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article imageStudy clears farm salmon from causing decline of wild salmon

By Stephanie Dearing     Dec 14, 2010 in Food
A study headed up by a veterinary pathologist from the University of California Davis has cleared fish farms based in British Columbia of causing the decline of wild salmon populations through passing on sea lice.
The lead author of the study, veterinary pathologist Gary Marty, said "For anybody concerned about the effect of farm salmon on wild salmon, this is good news. Sea lice from fish farms have no significant effect on wild salmon population productivity."
A press release from the University said, “The study concludes that farm fish are indeed the main source of sea lice on the area's juvenile wild pink salmon, but it found no statistical correlation between lice levels on the farms and the lifetime survival of wild pink salmon populations.” The study is based on confidential information from the commercial salmon interests in the Broughton Archipelago area, said the University, along with government data.
The study has already created a lot of controversy in Canada, where biologists who have studied the issue for years noted the fact that data about sea lice associated with farmed salmon in British Columbia have not been shared with the public. Some salmon farms have made generic information available, while the industry overall has taken the position that such data is private. The government of British Columbia, which collects the data through the auspices of the Ministry of Agriculture and Lands, refuses to release the data it has on hand.
The study, titled Relationship of farm salmon, sea lice, and wild salmon population, analysed 10 to 20 years of data provided by fish farms, and also examined 60 years of data collected about pink salmon. While the authors looked for evidence that sea lice caused a collapse of the pink salmon run in 2002, they said “We show that the number of pink salmon returning to spawn in the fall predicts the number of female sea lice on farm fish the next spring, which, in turn, accounts for 98% of the annual variability in the prevalence of sea lice on outmigrating wild juvenile salmon. However, productivity of wild salmon is not negatively associated with either farm lice numbers or farm fish production, and all published field and laboratory data support the conclusion that something other than sea lice caused the population decline in 2002.”
The study was warmly embraced by the British Columbia Salmon Farmers Association. The head of the organization, Mary Ellen Walling, said in a press release, "This is an important addition to the expansive body of research on sea lice in BC. It really shows - based on more information than ever - that properly managed sea lice are not the concern."
Walling went on to say “This is the connecting piece - the document that looks at farmed fish and wild fish data and therefore tells the whole story rather than one-side of it. It really highlights what salmon farmers have been saying all along: that wild fish survival is a complicated issue with many factors to consider."
Biologist, Alexandra Morton, who has been fighting to protect British Columbia’s wild salmon populations for many years, disagreed. She criticised the research, telling the Times Colonist "They clumped eight rivers in the Broughton [Archipelago] together into one and looked at all the returns as if they were going to one river and that has given a blurred image.” Morton pointed out the latest study did not actually disprove salmon deaths are caused by sea lice. The study, on the other hand, says wild salmon pose a concern for salmon farmers in British Columbia, because the wild fish introduce the sea lice to the farmed salmon.
British Columbia’s salmon farmers have a history of refusing to ‘play ball,’ causing conservationists to chafe due to the lack of cooperation. For example, in 2007 the Globe & Mail reported a story about how BC’s farmed salmon industry refused to participate in provincially mandated research on sea lice and other issues related to wild and farmed salmon.
It was only the beginning of December when the Cohen Commission, appointed by the Harper government to look into last year’s collapse of the Chinook fishery, ordered fish farms to provide data on the health of their fish dating back to 2000. The order was applied to the British Columbia Salmon Farmers Association and 99 salmon farms.
While some groups seeking to conserve wild species of salmon say oil and gas industries are creating a threat to the populations of fish, others hold there is a strong relationship between farmed salmon, sea lice and the losses of salmon. Watershed Watch, for example, claim that salmon farms provide perfect breeding grounds for sea lice, which propagate wildly if allowed. When young salmon heading out to the ocean pass by the salmon farms, the theory goes, they become infested with sea lice, and many die as a result.
Watershed Watch and another study conducted by the University of Alberta found sea lice contributed to the widespread decline of the pink salmon run in 2002, and the BBC, reporting on the story, learned that where salmon farms have been established, similar problems have been reported.
A study done in Norway comparing sea lice infestations between populations of wild sea trout and arctic char exposed to salmon farms compared to those wild salmon with no exposure to farms showed a higher incidence of infestation in those salmon exposed to salmon farms.
The most recent research, published in 2009, showed a very strong relationship between farmed salmon and infestation of wild salmon which spawn near the farms with sea lice. The theory is that farmed salmon kept in net pens allow the free passage of the parasite between wild and farmed salmon.
University of California Davis, Wild-Salmon decline was not caused by sea lice from farm salmon -
Proceedings of the National Academy of Sciences of the United States of America (PNAS), Relationship of farm salmon, sea lice, and wild salmon populations -
The Globe & Mail, Sea lice data to be made public -
T.Buck Suzuki Environmental Foundation, Province still blocking sea lice and disease data release
British Columbia Salmon Farmers Association, Press release, New study disproves sea lice accusations in Broughton -
Globe & Mail, Sea Lice Salmon researchers need fish-farm input – now -
Watershed Watch, Sea Lice -
BBC, Farm sea lice plague wild salmon,
Salmon lice infection of wild sea trout and Arctic char in marine and freshwaters: the effects of salmon farms -
How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere -
More about Wild salmon, Alexandra morton, Sea lce, Farmed salmon, Pink salmon
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