Quirks & Quarks

Salmon CSI — A virus in BC's wild salmon came from salmon farms, research suggests

Scientists used genetic tools to map out a viral family tree to track it to its source, which they say was likely eggs imported for aquaculture from Norway.

Scientists used genetic tools to map out a viral family tree to track it to its source.

Researcher dissecting wild Pacific salmon tissues for molecular analysis and viral genomic sequencing. (Amy Romer)

When a scientist using genetic tools mapped out the family tree of a debilitating salmon virus, he discovered evidence that it was introduced to the B.C. marine environment by salmon aquaculture.

The piscine orthoreovirus, or PRV, was thought to be native to B.C. waters and therefore something wild salmon were used to living with.

PRV causes heart disease in Atlantic salmon. It appears to cause a different disease in wild Chinook salmon, called "jaundice anemia," with sub-lethal effects that can weaken the fish, potentially making it less able to deal with the stresses of the wild.

Acting on a bit of data and a hunch, Gideon Mordecai — a viral ecologist postdoctoral fellow at the University of British Columbia in the Department of Medicine — decided to track the spread of this virus in B.C. waters to its source.

He traced the virus back to the North Atlantic Ocean in Norway, in a genetic "bottleneck introduction event" about 30 years ago, which is consistent with the timing of Atlantic egg imports from Europe for Pacific salmon farms. 

The B.C. Salmon Farmers' Association told the Canadian Press it will review the findings, but said a tissue sample from 1977 suggests the virus was in B.C. waters before the salmon farms.

You can hear an interview with Gideon Mordecai by clicking the link above. 

Produced by Sonya Buyting and Jim Lebans. Written by Sonya Buyting.

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