Atlantic salmon and trout raised in federal hatcheries in the Northeast have high enough levels of dioxin and other pollutants that anglers should eat no more than half a serving a month, federal officials said Thursday.
The U.S. Fish and Wildlife Service commissioned the tests to determine whether they were picking up PCBs and other contaminants from feed.
A study published in January in the journal Science had suggested pollutants found in farm-raised salmon came from PCBs, or polychlorinated biphenyls, in the fish oil and meal fed to the fish.
Each year, the agency's northeast regional office provides about 14,000 Atlantic salmon, lake trout and rainbow trout that are no longer used for breeding to eastern states for release in their waterways. The big fish are prized by anglers.
The contaminant levels were below both the safety mark set by the Food and Drug Administration for commercial sale, and by the federal Environmental Protection Agency for consumption of fish taken by recreational anglers.
However, tests at five hatcheries showed the levels of PCBs and dioxins in the salmon and both species of trout were high enough for the EPA to urge anglers to eat no more than half a serving a month.
"Based on the test results, we will provide the hatchery fish to states that request them for their recreational fisheries," Marvin Moriarty, regional director, said Thursday. "But we are recommending that state fish and wildlife directors discuss the test results with their public health officials."
State health agencies can adopt the EPA advisories or set their own levels.
Moriarty also said the service was working with its fish food suppliers to try to eliminate the contaminants and investigate other possible sources of contamination.
Dan Kuzmeskus, who supervises the service's hatcheries in the 13-state region stretching from Maine to Virginia, said officials had not yet heard from any of the states as to whether they will still take the fish.
The tested fish had been held from two to eight years and included Atlantic salmon from the agency's hatcheries in Vermont and New Hampshire, lake trout from a hatchery in Warren, Pa., and rainbow trout from a hatchery in White Sulphur Springs, W. Va.
The effect would be less on stocking programs because those fish are held a shorter time, he said.
Still, Kuzmeskus said the highest levels of PCBs found during the study were from four-year-old Atlantic salmon captured when they returned to the Merrimack River. The salmon hadn't been fed at the hatchery following their capture _ so they would have picked up the PCBs from prey in the ocean.
"We can't draw any conclusions from that," Kuzmeskus said, "but it does suggest that we need to go out and take a closer look at our populations of sea-run salmon in other rivers."