That's part of the gastronomic advice that can be gleaned from a study released this month by two professors and an official of the state Department of Environmental Protection.

Among the conclusions is that a fillet of flounder purchased at a supermarket or fish market in New Jersey contains about one-twelfth the mercury of a similar piece of tuna. It also found that mercury levels in several types of fish purchased here were higher than estimates published by the Food and Drug Administration.

Eileen Murphy, director of the DEP's Division of Science, Research and Technology, said the study means "we need to look into contaminants in fish on a more widespread basis."

Murphy said the DEP is seeking funding for an expanded study of locally available fish that would test nine species for mercury, dioxin, PCBs and pesticides.

New Jersey was recently given high marks for reducing mercury levels in the environment by the Environmental Protection Agency. Murphy said any reduction in mercury emissions ultimately should reduce mercury levels in fish, but "there is so much in the environment now that we should still see mercury in fish for awhile."

The New Jersey study, published in the March issue of Environmental Health Perspectives, sought to measure mercury levels in fish purchased in different regions of the state.

The authors - Joanna Burger, a Rutgers professor; UMDNJ-Robert Wood Johnson professor Michael Gochfeld and Alan Stern of the state Department of Environmental Protection - were prompted to do the study because relatively little data exist about mercury levels in store-bought fish, as opposed to fish caught by recreational anglers.

Mercury readings were taken from tuna, flounder and bluefish fillets bought at 57 markets and fish markets in the northern, central, southern and coastal regions of New Jersey, and significant differences were noted in the mercury levels of the three species.

On average, fresh tuna was found to have a mercury level of .64, which represents parts per million or micrograms per gram. Flounder weighed in at .05 and bluefish at 0.26.

Perhaps more significant, the mercury level in the tuna fillets tested was 68 percent higher than the FDA's estimate of .38. The federal agency's estimates are based on data gathered between 1990 and 1992, while the fish in the New Jersey study were tested in 2003.

There was little or no difference between FDA estimates and the study's results for flounder and bluefish.

The authors suggested the state publish updated information that lists fish with high and low levels of mercury. Previously published guidelines have only considered fish caught locally by recreational anglers.

"With few exceptions, state advisories do not provide information on the risk from consuming fish purchased commercially," the study said.

DEP Commissioner Bradley Campbell has said his department will look at the risks from commercial fish in its future public health advisories.