Could Canadian Fish Farms Harm California's Wild Salmon?

Dead salmon in the Fraser River | Photo: Sam Chua/Flickr/Creative Commons License

For the last few years, British Columbia has been the site of swirling controversy as biologists charge that salmon farms may be spreading exotic diseases to the province's formerly numerous wild Pacific salmon runs.

An independent documentary from last year suggested that farmed salmon from the B.C. coast may pose a threat to wild salmon runs in other places, as the viruses that afflict the farmed salmon may survive the journey from fish farm to grocery store to your kitchen sink. The viruses are not considered a threat to human health, but can wipe out wild Pacific salmon stocks. California salmon may also be at risk when they mingle with Canadian wild salmon in the North Pacific.

The actual level of risk to other runs of wild salmon is unknown, say activists, in part because Canadian officials are obstructing independent scientific investigation of the health of fish in the hundreds of salmon farms in British Columbia. But it's possible that the viruses now afflicting British Columbia's farmed salmon could be spread to California's wild runs through acts as simple as washing salmon steaks in a kitchen sink prior to cooking.

According to the documentary, "Salmon Confidential," government agencies in Canada have allowed hundreds of penned farms for exotic Atlantic salmon to be built along the Johnstone Strait, a narrow passageway between Vancouver Island and the mainland through which the vast majority of the Fraser River's native wild salmon swim on their way to their spawning grounds.

In those fish farm pens, thousands of imported Atlantic salmon are kept in close quarters and fed artificial food, then harvested for the export market. The overcrowding allows parasites and pathogens to spread rapidly through the pens. And though the Atlantic salmon can't get out of the pens, their waste can, filling the Strait with effluent.

As shown in the film, biologist Alexandra Morton and others contend that by forcing B.C.'s wild salmon to run a gauntlet of fish farms and their effluent on their way to their Fraser River spawning grounds, the fish farms may essentially be infecting the Fraser's wild salmon populations, including sockeye and coho, with some of the most deadly diseases salmon suffer. As a result, say activists, the Fraser's salmon runs have crashed catastrophically, with between 10 and 13 million fish missing in the 2009 runs alone.

Here's the trailer (the full movie can be viewed online):

Among the ailments found in wild salmon that swim near the Johnstone Strait salmon feedlots are the viral diseases Infectious Salmon Anemia (ISA), a highly lethal pathogen often called "salmon flu"; Salmon Alphavirus, which causes pancreatitis; Salmon Leukemia; and Piscine Reovirus, a newly discovered virus linked to a condition called Heart and Skeletal Muscle Inflammation, in which muscles -- including the heart -- lose their tone.

All of the viral diseases can kill wild salmon, and some have been fingered as likely culprits in mass die-offs of Fraser River salmon before the fish can spawn.

U.S. law forbids the importation of salmon infected with ISA, and several fish farms on Canada's Atlantic coast have been affected by the ban. But as the Canadian government has yet to confirm the presence of ISA in Johnstone Strait fish farms, that farmed Atlantic salmon is still being imported by the United States.

The viruses can remain viable even after freezing, and could conceivably enter the water supply of local salmon streams when purchased fish is washed before cooking. Though the majority of wastewater in California is run through sewage treatment plants before discharge into the state's coasts and rivers, such plants are not always very effective at removing viruses from their treated wastewater. ISA causes infected fish to produce virus-laden mucus, which can remain on whole frozen fish and which would almost certainly be rinsed down the drain by meticulous cooks.

Though the movements of salmon during their oceangoing periods are somewhat of a mystery, it's also very likely that salmon that spawn in California rivers intermingle with Fraser River salmon while at sea. Though most salmon do return to their natal spawning rivers, some do end up in the wrong place and can thus offer yet another way for a virus to spread to previously uninfected streams.

It's unlikely that either a small amount of virus load in urban wastewater or chance encounters with oceangoing salmon from Canada will be quite as effective a vector for viral diseases as forcing millions of Fraser River salmon to swim past hundreds of fish farms. But unlike the healthier runs of the Canadian Pacific coast, California's salmon runs are already teetering on the brink. Even a less effective way of spreading disease could prove catastrophic.

It also seems unlikely that Californians worried about the health of their native salmon runs will get any hard data from the Canadian government anytime soon. On Friday, Canada and Mexico joined forces to block an inquiry under the North American Free Trade Agreement into whether Canada was failing to enforce its environmental laws by letting wild salmon be exposed to parasites and pathogens emitted by fish farms.

The petition to NAFTA's Commission for Environmental Cooperation, a dispute resolution body, was filed in February 2012 by the Center for Biological Diversity, the Pacific
Coast Wild Salmon Society, the Kwikwasu'tinuxw Haxwa'mis First Nation, and the Pacific
Coast Federation of Fishermen's Associations. The groups had asked for a fact-finding inquiry into whether Canada was failing to enforce its Fisheries Act by protecting British Columbia's wild salmon.

"This NAFTA process is supposed to shine light on whether environmental laws are being enforced, but the process has become increasingly politicized and it's clear Canada does not want the facts revealed about the damage to wild salmon from industrial fish farms," said Jeff Miller with the Center for Biological Diversity.

Until we get some straight answers out of Canada -- if we ever do -- it's just one more good reason to buy only wild-caught salmon.