She's not the only one. A flood of conflicting and often inflammatory information has confronted salmon lovers since the publication in January of a study reporting that tests of 700 salmon samples from around the world showed farmed fish with consistently higher levels of polychlorinated biphenyls, or PCBs, than wild fish have. The study, published in the journal Science, also found dioxins and other dangerous chemicals in salmon. And this came on the heels of reports of mercury contamination in fish, including salmon.

As with other controversies involving the food supply, commerce and science, the issue is as convoluted and puzzling as the spawning path of the wild salmon.

Isabella Scherer, a native Alaskan who lives in Honolulu, grew up eating wild salmon raw — that's the way the Sugpiaq natives like it — and says farmed fish pose a threat to both the world's fish supply and her people's livelihood.

She worries that aquaculture operations pollute waters, that fish farms near wild-salmon migration routes spread diseases to wild fish, and that escaped farm-raised Atlantic salmon compete with wild fish or alter their gene pool. She also notes that farmed fish is much cheaper to produce, creating stiff competition for wild salmon, which can be twice or three times the price.

"People here don't know there's a big difference between farmed-raised and wild, and it's not just the price," said Scherer, who sells frozen-at-sea wild salmon under the Sugpiaq label (see accompanying story).

Health benefits proven

His approach is to check out the science, then make a choice — and avoid eating too much of any one food. The Japanese government's dietary guidelines specify selections from a wide range of food groups, and that's wise advice, he said.

Buyer Gary Ishimoto of Diamond Head Seafood sighs when asked about farmed salmon. He sees the issue in terms of supply and demand. Suppliers and consumers both demand consistency — consistent quality and consistent price, he said. Farm-raised salmon provides that because it's a year-round product very much under the control of the aquaculture industry — down to manipulating the color of the flesh by means of feed additives.

He expects the price of wild salmon to go up as demand increases, which might drive consumers away from the fish altogether. And he points out that the wild-salmon industry isn't free of market manipulation: "The perfect example of this is Copper River salmon. That is a full-on, 1,000-percent-awesome marketing job, taking a fish and branding it. But if you put it side by side with other wild-caught salmon, I would say the average person would have a difficult time distinguishing the two," he said.

Worldwide popularity

Chef George Mavrothalassitis, a seafood fanatic, says he doesn't like farm-raised salmon for another reason: To him, the fish are flavorless and unpleasantly oily. His Chef Mavro restaurant on King Street features primarily local fish, so he doesn't serve salmon, the sole exception being a version of lomi salmon he sometimes makes, and for that he uses costly wild salmon.

"Thirty years ago, (salmon) was one of the best fish you could find anywhere in the world, but now the reputation of the fish has been totally destroyed" (by farmed fish), he said. "Why you want to eat something just because it's cheap, I don't know."

Still, salmon is the third-most-consumed fish in the world, and farmed salmon account for most world trade in salmon, according to a study published in Environment magazine. Salmon farming — raising fish in net pens in offshore waters — originally was seen as a way to protect wild stocks from overfishing and to make the popular fish more widely available. Then came the environmental concerns, along with news of contamination, mostly focused on PCBs.

PCBs are a group of man-made industrial chemicals that have not been produced in America since 1977 but are widely used as coolants and lubricants in transformers and other electrical equipment.

The presence of PCBs and other contaminants in farmed fish is probably because the fish are fed a pellet food made from trash fish. The oceans are contaminated with chemicals from water runoff, and these have been ingested and stored in the fat and internal organs of fish.

So while the flesh of wild fish often contains these chemicals, the diets of farmed fish seem tailor-made to produce higher concentrations of these agents. The Environmental Working Group reports that farm-raised salmon may be the most concentrated source of PCBs in the world's diet.

Seeking safe eating

Q. How contaminated is farmed salmon?

A. The Science study found that the average level of PCBs in samples of farm-raised salmon was 36.6 parts per billion, while wild salmon averaged 2 to 4 parts per billion. The farmed salmon levels are in excess of the Environmental Protection Agency guidelines of 24 to 48 parts per billion but well below the Food and Drug Administration standard of less than 2,000 parts per billion.

The stricter EPA rule is a based on the amount of PCBs that are thought to be capable of causing one additional cancer case in 100,000 people over a 70-year lifetime. The study found a difference in contamination between growing areas, with European farmed salmon more contaminated than salmon raised in the Pacific.

In addition, the average dioxin level for farm-raised salmon was 1.88 parts per billion, compared with 0.17 parts per billion in wild salmon. Dioxin is a general term for a family of chemicals (including those active in Agent Orange and the pollution of Love Canal) that the EPA considers a serious health threat.

Intuitively, we cringe at the idea of consuming toxins, but we eat them more often than we know, said Dr. Laurie Steelsmith, a Honolulu naturopathic physician. Studies of healthy people with no connection to chemical industries have found that many of us harbor contaminants in our tissues, she said.

Q. How dangerous are PCBs?

A. PCBs are toxic to animals and humans if ingested in large quantities, and animal studies have shown that the chemicals have an adverse effect on the liver and can cause cancers. There are no long-term human studies that conclusively indicate that PCBs cause cancer in humans. However, the EPA sees PCBs as "probable" human carcinogens, the International Agency for Research on Cancer classifies PCBs as "probably" carcinogenic to people, and the National Toxicology Program calls PCBs "reasonably anticipated" human carcinogens, as does the U.S. Department of Health and Human Services.

Q. How much salmon is safe?

A. The EPA and the researchers in the Science study suggest eating farmed salmon no more than once a month and limiting wild salmon to eight times a month.

The FDA, however, encourages the consumption of fish, and does not plan to change this recommendation on the basis of the Science study, said spokesman Laura Alvey.

The American Heart Association recommends eating two fish meals a week from varied sources because fish is high in heart-healthy omega-3 fatty acids.

Hawai'i physician, writer and researcher Dr. Terry Shintani says his strong preference is for a plant-based diet. And while he acknowledges the cholesterol-fighting effects of omega-3 fatty acids in salmon, he isn't a big fan of the fish, because it's high in fat and calories. "The fat in salmon ranges from 40 (percent) to 50 percent; a chicken thigh with the skin off is about 48 percent fat. Neither of them are great if you're thinking of weight loss."

His recommendation: Fish is better than meat. White, firm-fleshed fish is better than oily fish (such as salmon or black cod, known locally as butterfish). And wild fish is better than farmed.

Ingestion of chemicals and heavy metals are of particular concern to pregnant women, lactating mothers and young children; PBCs have been shown to interfere with fetal brain development. But moms and kids need omega-3 fatty acids because they not only protect against heart disease but also play a role in fetal development, said Dr. Brijit Reis, a Kailua family-medicine practitioner. Because contaminants concentrate in fatty tissues, Reis suggests limiting fatty fish to once a month, substituting plant foods rich in omega-3s, including flax seed and walnuts.

Steelsmith, like Reis, offers her patients fish consumption guidelines. Fish with the lowest levels of contamination include wild salmon, scallops, sardines, shrimp, sole and farmed tilapia, she said. Chunk light tuna, halibut, cod and catfish can be eaten in moderation. She suggests avoiding farmed salmon, albacore tuna and marlin.

Q. Can pen-raised salmon be made safer?

A. Fish buyer Ishimoto is seeking out Pacific Northwest farms that are attempting a cleaner, greener method of raising salmon: placing fewer fish in each pen, eliminating antibiotics, growth hormones and other feed additives, and so on. There is no organic certification protocol for fish farming at present, he said, but some farms have succeeded in taking a more environmentally friendly approach.

Dr. David O. Carpenter, a professor of environmental health and toxicology, director of the Institute for Health and Environment at the State University of New York, and one of the authors of the Science salmon study, put it this way in an interview posted on HealthDay's Web site: "Clean up the food you feed to the fish and the problem will go away."