A sockeye salmon sample from the Fraser river. (Photo: Jody Eriksson Raincoast Conservation Foundation)
New study links wild sea lice to salmon farms
Friday, February 11, 2011, 03:20 (GMT + 9)
The British Columbia Salmon Farmers Association (BCSFA) has stated that additional research into sea lice and its effect on wild salmon stocks is both important and necessary in response to the findings of a new study that ties salmon farms to wild salmon infected with sea lice.
A new study, “Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada’s West Coast,” published this week in the Public Library of Science ONE links sea lice on Fraser River Sockeye with salmon farms. The study was conducted by researchers from Raincoast Conservation Foundation, Watershed Watch Salmon Society and the Universities of Victoria and Simon Fraser.
The study genetically identified 30 different stocks of infected Fraser sockeye that swim past open net-pen salmon farms in the Strait of Georgia, such as the endangered Cultus Lake stock. The researchers determined that parasitism of Fraser sockeye increased strongly after the juvenile fish passed by fish farms, and that the same species of lice were present in large numbers on the farms.
Further, after swimming past salmon farms, the juvenile Fraser sockeye hosted an order of magnitude more sea lice than Skeena and Nass River sockeye that migrated along the north coast, which is free of farms.
|Sockeye sampling. (Photo: Stan Proboszcz Watershed Watch Salmon Society)
"The implications of these infections are not fully clear, but in addition to any direct physical and behavioural impacts on juvenile sockeye, sea lice may also serve as vectors of disease or indicators of other farm-origin pathogens" said Michael Price, lead author.
As well, the study recorded the highest lice levels on juvenile sockeye in the Georgia Strait near a farmed salmon processing plant, which intensifies existing concerns regarding the full potential consequences of the salmon farming sector on wild salmon in BC.
The aquaculture industry agrees with the researchers that more work is needed.
"Our farmers take very seriously the responsibility of managing sea lice on our fish to ensure they are not putting additional stress on wild salmon," said BCSFA Executive Director Mary Ellen Walling. "Both sea lice and the challenges faced by BC's wild salmon are complicated, multi-layered issues and there is more work to be done."
|Juvenile sockeye Okisollo. (Photo: Jody Eriksson Raincoast Conservation Foundation)
The new study notes the factors that remain unknown. These are that the impact of sea lice infestation is blurred and that there is still no explanation for the prominent differences in the types of louse observed on wild salmon.
"We think the genetics research here is interesting -- and will help provide a fulsome view for people looking at the survival of Fraser River Sockeye," said Walling. "But we agree with what the authors of this report say: there are still questions here and more answers will only help make the environment and our industry healthier."
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By Natalia Real