Sea lice infestation could kill up to ‘millions’ of wild salmon

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Independent researcher Alexandra Morton claims a sea-lice infestation in the Broughton Archipelago will kill "hundreds of thousands if not millions" of wild salmon this spring.

And the controversial biologist, who in 2001 sounded the alarm about sea-lice infestations on the B.C. coast, is once again blaming fish farms for the outbreak, saying densely packed farm pens serve as reservoirs for the lice, which drift with the tide, infecting passing wild salmon.

The BC Salmon Farmers Association says the charge is without scientific merit, because there has been no outbreak of lice in farms and when lice are detected, fish are promptly treated with SLICE, a pesticide that is 95 per cent effective.

But Ms. Morton says she has been collecting samples of young pink and chum salmon at the same three sites near salmon farms in the Broughton Archipelago each spring since 2001, and is now seeing some of the highest numbers of sea lice.

"I've had a crew out there since April 4 and we were very surprised to see heavy concentrations of sea lice," she said Wednesday. "We look at 100 fish at each site, so 50 pink and 50 chum and … 94 per cent are infected."

Ms. Morton said the sample sites are all in the vicinity of fish farms and the tiny, juvenile wild salmon, which recently hatched from eggs in nearby rivers, average two lice a fish, which is enough to kill them at this early stage of life.

A flurry of scientific research into lice was done following the collapse of pink salmon runs in the Broughton Archipelago after Ms. Morton warned a heavy infestation was going to decimate stocks.

The federal government, the fish farming industry and non-governmental organizations then agreed on practices to better control sea lice in farms. Some farms were fallowed when juvenile salmon were migrating past, and farmers began more rigorously treating infected fish.

Ms. Morton said those methods seemed to work for a period.

"For the past seven years we saw excellent low levels of lice. Suddenly, this year, we are back up," she said. "Now, we don't know whether the salmon farms failed to treat, or if their treatment failed."

Jeremy Dunn, a spokesman for the BC Salmon Farmers Association, said sea-lice levels are currently low on farmed fish, however, and when a problem has been encountered, the fish have been treated.

Mr. Dunn said since 2010, under the Broughton Archipelago Management Plan, fish farms carefully monitor and control sea lice, including treating farms for lice in the weeks before juvenile wild salmon migrate past.

He said the high numbers Ms. Morton is reporting are likely due to natural conditions, including high ocean salinity levels, warmer water temperatures and large spawning runs of adult wild pink and sockeye salmon that brought lice to the area last fall.

Sean Godwin, a Simon Fraser University doctoral biology student, published a paper last week that showed wild juvenile sockeye salmon infected with sea lice have a tougher time surviving.

"We found sockeye salmon highly infected with sea lice are less able to compete for food than lightly infected or uninfected fish," said Mr. Godwin, whose study showed heavily infected fish were able to consume about 20 per cent less food on average.

Mr. Godwin said his research did not try to determine the source of the lice he found on wild sockeye, but he noted that a past study has shown salmon farms do spread sea lice to wild stocks.

In a statement, Chief Bob Chamberlin, chair of the First Nations Wild Salmon Alliance, said he was "deeply concerned" by reports of sea-lice infestations in the Broughton Archipelago, near Port McNeill on northeast Vancouver Island. He called for an end to the expansion of fish farms on the B.C. coast.