Lice from fish farms threaten Canadian wild salmon
By Julie Steenhuysen
CHICAGO (Reuters) - Infestations of sea lice at salmon farms on Canada's west coast are threatening local wild pink salmon populations and could result in their extinction in another four years, Canadian researchers said on Thursday.
They collected nearly four decades of data on the numbers of pink salmon in rivers along the central coast of British Columbia, comparing wild salmon populations exposed to salmon farms to those not exposed.
"The results are striking. Overall the populations that were not exposed to sea lice disease are stable or increasing," said Martin Krkosek, a fisheries ecologist from the University of Alberta in Edmonton, whose study appears in the journal Science.
"This is true even for populations with commercial fishing," Krkosek told reporters in a telephone briefing.
"Overall, populations that were exposed to sea lice-diseased salmon farms are depressed and are declining quickly. This was true even though commercial fishing was closed on these populations," he said.
The researchers believe their findings have implications beyond the region and fish populations they studied. They said their findings indicate that in certain situations fish farms can threaten wild fish populations by concentrating and spreading infectious diseases.
Sea lice are parasites that attach themselves to the skin of wild salmon in the open ocean, feeding on their skin and muscle tissue. Adult salmon can survive a small infestation, but juvenile salmon headed from the river to the sea are too vulnerable to withstand an infestation.
"While sea lice are natural, there are mechanisms in place to ensure they don't kill their host," Krkosek said. Continued...