According to a report published by researchers at the University of British Columbia, three new viruses have been discovered in endangered Chinook and sockeye salmon populations. One of those viruses is from a group never before shown to infect fish.
It’s not entirely clear yet what the impact of the viruses is on the species’ health, but it is clear that all three viruses are related to ones that cause serious diseases in other species, including mammals such as humans.
“We were surprised to find viruses which had never before been shown to infect fish,” said UBC researcher Gideon Mordecai. “Although there’s no risk to humans, one of the viruses is evolutionarily related to respiratory coronaviruses, and is localized to the gills. That suggests it has a similar infection strategy to its distant relatives that infect mammals.”
Researchers from UBC and Fisheries and Oceans Canada used DNA sequencing followed by tests specific to each virus to screen more than 6,000 salmon from along the British Columbia coast. These test fish included wild, hatchery, and aquaculture fish.
“We found the new viruses were widely distributed in dead and dying farmed salmon and in wild salmon,” said UBC virologist Curtis Suttle. “It emphasizes the potential role that viral disease may play in the population dynamics of wild fish stocks, and the threat that these viruses may pose to aquaculture.”
One new virus infected more than 15 percent of hatchery Chinook salmon tested. Another was detected in 20 percent of Chinook from fish farms but was only found in adult or sub-adult salmon. Generally speaking, the new viruses were more commonly found in farmed fish than in wild fish.
Over the past 30 years, stocks of Chinook and sockeye salmon have declined steadily, much to the great concern of Indigenous peoples who rely on the fish for subsistence, and to commercial and recreational fishers and the general public.
“It’s essential that we determine whether these viruses are important factors in the decline of Chinook and sockeye salmon stocks,” Suttle said. “The research highlights the need for robust surveillance to improve our understanding of how viruses might impact the health of wild Pacific salmon populations.”
The findings of the team’s research will aid conservation efforts by helping scientists figure out how widespread the viruses are in these fish. The team’s future work will focus on determining the risks these viruses pose to salmon health and investigating the ease with which viruses can be exchanged between hatchery farmed, and wild salmon populations.
Photo: Sockeye salmon spawning. Credit: Shutterstock