Salmon, once a pricey delicacy, is now an affordable staple at supermarkets and sushi restaurants everywhere. For that, we can thank fish farms. They produce 70 percent of the salmon eaten by consumers, who savor its subtle texture and rich flavor. Medical researchers say the fatty acids in salmon might help prevent cancer and heart disease.
So it was troubling that researchers over the past few weeks may have found an infectious disease known as salmon anemia in wild fish in British Columbia. Lawmakers and fisheries managers in the U.S. and Canada see the illness as a threat to a $3 billion industry. Although Canadian officials said further tests seemed to be negative, the episode is a reminder of the need to make serious improvements in aquaculture practices.
The virus that causes the disease originated in the mid-1980s in Atlantic salmon fish farms in Norway and spread to Scotland, Canada and the U.S. Farms in Chile also were infected, probably via imported eggs.
A benign variant of the disorder existed in the wild, but it mutated in farms’ netted pens, where hundreds of thousands of fish can be held in water fouled by waste and unconsumed feed. Fish, much like domesticated animals on commercial farms, often are fed a diet laced with drugs to ward off bacteria, fungi and parasites that can result from overcrowding.
There is no cure for salmon anemia. Once it strikes, a farm’s entire stock usually must be destroyed. Often the farm has to be shut. Humans aren’t affected.
Just how much harm the disease caused to wild Atlantic salmon is hard to judge. Most of them had already been wiped out, long before the advent of aquaculture, by pollution, overfishing and dams that cut off their river spawning grounds. Pacific salmon, though more abundant, face the same threats.
Senators from Washington, Oregon and Alaska have taken the right step with a legislative amendment calling for a study of the possible impact the infection might have on the Northwest Pacific’s fishing industry. U.S. agencies, including the Department of Agriculture, along with Canadian and American Indian tribes, are developing plans to conduct more tests, trace the origin of the disease and begin developing ways to combat it.
Fighting salmon anemia shouldn’t require banning fish farms. The industry is indispensable, because the demand for seafood is driving wild stocks to the point of collapse. The United Nations Food and Agriculture Organization estimates that Atlantic populations of cod, haddock and flounder have declined by as much as 95 percent.
But reforms are needed. For one thing, governments should consider stricter guidelines on how many fish can be packed into netted pens. This would cut pollution and reduce the stress on fish that makes them susceptible to disease.
Farms also should be placed farther apart. One lesson from the outbreak of foot-and-mouth disease among livestock in the U.K. a decade ago was that when farms are dispersed, contagion is reduced.
And as in most fights against infectious disease, cleanliness helps. Norway, where salmon anemia first appeared, reduced its incidence by as much as 90 percent by aggressively decontaminating the equipment that’s used to contain and transport fish, and by treating effluent from fish-processing plants.
Norway also established harvest insurance programs, which gave fish farms the incentive to quickly destroy infected fish. If private insurers in Canada won’t offer adequate coverage, government guarantees might be needed as a backstop.
Finally, some fish farms, particularly in British Columbia, should be relocated away from the migratory corridors of wild fish, so that any anemia outbreak that might occur there would be less likely to spread.
Better still would be an increased industry effort to explore moving fish farms inland, where it can be easier to isolate and control pathogens. This wouldn’t be cheap, but it might prevent much of the potential environmental harm to coastal areas from overly intensive aquaculture.
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