Something's Fishy About Salmon Farming

A recent disease outbreak affecting salmon raises several questions about the industry behind your favorite fish dish. A new Bloomberg column lays out the issue:

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 United States. 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.