When wild salmon go missing it is difficult to pinpoint the cause. Fishing and climate change are the go to culprits.
I believe that when salmon go missing it's a good idea to screen the population for pathogens - easy to do and it narrows the search for the cause. However, salmon disease became a controversial topic when salmon farms were implicated in the spread of disease to wild salmon.
Recently, government is using the decline of Chinook salmon in the Yukon as evidence that salmon farms are not causing wild salmon to vanish. They suggest there is no link between Yukon Chinook salmon and salmon farms, so it can't be salmon farms. This caused me to confirm there is no link between Yukon Chinook and farm salmon.
The answer surprised me.
Yukon Chinook were used to stock salmon farms in southern British Columbia in the early 1990s.
Reproductive material was moved back and forth between the salmon farming company, Creative Salmon, and the Yukon.
Creative Salmon is infected with a virus from Norway called Piscine Orthoreovirus, PRV. It's a controversial virus because some government scientists claim it's local and low risk. Other government scientists report it's from Norway and high risk to Chinook salmon.
Everyone agrees the salmon farming industry is heavily infected with PRV here and in Norway.
PRV enters the red blood cells of Chinook salmon, uses the cells to make copies of itself and fills the cells with virus. Farm salmon infected with it often float motionless at the edge of pens desperate for oxygen. In the wild, infected fish would struggle to migrate up a river.
The migration of the Yukon Chinook is exceptionally long.
Below is a partial record of the relationship between Yukon Chinook and salmon farms.
I suggest Yukon Chinook salmon be tested for PRV just to confirm has not made it into the watershed.
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January 5, 1995 minutes of the DFO Fish Transplant Committee meeting in Vancouver state: “... there was a recent escape of Yukon River Chinook salmon from a salmon farm in the Clayoquot area. These fish are unmarked and thus cannot be recognized as farmed fish.”
In 1995 researchers in the Department of Veterinary Microbiology, Western College of Veterinary Medicine report a newly discovered disease in BC Chinook salmon farms and they note that progeny of Yukon Chinook were “diagnosed with marine anemia.” “Marine anemia, also known as plasmacytoid leukemia, is a recently described disease affecting farmed chinook salmon in British Columbia. The disease has been implicated as the cause of massive mortalities in salmon farms in BC, it has been suggested that, like retroviral leukemias of other animals, marine anemia could spread throughout the population at risk…”
“Progeny” means these were live Chinook originally from the Yukon. This paper only reports on farm salmon hatcheries and sea pens, suggesting these fish were born in a farm hatchery from eggs taken from the Yukon.
March 2005 Creative Salmon makes a case for a continued relationship with Yukon Chinook in a presentation: “Creative Salmon began its relationship with the Yukon in 1990, Yukon River Chinook are well known for their rich color and high fat content… 1990-1996 – Eggs and Milt collected under a commercial fishing licence – Eggs were fertilized at the Whitehorse hatchery.” Creative Salmon was established in 1990, so Yukon Chinook were used from the earliest days of this company.
They report collecting milt at Minto and Whitehorse Hatchery and suggest “Possible joint ventures in the future”. “We ask that Creative Salmon be allowed to continue with the support of the Yukon Salmon Committee and the public it represents.”
The document goes on to say “1996 was the last time eggs were collected” however in 2019 Creative Salmon reports they had Yukon Chinook milt that was frozen in 1999.
Dec 5, 2019 CBC reports Creative salmon in Clayoquot Sound “handed over about 11 years worth of collected milt - salmon sperm - to the Carcross/Tagish Energy Corporation in Yukon… Creative Salmon Company had planned to use the cryopreserved sperm, which had originally been collected from the Yukon River, for salmon farming – but never did.”
The article goes on, “The Yukon company was happy to take the milt. CEO Nelson Lepine describes it as a sort of insurance policy against any sort of devastating collapse of the Yukon River chinook population.
"We're not saying that will happen, but nobody really knows," Lepine said.
"If some worst case scenario occurs, at least this way would we be able to potentially bring back the salmon in a bigger way."
A local radio station reports the Energy Corporation signed an agreement with Creative Salmon and received enough the milt from Creative to fertilize a million eggs. The link is broken, but it still appears in a Google Search:
Summary
- Yukon Chinook salmon are closely linked to a salmon farming company called Creative Salmon with a history of infection with a Norwegian virus - Piscine orthoreovirus (PRV).
- Yukon Chinook that were put in salmon farms in the early 1990s were infected with salmon leukemia.
- Creative Salmon took milt from the Yukon, held it in their facility for 20 years and then returned it to the Yukon.
None of this is proof that farm salmon disease is causing unexplained collapse of specifically the Yukon Chinook, but it does means Yukon Chinook salmon are closely linked to a salmon farming company with a history of infection with a virus known to weaken salmon. I think it only makes sense to test these fish for PRV and sequence the virus if found so it can be traced to source.