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Disease Found in Wild Salmon

Are farmed salmon the source of a viral infection off the coast of British Columbia?

A male Atlantic salmon. Image courtesy of Flickr user U. S. Fish and Wildlife Service - Northeast Region

Salmon farming has received its share of criticism for being detrimental to the environment. Many salmon are raised in net pens, which allow fish waste, chemicals and farming byproducts to spread into the wild. There’s also the threat of pathogens that could thrive in crowded pens and escape to harm natural fish populations. One disease, infectious salmon anemia, was once thought to be a problem exclusive to farmed Atlantic salmon. A new study by a group of researchers from Simon Fraser University in British Columbia has found that this influenza-like virus is infecting naturally ocurring salmon populations.

Infectious salmon anemia was first observed 1984 and occurs most often in overcrowded, filthy salmon pens. As the name suggests, the virus causes anemia, the condition in which a body doesn’t have enough healthy red blood cells to deliver oxygen to its tissues. Infected fish may exhibit symptoms—such as pale gills and loss of appetite—or they may outwardly seem perfectly fine. While the disease doesn’t pose any risks to humans, it can wipe out upwards of 70 percent of a farmed salmon population.

This is the first time the disease has been found in wild fish off the coast of North America. After observing a decline in the salmon population off the British Columbia coast, researchers collected 48 specimens for study and discovering two juvenile fish infected with the disease. While there is currently no evidence to definitively link fish farming to the presence of salmon anemia in wild populations, there could be devastating ramifications, not just for the fishing industry, but for the wildlife that depends on salmon for food. “It’s a disease emergency,” James Winton, director of the U.S. Geological Survey’s fish health section, told the Associated Press. “We’re concerned. Should it be introduced, it might be able to adapt to Pacific salmon.”

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