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Chinook salmon. (Photo: NOAA)
Atlantic salmon virus could also affect chinook salmon
CANADA
Tuesday, May 08, 2018, 22:20 (GMT + 9)
A new scientific study states that the same virus causing disease in farmed Atlantic salmon is likely to make chinook salmon sick, which has led to some scientists and environmentalists to call on fish farmers and Fisheries and Oceans Canada (DFO) to help stop the spread.
The study, which is part of the strategic salmon health initiative (SSHI) – a partnership of the Pacific Salmon Foundation, Genome BC and DFO -- suggests that the strain of Piscine orthoreovirus (PRV) that causes heart and skeletal muscle inflammation disease (HSMI) in Atlantic salmon is likely to cause disease in chinook salmon in British Columbia.
“These findings add to the existing concerns about the potential impacts of open net salmon farming on wild Pacific salmon off the coast of BC,” pointed out Dr. Brian Riddell, president and CEO of the Pacific Salmon Foundation.
HSMI is a significant cause of mortality and economic loss in the salmon-farming industry and has to date been reported in Norway, UK/Scotland, Chile and British Columbia.
Divergent strains of PRV have been associated with jaundice-related diseases in Pacific salmon species in Japan, Norway and Chile, but until now the PRV-1 strain that causes HSMI, and the only strain detected in BC, has not been shown directly affiliated with disease in Pacific salmon.
“Our study used novel molecular tools to show that PRV-1 was intimately involved in the development of jaundice/anemia in chinook salmon,” said Dr. Kristi Miller-Saunders, Fisheries and Oceans Canada and lead scientist in the SSHI.
“The study also reveals a difference in PRV-1 sensitivity between species that could easily explain why the virus causes inflammation in Atlantic salmon and cell death in chinook salmon,” Riddell stressed.
Nevertheless, Michelle Rainer from the department of fisheries and oceans said there have been no documented cases of jaundice in wild Pacific salmon to date.
“DFO will continue to monitor the health of wild salmon populations in Canada and seek to clarify if wild Pacific salmon are susceptible to jaundice/anemia disease,” she said.
In addition, BC salmon farmers say their fish are not to blame.
“The presence of a virus does not necessarily equate to the presence of disease,” said Shawn Hall, spokesperson for the B.C. Salmon Farmers Association.
Although rates of PRV in farmed salmon are high, Hall said, farmers report their fish are generally healthy, not having developed heart and skeletal muscle inflammation disease in as great numbers.
“The report’s findings are just not supported by what we see on the farms where we care for fish every day,” Hall said.
But Riddell said that misses the point of the study. “It’s not about the mortality in the farm — it’s about the risk to the passing fish,” he said.
For his part, Stan Proboszcz, science and campaign adviser for the environmental group Watershed Watch, pointed out there are differences between the lives of, and risks faced by, farmed and wild salmon, The Star Vancouver reported
“Wild salmon have a rough life out there — they’re being chased by orcas,” Proboszcz said, adding that chinook salmon are a primary food source for whales. “It may be that some of the farmed fish don’t get sick. But also maybe they’re not as stressed,” he said.
Meanwhile, Dr. Ian Gardner, Canada Excellence Research Chair in Aquatic Epidemiology, called the study both “interesting” and “limited.”
The samples used for the study, he said, give scientists a “snapshot in time,” making it difficult to conclusively prove that the Chinook salmon’s illnesses were caused by the PRV-1 virus.
“Working out whether it’s the virus alone or whether it’s virus and other factors is an important question,” Gardner said.
In Riddell’s view, the study goes far enough to encourage regulators to act on protecting wild salmon.
“It’s extremely difficult to measure mortality rate in wild salmon,” he said. “The idea that we have to demonstrate everything to the last degree in wild salmon is not going to get us to a solution.”
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Photo Courtesy of FIS Member  National Oceanic and Atmospheric Administration NOAA/NMFS
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