Lice affect more salmon than thought, study says
By Judith Lavoie, Times Colonist, November 11, 2010
Sea lice from fish farms appear to have spread to wild salmon in a much wider area of coastal B.C. than previously believed, a newly published study concludes. However, the results have been dismissed by the B.C. Salmon Farmers Association as misleading and tenuous.
The peer-reviewed scientific paper by three researchers — Michael Price of Raincoast Conservation Foundation and the University of Victoria, Simon Fraser University professor John Reynolds and biologist Alexandra Morton — was published this week in the Canadian Journal of Fisheries and Aquatic Sciences.
“Our results [show] that salmon farms are a major source of sea lice on juvenile wild salmon in multiple salmon farming regions in B.C.,” said Price, the lead author.
Most previous studies concentrated on the Broughton Archipelago, but this study looks at wild fish in three salmon farming regions — the Broughton, Georgia Strait and Finlayson Arm on the Central Coast — comparing them with
fish around Bella Bella, where there are no fish farms.
Louse levels were highest near salmon farms and decreased with the number of farms, the researchers found.
“Everyone thought before it was a Broughton-specific problem and we are showing here that it is a problem in every region we investigated,” Price said.
The study found that about five per cent of young salmon not exposed to salmon farms were infested with sea lice, compared with between 30 and 40 per cent of juveniles in proximity to fish farms.
The highest infestations were found around the Discovery Islands, where the largest amount of farm salmon is produced, the study found.
“The Discovery Islands is a region of high conservation concern given that one-third of B.C.’s juvenile salmon migrate through the region en route to the open ocean,” Morton said.
“It includes Canada’s crown jewel of salmon systems — the Fraser River.”
Price said the “staggering levels” of sea lice found on pinks and chums around Georgia Strait could have implications for Fraser River sockeye.
In 2007, juvenile sockeye were schooling with lice-infested pinks and chums, and that run failed to return in 2009, Price said.
The findings underscore the importance of moving farms away from juvenile salmon migration routes or switching to closed-containment aquaculture, he said.
The study also raises questions about unstudied wild areas with farms, such as Clayoquot Sound and Nootka Sound, he said.
But Colleen Dane, Salmon Farmers Association spokesman, said the study should be read critically.
The paper looks only at the presence of salmon farms instead of differences such as salinity and temperature, she said.
“They are tenuous comparisons. Bella Bella has the lowest salinity of all the area, which makes it a questionable control site,” Dane said.
The paper refers to irrelevant data from Europe when genetic studies have shown a clear difference between Atlantic and Pacific sea lice, Dane said.
“There have been many studies looking at the effect of sea lice on wild fish which have found that Pacific salmon are not harmed by the naturally-occurring marine parasite that they have always lived with,” she said.
“The only salmon that could be threatened are the pinks at very early stages of life, which is why farms operate under strict management and treatment programs during the outmigration.”
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