Virus killing farmed Pacific and Atlantic salmon raises risk for wild B.C. population: study
Scientists have discovered that a highly-contagious virus impacting farmed Atlantic salmon also harms their Pacific cousins, and could pose a serious threat to British Columbia’s declining wild salmon population if it spreads from ocean pens to key migration routes.
The study, which will be published in the journal FACETS later this month, was done in partnership with the Pacific Salmon Foundation and Genome BC. Researchers looked at samples of farmed Pacific Chinook and Atlantic salmon, and confirmed the presence of the highly-contagious piscine reovirus (PRV) in both species.
“It’s the same strain of virus,” lead author Kristi Miller, the head of salmon genetics for Fisheries and Oceans Canada, told CTV News.
In Chinook salmon, the fish developed jaundice anemia. It’s a condition marked by the fish’s yellowish colour and organ failure. In Atlantic salmon, the virus can cause heart and skeletal muscle inflammation, or HSMI.
Researchers have linked the PRV strain to a surge of related disease outbreaks reported in Pacific salmon in Norway, Chile, Japan and Canada in recent years.
But Shawn Hall, a spokesperson for the BC Salmon Farmers Association, said the latest study needs to be “looked at with a critical eye.”
“Its conclusions are speculative at best,” he said, adding that the findings are “inconsistent” with those of other scientists around the world or what fish farmers see every day.
Hall pointed to previous research summarized in a report on the Fisheries and Oceans Canada website, which found that, unlike in Norway, “experimental exposures” of the B.C. strain of PRV to Pacific and Atlantic salmon in the province did not result in disease or death among the fish.
“This suggests PRV in B.C. has a low ability to cause disease (low virulence) for these species,” the report said.
Another report recently produced by the BC Salmon Farmers Association following a workshop with scientists to discuss the PRV issue said that, to date, HSMI has only been "described in farmed fish, globally (never diagnosed in wild fish)."
Hall said the fish on B.C. farms are “generally very healthy” and the association continues to participate in research on health of both wild and farmed salmon.
PRV is less of a problem inside B.C. fish farms, where feed can be medicated. In most cases, impacted fish are still fit to be sold and eaten by humans. The greater risk lies in the possibility of farmed adult fish infected with the disease spreading it through the water as wild juvenile salmon migrate past open nets.
“If the farmers say it doesn’t affect their bottom line, that is fine for them,” Miller said. “But we have something else at stake here. We have risk to the wild salmon.”
Washington state is set to phase out marine farming of Atlantic salmon and other non-native fish by 2022, under legislation signed by Gov. Jay Inslee.
The move follows the escape of up to 263,000 invasive Atlantic salmon into Puget Sound in late August, after net pens belonging to Canada’s Cooke Aquaculture Pacific collapsed.
“Escaped farmed salmon, which are most often infected with PRV, could also be a transmission vector for freshwater infections in wild fish if they enter rivers,” Miller wrote in the study.
Many wild salmon advocates in B.C. argue the province should follow suit with a similar plan to reduce risk. Fisheries and Oceans Canada’s 2018 Pacific salmon outlook suggests the decline in overall population will continue.
While most of the backlash against B.C.’s salmon farming industry has been directed at fish farms, there are also growing concerns that processing plants may be contributing to problems with disease.
Last November, CTV News obtained video footage that shows a farmed-salmon processing plant in the Discovery Passage channel off Vancouver Island discharging bloody effluent from a pipe under the water. The pipe is connected to Brown's Bay Packing Co., a farmed Atlantic salmon processing plant near Campbell River, B.C. Water samples sent to the Atlantic Veterinary College for analysis revealed the presence of PRV.
A report tabled in Parliament by Commissioner of the Environment and Sustainable Development Julie Gelfand on April 24 suggests the Department of Fisheries and Oceans is not adequately managing the risks associated with the growing salmon farming industry.
The report highlights lax enforcement of current regulations, as well as the absence of requirements to monitor the ocean floor beneath fish farms, and clear national standards for nets and equipment.
Gelfand’s report also found that only one of the 10 risk assessments of key diseases the Department of Fisheries and Oceans had committed to completing by 2020 has been done.
“We found that the Department was not monitoring wild fish health,” the commissioner wrote in her report.
Jay Ritchlin, the David Suzuki Foundation’s director general in Western Canada, worries that farms in waters where juvenile wild salmon grow up are prematurely exposing those populations to adult diseases.
“Diseases and parasites that might be considered somewhat natural in an adult population are being put in front of juvenile wild salmon in a way that never happened in evolution,” he said. “Given the numerous challenges that wild salmon face, every exposure to increased disease risk is a problem, and one we should try to mitigate.”
Ritchlin is among the growing chorus of observers calling for the industry to shift to contained farms, ideally on land, both to control farmed fish losses and prevent the spread of disease into the natural ecosystem.
He said the lives of B.C.’s wild salmon population likely hang in the balance.
“If these diseases get into the wild population we will likely never see those fish again. They will end up on the bottom of the ocean or in the belly of a seal, and they will lose out because they are not as fit as other wild fish,” he said. “They don’t have veterinarians.”
With a report from CTV’s B.C. Bureau Chief Melanie Nagy