When young Fraser River sockeye salmon swim past fish farms in the Discovery Islands, B.C., the exposure rate to the harmful pathogen Tenacibaculum maritimum is 12 times higher than elsewhere, according to a new study based on a decade of research by the Pacific Salmon Foundation.
Over 10 years, researchers collected about 2,200 samples from juvenile salmon as they left the Fraser River and migrated to the ocean, travelling between Vancouver Island and the coast of the mainland.
As they swam through the Discovery Islands near Campbell River, which are home to 19 fish farms, the salmon were more likely to pick up the bacterium than in any other location along their route, the study suggests.
Scientist Andrew Bateman, lead author of the publication, argued that the results mean fish farms should be kept from operating along the salmon's migratory route.
"If we are wanting to protect these Fraser River sockeyes, we need to give them the best shot that we can," said Bateman.
"Having salmon farms in the Discovery Islands in the way of their seaward migration is an added risk that we can control."
Fish farms in B.C. waters have long been linked to the spread of pathogens among wild fish, including salmon.
In fish, T. maritimum is an ulcerative disease that can cause illness and sometimes death.
Fish farms off B.C.'s coast
Back in 2020, Fisheries and Oceans Canada (DFO) and then-fisheries minister Bernadette Jordan ordered the closure of 19 fish farms in the Discovery Islands by June 2022.
Part of the mandate letter for the current minister, Joyce Murray, includes the development of a transition plan from open-net pen salmon farming by 2025.
But at the end of April, a federal court judge set aside the DFO's original order, finding that it breached the right to procedural fairness owed to the 19 fish farms that were expected to close.
In response to the latest court ruling and the findings of the new study, Michael Meneer, CEO and president of the Pacific Salmon Foundation, said in a statement that the foundation "strongly encourages" Murray to hold firm to the federal government's commitment to transition away from open-net salmon farming by 2025.
"Salmon face many challenges, and open-net salmon farms pose a serious risk to wild salmon," he said.
"Any renewal of licences that prolong this risk to wild salmon would be deeply concerning."
Pathogens and salmon survival
A second study, released last week by UBC, found that two specific pathogens, T. maritimum and piscine orthoreovirus, most negatively impacted the survival of wild salmon.
For this study, researchers assessed dozens of pathogens among thousands that infect wild salmon along B.C.'s coast.
"Our analyses, which offer the most comprehensive examination of associations between pathogen prevalence and Pacific salmon survival to date, suggest that pathogens in Pacific salmon warrant further attention," the study's authors wrote in their abstract.
CBC News has reached out to the B.C. Salmon Farmers Association for comment. The association has previously stated that the province could lose more than 4,700 jobs and up to $1.2 billion in economic activity annually if salmon farm licences are not renewed.