Fisheries and Oceans Canada says that a virus found among farmed Atlantic salmon in the Discovery Islands “poses minimal risk” to Fraser River sockeye salmon, even though much uncertainty remains about the pathogen and how it spreads.
Members of an expert committee briefed reporters on Thursday about piscine orthoreovirus, or PRV. The pathogen made headlines earlier this week when a Federal Court judge overturned a Fisheries and Oceans Canada (DFO) policy allowing young salmon to enter open-net pens without first being screened for the virus.
But scientists on Thursday’s conference call described the risks posed by PRV to Fraser River sockeye as very low.
“There is currently no evidence to suggest that PRV-1 causes disease and mortality in sockeye salmon,” said Gilles Olivier, one of the co-chairs of the peer-review committee.
PRV comes from Norway, and has caused disease there for a number of years, but the virus in B.C. has “lower genetic variability” and is less harmful in B.C.’s farmed Atlantic salmon, he said.
“It doesn’t seem to have the same effect in our Atlantic salmon here in B.C., on the West Coast, (as) it does in Norway,” said Olivier, a former DFO aquatic health official who is now retired.
Research shows that even high viral loads of the B.C. strain of PRV in juvenile Atlantic and sockeye salmon don’t cause mortality, he said.
Data from the review also shows the virus is highly prevalent among Atlantic salmon in net-pen farms and among chinook salmon throughout the Pacific Northwest.
“It has a wide geographic distribution among wild Pacific salmon in B.C., Alaska and Washington, but a lower prevalence than (among) farmed salmon,” Olivier said.
He said virus can’t be cultured, meaning scientists rely on special molecular tools and methods to detect it.
“It’s not easy to work with this virus,” he said.
Much remains unknown about how the virus behaves in B.C. coastal waters, said Dr. Craig Stephen, another co-chair of the review committee.
A high level of uncertainty remains due to “data gaps around things like what’s the concentration of the virus in the water… how well does the virus survive,” he said. “The usual exposure models couldn’t be done.”
Stephen is CEO of the Canadian Wildlife Health Cooperative and a professor at the Western College of Veterinary Medicine.
The 33-person peer-review committee included 15 participants from DFO. Other members came from environmental and Indigenous groups, academia and the aquaculture industry, along with other government departments, according to a DFO news release.
The committee met for three days in Vancouver last month to review evidence related to the spread of PRV from farmed Atlantic salmon in the Discovery Islands to Fraser River sockeye, said Jay Parsons, a senior DFO official.
No data from the review process was released to reporters. DFO said that “a full report on the peer-review findings” will be published on the Canadian Science Advisory Secretariat’s website in late spring, following a final review by committee members.
The PRV review was the sixth in a series of 10 risk assessments about the spread of pathogens from farmed salmon in the Discovery Islands area, Parsons said.
The risk assessments are part of a response to a federal inquiry into declining stocks of Fraser River sockeye salmon led by commissioner Bruce Cohen. The Cohen Commission’s report was released in 2012.
Last year, a DFO-led study found that that PRV causes the cells of wild chinook salmon to burst, leading to “liver and kidney damage, anemia and death,” according to Ecojustice, an environmental law charity.
On Monday, the Federal Court of Canada overturned a policy allowing young salmon to be transferred into ocean-based fish farms without first being screened for the virus. This followed lawsuits by ‘Namgis First Nation and by biologist Alexandra Morton, an outspoken critic of open-net fish farms.
Justice Cecily Strickland found that DFO’s threshold for acceptable harm to wild salmon was too high and that its policy didn’t comply with the precautionary principle. The court also found that DFO breached its duty to consult ‘Namgis First Nation about PRV.
Strickland gave the federal government four months to review the policy. DFO declined to comment about its plans during Thursday’s conference call.