(Newser) – OK, it's not horse meat, but fish mislabeling is rampant across the US, a 20-state study finds. Up to a third of restaurant and grocery-store seafood is labeled incorrectly, the Washington Post reports. Looking at specific varieties, the figures get even starker: Some 94% of so-called tuna in New York wasn't, the New York Times reports, while 87% of snapper is mislabeled. “Even a relatively educated consumer couldn’t look at a whole fish and say, ‘I’m sure that’s a red snapper and not lane snapper,’ ” says the study's lead author. The study follows up on a smaller one released in December by activist group Oceana.

Overall, Southern California had the worst labeling record, with 52% of its fish marked wrong. And the worst venue for wrong labels: sushi restaurants, the study found, at a 95% rate. In many cases, sushi joints called escolar—or albacore canned tuna—"white tuna." Too much of it can cause diarrhea. Odds for consumers are best at grocery stores, where 27% of the products are mislabeled. In many cases, cheaper fish took the place of more expensive ones. Less than 1% of seafood sold in the US undergoes FDA testing for fraud, says a 2009 report. (Read more fish stories.)

