Pollutants Spread by Salmon
Wide-traveling fish may bring DDT and other pollutants into pristine waters.
Ever since persistant organic pollutants such as PCBs and DDT began showing up in animals and people inhabiting Arctic ecosystems, scientists have assumed all the contaminants have arrived by air. Now it turns out some of the chemicals also are carried into the otherwise pristine areas by migrating fish.
A recent study in Alaska by biologist Goran Ewald of Lund University in Sweden found that grayling in a lake used by spawning salmon carried more than twice the concentration of organic pollutants than grayling in a nearby lake with no migrant visitors.
The salmon had spent as many as three years traveling 255 miles into the Gulf of Alaska and beyond, gradually accumulating pollution in their fat. As the fish burned up fat reserves to make the arduous return trip, the toxics became more concentrated. And when the grayling ate the salmon carcasses and roe, they in turn became contaminated. The finding strongly indicates that the chemicals transported to the area by the salmon move from the migrants throughout the ecosystem´s food chain.