Photo Credit: Amy Rhomer/UBC News

Atlantic Salmon Feedlots Brought Virus to BC Waters

Recent study shows that factory fish farms are the source

The salmon farming industry claimed the damaging PRV virus occurs naturally in BC waters. Now scientists have proven that floating fish factories are the culprit

Atlantic salmon fish farmers said it was natural to BC waters, but they were wrong.

The case for open-net pen salmon factory feedlots on our coast has gotten even weaker after the release of a recent study about Piscine orthoreovirus (PRV). The disease, associated with kidney and liver damage in Chinook salmon, is being transmitted between the open-net salmon feedlots and wild juvenile Chinook.

Just as Islanders have needed to wear masks to protect us from the spread of COVID, juvenile salmon swimming by feedlots as they migrate need a barrier to stop the spread of diseases like PRV.

The salmon farming industry has claimed that the damaging PRV virus occurs naturally in BC coastal waters for years. Now scientists have proven what critics of these floating fish factories have long feared.

A recent study confirms that feedlots are the source of the disease. “This study’s genome sequencing clearly indicates PRV is not native to B.C. waters—it originated in the Atlantic Ocean and has been spread around the world through salmon aquaculture,” said study co-author Dr. Gideon Mordecai, in a University of British Columbia press release.

Dr. Modecai added, “[t]hat salmon farms act as a source and amplifier of PRV transmission. Because separate lines of independent evidence all point to the same answer, we’re confident in our finding.”

By sequencing PRV genomes, researchers were able to track the history of this virus and its arrival in BC, which they estimated to be approximately 30 years ago. This suggests that the introduction of PRV to B.C. and infection of wild Pacific salmon is a relatively recent phenomenon that has increased with the growth of open-net Atlantic salmon feedlot farms in the province, according to the UBC press release.

The study shows how Atlantic salmon feedlot farms are introducing pathogens to BC waters at the same time as many wild Pacific salmon populations are experiencing critical declines. The analysis also indicates a growth in PRV infections over the past several decades.

Though PRV does not appear to kill wild Chinook directly, it can weaken them and hamper a fish’s ability to feed and avoid predators.

The genomics study, published May 26 in the journal Science Advances, was a collaboration between the University of BC and the Strategic Salmon Health Initiative, a partnership of Fisheries and Oceans Canada, Pacific Salmon Foundation, and Genome BC.

“Our study reaffirms that a more precautionary approach to managing salmon farming in BC is warranted,” said study co-author Dr. Andrew Bateman of the Pacific Salmon Foundation. “The PRV findings, in particular, support calls to transition from open-net salmon farming towards farming technology that doesn’t allow disease transfer between farmed and wild salmon, protecting BC’s wild Pacific salmon from serious risk in the process.”

To find out more, check out this video.