While fish-farm companies operating in the Discovery Islands are turning to the courts to challenge the federal Fisheries minister鈥檚 recent decision to end aquaculture in that region, new research provides evidence the salmon farming industry may be responsible for the introduction and spread of a highly infectious virus to B.C.鈥檚 endangered wild salmon stocks.
Researchers at the University of British Columbia, Fisheries and Oceans Canada, the University of Toronto and elsewhere analyzed the genomes of all publicly available Piscine orthoreovirus-1 (PRV-1) samples, dating back to 1988, as well as newly sequenced PRV-1 genomes from the northeast 91原创. The results suggest the industry may have introduced the virus strain from Atlantic salmon farms to those in the 91原创, which in turn spread it to our wild fish populations.
Despite Atlantic salmon being introduced to the region in the early 1900s, the study鈥檚 results indicate the virus arrived here only recently. The researchers revealed that a lineage of the virus now found in the 91原创 diverged from that in the Atlantic Ocean in 1989, predating the first report of disease from the virus in 2002. This suggests that PRV-1 was introduced to the northeast 91原创 at about the same time as salmon farms in the region imported Atlantic salmon eggs from Europe.
The data also indicate that 97 per cent of fish in all Atlantic salmon farms were infected 18 months into their production cycle, suggesting the farms were the source of the virus in the local environment.
The study, published last week in the journal Science Advances, helps to clarify the industry鈥檚 role in the virus鈥檚 spread.
Piscine orthoreovirus-1 causes heart and skeletal muscle inflammation in Atlantic salmon. A 2018 study indicated PRV-1 shows up differently in Chinook salmon, affecting the fishes鈥� kidneys and livers instead. The 2018 researchers also found no consistent genetic differences in the variants causing either disease, which suggests that migratory Chinook salmon may be at more than a minimal risk of disease from exposure to the high levels of virus occurring in B.C. salmon farms.
The PRV-1 virus is a strain of the PRV virus. Other PRV strains have been shown to cause diseases in Chinook and Coho salmon and trout that lead to heart and skeletal muscle inflammation, jaundice, anemia and other symptoms. In some cases, the diseases can kill up to 20 per cent of infected wild 91原创 salmon.
The province鈥檚 wild salmon stocks face other challenges, as well. From sea lice to sea lions and seals, from warming ocean and river temperatures to low river levels, from river and estuary pollution to habitat loss and river obstructions such as the Big Bar landslide that has blocked passage up the Fraser River since 2018, wild salmon have much to dodge and overcome during their short lifetime.
In December, federal Fisheries Minister Bernadette Jordan announced that salmon farm licences for the Discovery Islands areas would be renewed for 18 months only, with no licences issued or renewed thereafter. By June 30, 2022, open-net salmon farms in the region are to be shut down.
Nineteen fish farms operate in the region, employing or indirectly providing jobs to more than 1,500 people.
Earlier this year, the minister also banned the transfer of smoults from hatcheries to the farms鈥� ocean pens.
The Cohen Commission鈥檚 2012 report identified the Discovery Islands as a bottleneck along wild salmon migration routes and recommended eliminating fish farming in the region. The recommendation was conditional on Fisheries and Oceans finding more than a minimal risk to migrating sockeye by September 2020.
Nine peer-reviewed risk assessments to determine the farms鈥� impact on wild salmon have been completed. They concluded that the risk of the transfer of pathogens to wild stocks is minimal.
Several aquaculture companies operating in the region are challenging the minister鈥檚 decisions in court.
In April, a federal court judge granted the companies an injunction suspending the ban on restocking their farms. The injunction doesn鈥檛 force the minister to grant the transfer licences, but it does require the minister to consider whether to grant the licences without regard to next year鈥檚 closing of the farms.
The broader challenge to the decision to close the farms is still in process.
