Time to end BC sea lice debate
Unlike operators in other regions, salmon farmers in British Columbia have never considered the impact of sea lice on their fish a serious threat. Historically, the occasional treatment was deemed necessary when millions of wild salmon came in from the open sea to migrate past the farms on their way to freshwater spawning grounds, often carrying large numbers of naturally - and historically documented - sea lice that would shed eggs that hatched and made their way into the salmon farms. Some farmers were even known to put bags of onions inside the pens in order to discourage the presence of the parasites- an early “organic” method of sea lice treatment as opposed to using chemical methods.
Today, salmon farmers in BC are forced by regulation to treat their fish long before sea lice numbers have reached levels that could potentially represent a threat to the wellbeing of the salmon in their pens, and at levels that are typically much lower than those found on naturally migrating "wild" salmon, many of which originate in man-made hatcheries and other artificial facilities.
An article in yesterday’s Business in Vancouver makes the common error of referring to the wellknown anti-salmon farming activist Alexandra Morton as a “biologist”, despite her total lack of any scientific or educational credential that would justify such a title. The article suggests that (her) “Sea lice theory (is) questioned in wake of 2014 salmon run”:
More than a decade ago, when scientists were trying to figure out why some pink salmon runs were on the verge of collapse on the B.C. coast, a biologist studying orca whales in the Broughton Archipelago stumbled on what she thought might be the culprit. Alexandra Morton found juvenile pink salmon in the Broughton Archipelago were infected with sea lice. Because the schools of wild pink salmon swim past open-net fish farms as they migrate out to sea, she theorized that sea lice – and possibly other diseases – from farmed salmon could be destroying wild pink salmon stocks.
When only 1.4 million Fraser River sockeye returned in 2009, sea lice from salmon farms again became a prime suspect. In 2010, the Cohen Commission gave the theory serious consideration: 11 of its 75 recommendations related to fish farm management. But since the 2009 crash, both Fraser River sockeye and pink salmon stocks have come back gangbusters. This year’s Fraser River sockeye return was estimated last week to be 20.8 million – a massive return, though seven million short of 2010, which was a record year.
Carl Walters, professor emeritus for the University of British Columbia Fisheries Centre, believes the recent robust returns of sockeye and pink salmon should put the sea lice theory to rest. “All the dire predictions about fish farms and diseases and the correlation that people found between the buildup of fish farming and the decline of the salmon has broken down,” Walters said.
Don Noakes, former head of the Fisheries Department’s Pacific Biological Station, current dean of science and technology at Vancouver Island University and one of the experts called on by the Cohen Commission, said most “good scientists” never did give much weight to the sea lice theory. “I don’t know that it puts the sea lice issue to rest or not,” Noakes said, “but certainly there’s no evidence to support sea lice being any significant factor in the production of Fraser sockeye.”
Morton said that far from disproving the sea lice theory, rebounding wild salmon stocks can be credited to the changes to aquaculture practices that her research helped promote. Whereas aquaculture companies used chemicals like Slice to treat farmed salmon only when they were infected, Morton said they now use it prophylactically to control the spread of lice in advance of out-migrations of juvenile pink salmon. The result, she said, is that the average infection rate in juvenile salmon in the Broughton Archipelago has dropped from nine lice per fish to one or fewer.
