Scientists find deadly bacterial disease in wild B.C. salmon for first time
UBC and Pacific Salmon Foundation researchers discovered tenacibaculosis — a disease that causes skin ulcers and death — in wild Chinook salmon off Vancouver Island.
The day's top stories, food & events — every morning at 7. Unsubscribe anytime.
Scientists have discovered a deadly bacterial disease in wild B.C. salmon for the first time, raising new questions about what's harming the Pacific populations that southern resident orcas depend on.
Researchers from the University of British Columbia and the Pacific Salmon Foundation found tenacibaculosis — a disease causing skin and fin ulcers and fish mortality — in wild Chinook salmon sampled off the west coast of Vancouver Island. The bacteria, Tenacibaculum dicentrarchi, was found in 16 per cent of the 99 Chinook sampled.
The discovery was accidental. In 2022, UBC scientists studying catch-and-release impacts in Barley Sound noticed unusual bacterial lesions developing on some fish just in front of the tail. "We spend enormous effort trying to understand why wild salmon die in the ocean. This study gives us one of the clearest pieces of evidence that links bacterial disease to mortality in wild Pacific salmon," said Katie Zinn, co-author and researcher with UBC's Pacific Salmon Ecology and Conservation Lab.
The team collaborated with the Pacific Biological Station, the University of Toronto, and the University of California, Davis. "This is the first time tenacibaculosis has been diagnosed in wild-caught fish, providing empirical evidence that Tenacibaculum bacteria can negatively affect wild fish health and contribute to disease burden in B.C. wild salmon," said Emiliano Di Cicco, lead author and fish health researcher with the Pacific Salmon Foundation.
Tenacibaculosis is one of the most common diseases in farmed Atlantic salmon in open-net pens in B.C. and the leading cause of farm mortality. Common symptoms include lethargy, loss of balance, abnormal swimming behaviour, and oral ulcers.
Finding sick wild fish is extremely challenging. Once infected, wild salmon are quickly caught by predators or become too weak to feed and starve. Researchers noted that handling fish during capture and holding may have increased vulnerability to infection by damaging their protective mucus layer.
The Pacific Salmon Foundation noted that the DFO doesn't account for Tenacibaculum dicentrarchi in its existing disease assessment for the closely related Tenacibaculum maritimum. These bacteria are currently not regulated in B.C. as a risk to wild Pacific salmon.
How do wild salmon become infected with this bacteria in the ocean?
Will the DFO update its disease assessment to include this bacterial threat?
We'll update this story as answers emerge.
The facts
What bacterial disease was found in wild B.C. salmon for the first time?
Tenacibaculosis, caused by the bacteria Tenacibaculum dicentrarchi, was discovered in wild Chinook salmon off the west coast of Vancouver Island. The disease causes skin and fin ulcers and fish mortality.
How many wild Chinook salmon tested positive for tenacibaculosis?
The bacteria was found in 16 per cent of the 99 Chinook salmon sampled off Vancouver Island.
When did researchers first notice this disease in wild salmon?
UBC scientists discovered the disease in 2022 while studying catch-and-release impacts in Barley Sound, when they noticed unusual bacterial lesions developing on some fish.
Why is tenacibaculosis a concern for wild salmon populations?
Tenacibaculosis is one of the most common diseases in farmed Atlantic salmon in B.C. and the leading cause of farm mortality. Once infected, wild salmon become vulnerable to predators or too weak to feed and starve, making the disease a potential threat to wild Pacific salmon health.
