WASHINGTON - Farm-raised salmon are high enough in cancerous chemical agents that consumption should be limited to one or two eight-ounce portions a month, according to a study published Jan. 8 in the journal Science and immediately disputed by the Food and Drug Administration.
The FDA maintains that any long-term health threat from farm-raised salmon is offset by the heart-healthy benefits of fish.
The study, a two-year $2.4 million project of the Pew Charitable Trust, analyzed farm-raised salmon purchased in Europe, Canada, the United States and elsewhere. PCB and dioxin levels were found to be highest in the fish from Europe and eastern Canada. Fish from Denver and New Orleans farms showed the lowest contaminant levels. Fish from Seattle, perhaps the capital city of the Northwest's long association with salmon, fell between the extremes, but a state study released a week later found even higher contamination levels in wild Chinook salmon from Puget Sound. (The state agency that issued the latter study declined to issue portion-per-month guidelines, noting that it would instead advise consumers to cook salmon in such a way as to drain off the fat drippings and to avoid eating salmon skin. The fat and skin generally secrete the highest levels of contaminants in a fish, though they may be found in the rest of it as well.)
Farm salmon are raised in salt-water pens and fed with pellets that contain fish oil, a concentrate drawn from batches of small fish such as the anchovy. Because contaminants harbor in the fat of fish, the pellet production process concentrates the contaminants found in all the small fish into the fatty oil that propagates through the farmed fish as they feed. The fish-farming industry plans to reduce contaminants in the fish by introducing soy oil into the feed pellets in place of fish oil. As the FDA pointed out in its response to the study, contaminant levels in farm-raised salmon have fallen dramatically since the 1970s.
But for now, many Americans, including many American Indians, who have been urged to eat fish for health reasons are now being told not to eat farm-raised salmon for the same reason.
Charles Hudson, public affairs officer for Columbia River InterTribal Fish Commission (CRITFC), said that although some casinos in Indian country serve farm-raised fish when they could "rebuild our salmon economy" by buying from tribal fishermen, most tribes are against fish farming.
He drew careful distinctions between farm-raised salmon, which never enter the wild; and hatchery-reared salmon, which grow in captivity and get released into the wild. CRITFC refers to them as "managed salmon." They are kept in the safe environs of the hatchery early on, when young salmon are most endangered in the wild. Their experience in the hatchery is managed so as to acclimate them to certain conditions in the wild, increasing their competitiveness once they are released for their journey to the sea and back. Between the protected environs and the acclimation, salmon and trout survivability have increased in some tribal programs.
A further distinction can be drawn between hatchery-reared and wild-spawned salmon, Hudson added. "Tribes have been trying to close that gap? Tribes are really in the forefront of reforming hatcheries to be more in concert with nature - to mimic nature rather than mock it."
In the Pacific Northwest, Hudson said, the main concerns with farm-raised fish are that they escape their pens and compete with hatchery-reared and wild-spawned salmon for habitat; and that wherever they were farmed - once brought to market, they compete with tribal fishermen for market share.