Four scientists share view sea lice didn’t cause collapse of sockeye salmon stocks

Mark Hume   Globe and Mail

 Sept 07, 2011

 A panel of scientists that was often at odds has told the Cohen Commission that sea lice can’t be fingered as the cause of the decline of sockeye salmon stocks, but the parasite may be a contributing factor.

Simon Jones, a research scientist with the Department of Fisheries and Oceans, and Sonja Saksida, executive director of the Centre for Aquatic Health Sciences, told the federal commission that they don’t think sea lice are having a major, direct impact on sockeye populations, or that salmon farms are the cause of lice infestations in wild stocks.

All four witnesses replied in the negative when asked if sea lice “acting in isolation” could have caused the collapse of sockeye salmon stocks.

“No … but nor do I believe sea lice do act in isolation,” said Mr. Price, expressing the view that lice are part of a complex and still emerging picture.

While all four were sworn in as expert witnesses on the subject of sea lice, their diverging views on the topic underscored one of the main difficulties Mr. Justice Bruce Cohen of the B.C. Supreme Court is facing in his inquiry. Science is not certain on many of the topics that have come under scrutiny, because so little is known about what happens to salmon in their early life stages.

“There is this big black hole … you don’t know what happens to fish when they leave freshwater,” said Dr. Saksida, who suggested water temperatures, salinity and the abundance of food may be more important factors than sea lice.

Dr. Jones told the commission the science on sea lice in the Pacific is still relatively new, and that’s why the picture remains so murky. He said studies in Europe and on Canada’s East Coast are of limited help, because the sea lice found in the Pacific are genetically different from those in the Atlantic.

“The science of sea lice in British Columbia is still in its infancy,” he said, noting that studies of B.C. sea lice date back only to 2002. “There is still an awful lot we have to learn.”

But Mr. Price and Dr. Orr said studies they have been involved with make it clear that wild salmon are being infested with sea lice that originate in salmon farms.

Mr. Price said by looking at young salmon before and after they swam past salmon farms, they were able to confirm that lice infestations intensified in wild salmon stocks, after they encountered farms…

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