NEW YORK, NY January 23, 2008 —There's so much mercury in tuna sushi sold at some New York City restaurants, that New Yorkers would ingest more of the toxic metal than the federal government recommends, if they ate six pieces a week.

REPORTER: Lab tests commissioned by the New York Times also found five of 20 restaurants had mercury levels high enough to cause the feds to yank the fish from the market.

Tim Fitzgerald, a marine scientist with the advocacy group, Environmental Defense, says people shouldn't stop eating fish altogether. They should focus instead on smaller fish in the food chain, such as mackerel, anchovies, and sardines.

FITZGERALD: I actually like the little stinky fish. They have really great flavor and a lot of times they are actually less expensive. I think a lot of people have the impression that sustainable seafood is automatically more expensive and that's definitely not the case.

REPORTER: He says mackerel, anchovies, and sardines are low in contaminants, high in omega 3's and farmed or caught in a responsible way.