants — most diners don't know the difference between various species of similar-tasting fish.

Do you really know what kind of fish you are eating?S

According to Huffington Post:

No seafood was mislabeled more frequently in the study than "white tuna," a staple on many sushi menus. The Food and Drug Administration's Seafood List, considered the gold standard on matters of seafood labeling, doesn't include "white tuna" as an "acceptable market name" for any species of fresh fish, but a layperson seeing that name would at least expect that it's a kind of tuna. Yet the Oceana tests found that 94 percent of samples of fish listed as "white tuna" were actually escolar, a white-fleshed fish in the snake mackerel family that has long been known to cause gastrointestinal difficulties in those who eat it.

Plus, Americans are generally ignorant of most of the hundreds of tasty fish in the sea. They prefer to order popular species like salmon or tuna, and shy away from other species whose names they don't recognize. It's possible that some of the mislabeling is done to make unfamiliar fish seem more palatable to Americans.

Read Oceana's whole study here.