Ottawa, March 2, 2004 Salmon farms in British Columbia may pose a threat to wild salmon stocks, a paper published today in the Canadian Journal of Fisheries and Aquatic Sciences claims. The paper presents evidence that native fish sampled near the farms are more heavily infected with parasitic sea lice. Lead author Alexandra Morton, a registered professional biologist and private researcher, believes the parasites multiply on the farms and are then transmitted to juvenile native salmon, causing recent drastic declines in wild fish populations. "If we don't do anything, we're definitely going to lose the wild salmon," said Morton.
Morton monitored the levels of infection of sea lice (unrelated to human lice), naturally occurring parasites that infect salmon only, on juvenile pink and chum salmon in British Columbia's Broughton Archipelago, a chain of islands between the mainland coast and the northern end of Vancouver Island. She then compared infection rates on salmon from sites near to and far from the farms.
"We found 3 cases of sea lice in a sample of 1,018 juvenile salmon outside of the Broughton Archipelago. Within the Broughton Archipelago," where there are 28 Atlantic salmon farms, "we found 4,338 of this species of sea louse on 1,138 salmon," -- a 1,000-fold difference, said Morton. Her study showed potentially lethal levels of infection in 90 percent of wild juvenile salmon. Morton believes the young native salmon become infected when they swim near the farms during their migration from freshwater streams to the open ocean.
Morton said that to preserve native salmon stocks, "the farm fish have to be separated from the wild fish. There are alternative technologies that allow farmers to grow fish in facilities that provide a barrier to the marine environment." A barrier would prevent transfer of disease
Contact: Alexandra Morton
National Research Council of Canada