B.C. landslide blocks Chilco sockeye access to spawning ground, threatening the hearty ‘superfish’

In Tŝilhqot’in country, the summer calendar is set by the salmon.
Every year, as the famed Chilko Lake sockeye return to spawn and die, hundreds of Tŝilhqot’in celebrate with their annual Nation Gathering on the banks of the Chilcotin River in British Columbia. The main events include fish cutting, fish eating and a hotly-contested fishing derby.
This year, owing to a landslide that’s blocked their way, it may feel more like a wake than a celebration.
“No fishing derby this year,” laments Joe Alphonse, tribal chair of the Tŝilhqot’in National Government, which represents roughly 4,000 people in six communities located between the Fraser River and the lee side of the Coast Mountains in west-central B.C. “The Nation Gathering is usually a celebration of sockeye, but there won’t be any this year.”
The Chilcotin is a tributary of the Fraser River, once the world’s foremost sockeye factory with annual returns of 100 million fish, which comprised up to 80 per cent of the regional diet in times before European contact. Today, stocks throughout the Fraser basin, an expanse of land nearly the size of the United Kingdom, are a fraction of what they once were, but First Nations and scientists often point to the hardy Chilko sockeye as a source of hope. Dubbed a “superfish” by one researcher, its heart, aerobic capacity and shape have all evolved to tolerate arduous swims in hot conditions – a fish for a warming world.
All that optimism changed in a matter of minutes late last month when a kilometre-long stretch of mountainside slumped into the Chilcotin, blocking the river for days and imperiling the Chilko sockeye’s passage to spawning grounds. Only a handful of fish have been able to pass through the slide zone to date, casting doubt over the future of the superfish – and perhaps the future of Fraser salmon.
“It’s looking pretty bleak, isn’t it,” Mr. Alphonse says.
Hand-wringing about salmon declines on the Fraser are woven into the provincial fabric. Countless inquiries have examined the matter over the last century and a long list of culprits have been identified: pulp-mills, farmers, dam operators, fish-farmers, fishers, loggers and climate change.
Then-prime minister Stephen Harper launched the most recent investigation in 2009 when only 1.36 million sockeye returned to the river. The $30-million Cohen Commission blamed a complex interplay of factors and urged government to boost research, limit open-pen salmon farming and protect habitat.
Fifteen years later, the sockeye runs have dwindled to a fraction of that panic point. Just 288,000 sockeye returned to the Fraser in 2020, a record low owing partly to the 2019 Big Bar rock slide that trapped migrating salmon. This year, forecasted sockeye returns are scarcely higher; the Pacific Salmon Commission’s most recent guess is 460,000 based on counts using hydrostatic sensors.
The numbers are bleaker on the Chilcotin. Since July 30, sonar has detected 31 chinook and 16 sockeye passing through the slide area, according a report from the Tŝilhqot’in National Government’s Salmon Emergency Task Force. They were hoping for 150,000, already down significantly from the 500,000 or more that used to crowd Chilko Lake before the Big Bar slide.
Those counts represent the collapse of a fish that once sustained much of what is now B.C., yet the outcry that marked 2009 has been replaced with a sense of resignation.
“I’m not optimistic about the future of salmon here frankly,” said David Levy, a fisheries scientist who served as science director for the Cohen Commission. “I don’t really see the value in more inquiries.”
That’s partly because there’s a rare scientific consensus on the biggest threats now facing Fraser salmon, and no single company or government can be blamed for them: heat and drought.
Professor Scott Hinch, who has authored or co-authored some 300 papers on Pacific salmon, recalls a sweltering summer day in 1994, when the paramount importance of temperature to salmon survival became apparent to him. He was monitoring salmon runs around Hell’s Gate, the violently rapid stretch of the Fraser about 200 kilometres upstream from Vancouver, when he noticed the tagged fish he was tracking turning around and going downstream.
“It was one of those watershed moments,” said Dr. Hinch, who runs the Pacific Salmon Ecology and Conservation Laboratory at the University of British Columbia. “The temperature went up a couple of degrees and they all went downstream, many never to be seen again.”
Today, the Fraser routinely runs about two degrees warmer than its historic mean. At 18 degrees, salmon swimming performance becomes sluggish. Twenty degrees is associated with high prespawn mortality and disease. This summer, the Fraser water temperatures have topped 21 degrees, killer heat for most salmon.
But not all salmon.
For years, Erika Eliason has been testing the physical limitations of salmon with a device best described as a fish treadmill, a water-filled tunnel capable of creating variable speeds and temperatures. Like a cardiologist conducting a stress test, she measures heart rate, oxygen levels and metabolic rates as the fish face changing currents. She’s found that the Chilko sockeye have the highest temperature tolerance of all the populations she’s measured, capable of coping with temperatures as high as 26 degrees. She’s called them “superfish.”
“Even so,” said Dr. Eliason, an ecophysiologist and associate dean at Kwantlen Polytechnic University, “it’s really getting warm for those fish. On the flip side, they are resilient. And it’s been shown they can adapt pretty quickly. I’m an optimist, but I do think that we need to sound the alarm so that people pay attention and do what’s necessary to protect spawning grounds, protect migration corridors.”
Salmon have an “unstoppable ability to adapt,” writes Mark Kurlansky in his 2020 book on the fish. “When confronted with environmental changes, they make genetic adjustments.” How fast they can adapt is a subject of continuing study. Some West Coast species may already be moving north, and have shown up in Arctic spawning beds.
Still, Dr. Hinch doesn’t expect a complete extinction of Fraser salmon any time soon. “It’s just that the levels may be so low that fisheries may not be viable anymore,” he said. “We haven’t seen any extirpations, any stocks disappearing entirely.”
Mr. Alphonse wants to keep it that way. “It’s time to work together,” he said, “or we won’t have any wild sockeye left.”