A University of Toronto study has found the environmental DNA of pathogens harmful to fish are 2.7 times more likely to be detected near active salmon farms versus inactive sites. (Kenny Regan photo)

A University of Toronto study has found the environmental DNA of pathogens harmful to fish are 2.7 times more likely to be detected near active salmon farms versus inactive sites. (Kenny Regan photo)

DNA presence of pathogens harmful to fish almost triples near B.C. salmon farms: study

Industry, DFO caution the research does not correlate to disease transmission

Wild salmon may be almost three times more likely to encounter harmful pathogens near salmon farms, a new study has found.

Scientists from the University of Toronto spent three years testing at 58 sites along the B.C. coastline, finding the environmental DNA (eDNA) of 22 viruses, bacteria and other microscopic organisms had a 2.72 times higher probability of being detected near active salmon farms, versus inactive sites.

The pathogens are naturally occurring in B.C. waters but stocked farms have the potential to act like reservoirs of hosts for pathogens.

Lead researcher, Dylan Shea, a PhD candidate at the university’s ecology and evolutionary-biology department, said the occurrence of DNA varied by times and location, adding the study relates only to the presence of DNA, not the risk of infection to fish.

“There are many unknowns between what we observed and the disease implications for any given fish species … but the findings themselves convey a pretty important message. I can say with confidence that salmon farms do increase the risk of exposure to the suite of microparasites we studied.”

Two of the most commonly detected agents include the Erythrocytic necrosis virus, which attacks red blood cells, affecting a fish’s metabolism, and Candidatus Syngamydia salmonis, causing swelling of the internal organs and skin lesions, which can potentially lead to secondary infections.

The study was published in the scientific journal Proceedings of the Royal Society Oct. 21.

READ MORE: Minimal risk to wild salmon from viruses on farmed B.C. salmon: Fisheries Department

Veterinarians on salmon farms verify young salmon are free from a variety of pathogens, including some identified in the recent study, before they’re transferred to open-net pens. The fish undergo regular screenings thereafter.

Shawn Hall, a spokesperson for the B.C. Salmon Farmers Association, said there are other cautions to note in the latest research.

“The study did not look at viable pathogens, but rather fragments that don’t necessarily cause any concerns related to disease,” Hall said. “Also, the study did not test any control sites – different areas of the ocean. Samples were only taken near operating or fallowed salmon farms. Based on this major exclusion of other test sites, it is clear that study results lacks the comprehensive research support.

“Good science and protecting wild salmon will always be the foundation of responsible ocean-based salmon farming in BC. New studies always needs to be looked at with a critical eye focused on how the research was conducted.”

The David Suzuki Foundation, which supported the study, said in a statement the findings call into question recent DFO risk assessments that found the transfer of nine pathogens from farms to wild fish did not pose a significant threat to wild populations, some of which are at their lowest numbers on record. The assessments were spurred by the 2012 Cohen Commission inquiry that recommended a prohibition on salmon farms in the Discovery Islands by September, 2020, if the threshold for disease transmission exceeded “minimal risk”.

“Uncertainty should inspire precaution,” David Suzuki Foundation marine conservation specialist Kilian Stehfest said. “The study’s findings further highlight the importance of applying a precautionary approach when making management decisions based on incomplete evidence with high levels of uncertainty.”

DFO is currently consulting with area First Nations before deciding later this year on whether to renew aquaculture licences in the Discovery Islands. A DFO spokesperson said the University of Toronto study is among many that will be reviewed and incorporated into the fisheries minister’s decision, but stressed the implications of the latest research are still unclear.

“Exposure to pathogen(s) alone is not sufficient to cause disease — the nature of the host, environmental conditions, and exposure dose and duration are all factors that play a role, and are analyzed when assessing risk.”

READ MORE: B.C. salmon farm opponents demand answers from DFO



quinn.bender@blackpress.ca

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Penny Hart is calling on the community to help find her son Sean Hart who was last seen on Nov. 6 at a health institution in Saanich. (Devon Bidal/News Staff)
Search spreads for Saanich man missing from mental health facility for nearly a month

Family hopeful as possible sightings reported across Island and in Vancouver

The Sooke School District is actively looking for more bus drivers after they had to cancel a handful of bus routes in late November. (Black Press Media file photo)
Bus driver shortage cancels routes in Sooke School District

More drivers needed to accomodate expanding bus routes amid pandemic

Victoria’s Royal Jubilee Hospital took in two COVID-19 patients from Northern Health as part of a provincial agreement. (Black Press Media file photo)
Victoria hospital takes in two COVID-19 patients from Northern Health

Royal Jubilee Hospital takes patients as part of provincial transport network

Joe Robertson and Jack Amos ran the length of Vancouver Island, with the help of their van Pippi, raising more than $12,000 for 1Up Victoria Single Parent Resource Centre. (Photo submitted)
Greater Victoria pair finishes running length of Vancouver Island a day early

Joe Robertson and Jack Amos raised more than $12,000 for single parents

Island Health is expanding COVID-19 testing in Nanaimo with a new testing location at Vancouver Island University. (News Bulletin file photo)
Island Health issues apology over racist practices in health care system

Report by Mary Ellen Turpel-Lafond finds ‘widespread systemic racism against Indigenous people’

(AP Photo/Paula Bronstein)
POLL: Has COVID-19 changed your plans for the holidays?

The lights are going up, the stacks of presents under the tree… Continue reading

Anyone with information on any of these individuals is asked to call 1-800-222-TIPS (8477) or visit the website victoriacrimestoppers.ca for more information.
Greater Victoria Crime Stoppers wanted list for the week of Dec. 1

Greater Victoria Crime Stoppers is seeking the public’s help in locating the… Continue reading

Provincial health officer Dr. Bonnie Henry updates B.C.’s coronavirus situation at the legislature, Nov. 30, 2020. (B.C. government)
Hockey team brought COVID-19 back from Alberta, B.C. doctor says

Dr. Bonnie Henry pleads for out-of-province travel to stop

B.C. Premier John Horgan on a conference call with religious leaders from his B.C. legislature office, Nov. 18, 2020, informing them in-person church services are off until further notice. (B.C. government)
B.C. tourism relief coming soon, Premier John Horgan says

Industry leaders to report on their urgent needs next week

BIG SALMON ranch in Washington State. (Center for Whale Research handout)
Non-profit buys Chinook ranch in hopes of increasing feed for southern resident killer whales

The ranch, which borders both sides of Washington State’s Elwha River, is a hotspot for chinook salmon

Natalie MacMaster and Donnell Leahy are inviting audiences into their home for ‘A Celtic Family Christmas’. (Submitted)
Natalie MacMaster coming to you through Cowichan Performing Arts Centre

Here’s your chance to enjoy the famed fiddler in an online show with her husband Donnell Leahy.

An 18-year old male southern resident killer whale, J34, is stranded near Sechelt in 2016. A postmortem examination suggests he died from trauma consistent with a vessel strike. (Photo supplied by Paul Cottrell, Fisheries and Oceans Canada)
“We can do better” — humans the leading cause of orca deaths: study

B.C. research reveals multitude of human and environmental threats affecting killer whales

An RCMP cruiser looks on as a military search and rescue helicopter winds down near Bridesville, B.C. Tuesday, Dec. 1. Photo courtesy of RCMP Cpl. Jesse O’Donaghey
B.C. Mountie, suspect airlifted by Canadian Armed Forces from ravine after foot chase

Military aircraft were dispatched from Comox, B.C., say RCMP

Most Read