According to findings reported Wednesday in the first statewide testing of fish from grocery stores, children and women of childbearing age should eat no more than one meal a week of those two species because of contamination with mercury, a brain poison, based on Environmental Protection Agency guidelines..

Previous reports on the levels of contamination in fish covered only those found in rivers, lakes and marine waters, so the study was ordered last year because "we really don't have a handle on what the levels are," said David E. McBride, a state toxicologist.

The Food and Drug Administration limits the level of mercury and PCBs in fish sold in retail outlets but does only limited checking, and state health officials said they considered that agency's limits too high.

Nonetheless, most fish are safe to eat in moderate amounts and a beneficial part of a regular diet, health officials emphasized.

"Fish are great food," said James A. VanDerslice, a state Health Department epidemiologist. "We want everybody to be eating the recommended two meals a week, but there are contaminants."

"Whatever you eat has good things and bad things," said Glenn Reed, president of the Pacific Seafood Processors Association. "It seems that the vast body of evidence is that seafood is one of the healthiest proteins you can eat."

For the survey, Health Department workers bought canned tuna and fresh fillets of eight species of fish to test for mercury, polychlorinated biphenyls, or PCBs, and polybrominated diphenyl ethers, or PBDEs, flame retardants that accumulate in the body.

The most mercury was found in canned albacore tuna, the subject of earlier federal warnings. According to EPA guidelines, women and children should eat no more than four cans a month.

There has been no similar federal warning about Pacific red snapper and halibut.

The lowest levels of mercury were found in catfish, pollock, salmon, flounder and cod.

Chinook or king salmon topped the list for PCBs, a long-banned chemical linked to cancer and impaired brain development, but experts remain divided on the risk.

State health officials said the salmon PCB levels were too low to pose any danger to brain development if consumed in two servings a week.

Some environmentalists noted that according to EPA guidelines, eating salmon with that much PCB more than once a month could increase the risk of cancer, but Robert M. Duff, director of the state Office of Environmental Health Assessments, said that standard is more dubious because it is based on research on animals rather than on humans.