Alaska Chinook salmon study requiring lethal sampling during worst-ever run draws Yukon criticism

Researchers with the Alaska Department of Fish and Game have killed 452 Yukon River Chinook to examine them for ichthyophonus, a disease-causing pathogen that may be causing salmon to die mid-migration. The study comes during the smallest run ever recorded.

Researchers studying ichthyophonus, parasite that might cause Yukon River Chinook to die during migration

Chinook salmon swim by the Whitehorse fish ladder in this stock photo. An Alaska study on a parasite inflicting Yukon River Chinook is drawing criticism because it requires lethal sampling of fish. (Claudiane Samson/Radio-Canada)

An Alaska study of a parasite in Yukon River Chinook salmon is facing criticism in the Yukon due to researchers lethally sampling fish during the worst season on record.

Researchers with the Alaska Department of Fish and Game (ADF&G) have killed 452 fish to examine them for ichthyophonus, a disease-causing pathogen that may be causing Chinook to die mid-migration.

However, fewer than 45,000 Chinook entered the river this season and just more than 11,000 have entered Canada. A minimum of 42,500 fish, under an international agreement, are supposed to make it to their Yukon spawning grounds. 

The run is the smallest recorded and marks the fourth season in a row where minimum spawning escapement goals have not been met. 

"At this point, people think that we're at a biological tipping point which means we need to ensure that every salmon reaches their spawning ground, if possible," said James MacDonald, chair of the Yukon Salmon Sub-Committee. 

"To consciously take out salmon for biological sampling doesn't make sense for folks given that we're at some kind of turning point or precipice for the survival of these salmon stocks."

The first Chinook salmon of the season reached the Whitehorse dam this weekend, but the numbers of Chinook on the Yukon River remain disastrously low for yet another year. Elyn Jones spoke with Cheyenne Bradley, the Kwanlin Dün First Nation's land steward officer about the salmon situation.

Compounding frustrations is the fact many Yukon First Nations have voluntarily abstained from harvesting Chinook.

"It is really concerning because on this side of the border, we're really being deprived of our traditional foods," said Tr'ondëk Hwëchin Hähké (Chief) Roberta Joseph, whose First Nation is in its ninth year of not fishing.

"Although scientific information is important… those salmon that are being used [for the study] are not going to make it to spawning grounds, so that will be that much less salmon on the return of this run in the future." 

Chinook killed for the study will be shared with local communities. Fifty fish were taken at Eagle, Alaska, near the Yukon border, and half were set aside for Fisheries and Oceans Canada (DFO) to distribute to Yukon First Nations.

'This is not just a study for study's sake'

While the presence of ichthyophonus isn't new, the urgency to understand its impact on migrating Chinook has increased in recent years. 

In particular, scientists on both sides of the border have been stumped by the major discrepancy between the number of Canadian-origin fish counted near the mouth of the river at Pilot Station and the number that show up at Eagle.

Up to 30,000 Chinook have "disappeared" in-river.

"It's incumbent on us to try and figure out where those fish are going," Zach Liller, the research coordinator for ADF&G's Arctic-Yukon-Kuskokwim region, said in an interview. 

ADF&G, the U.S. Fish and Wildlife Service and DFO identified ichthyophonus's role, if any, in the disappearance of Chinook as a "very high-priority investigation" in the preseason, Liller said. That was when the outlook for the 2022 run wasn't as dire. 

Ichthyophonus infections, which Chinook pick up in the ocean, can only be confirmed by looking at a fish's flesh and organs and seem to ebb and flow in several-year-long cycles, with Chinook appearing to be in a peak period now. Liller said it was "incredibly unfortunate" that the peak aligned with the "very low abundance" of the 2022 run, but explainedthe study needed to take place while infections are high in order to get meaningful data. 

"If, in fact, ichthyophonus is linked to mortality at the magnitude we hypothesize it might be, it really is incumbent on us to document that, get a handle on it… and [turn] the results of a study like this into advice for fisheries managers so they can deal with it when it does occur," Liller said.

"This is not just a study for study's sake." 

2022 is shaping up to be the worst-ever Chinook salmon run on the Yukon River. But it's more than just the number of fish at risk, it's culture and a way of life. CBC's Jackie Hong spoke with people about Chinook and shared their stories.

The study was modified in late July after DFO's Yukon office sent a letter to ADF&G urging it to not kill any fish at Eagle. 

Marc Ross, a fisheries manager with DFO in Whitehorse, said the letter came after the department received "a lot of feedback from concerned stakeholders" about the impact of lethal sampling on the low run, on top of DFO's "own internal concerns." 

ADF&G didn't comply but instead reduced the number of Chinook collected at Eagle. Liller said at that point, the majority of sampling had been completed at Pilot Station and mid-river and "there were strong concerns those sacrifices would have been made in vain" had the study been stopped.

Researchers ultimately took 202 Chinook at Pilot Station, 200 mid-river and 50 at Eagle. 

ADF&G is sharing the study's findings with DFO. According to Ross, the preliminary results suggest ichthyophonus is infecting 40 to 50 per cent of fish.

'It's just outrageous'

The Yukon Conservation Society's fish and wildlife analyst is still not convinced the study is worth the cost. 

In an interview, Sebastian Jones said he first heard about the study last year from Alaska scientists who were already concerned about the impact it might have on spawning escapement. 

"As the total population of salmon goes down, the impact of killing these fish goes up," Jones said, adding that, with the number of Canadian-origin Chinook only in the thousands, the loss of even a few hundred fish was "huge."

"In my opinion, [the study] wasn't justifiable to begin with and it's actively harmful now —  it's just outrageous." 

While Jones said some people think ichthyophonus might be the "smoking gun" behind plummeting Chinook numbers, he thinks it's "almost certainly not" the reason and other factors are at play.

"It's because we have messed with the ecosystem, primarily out in the ocean, combined with overfishing on the Yukon River that has genetically altered our salmon so that they're no longer able to thrive," he said. 

"And killing more fish, chasing after another excuse for poor management, is not going to fix the problem." 


Jackie Hong


Jackie Hong is a reporter for CBC North in Whitehorse. She was previously the courts and crime reporter at the Yukon News and, before moving North in 2017, was a reporter at the Toronto Star where she covered everything from murder trials to escaped capybaras. You can reach her at