A new report provides preliminary information on how last month's Chilcotin River landslide has affected salmon populations that migrate up the Chilcotin and Fraser rivers each year to spawn.
Monitoring shows that the number of salmon moving upstream in August has declined, but the exact extent of the disruption is not yet clear.
“The landslide has certainly played a role in slowing the migration,” said Scott Hinch, a salmon ecologist at the University of British Columbia. “The question is whether it has slowed it down to the point where these fish can’t complete the migration up the Chilcotin.”
According to Update from the Pacific Salmon Commission More than 500 sockeye were spotted upstream of the slide on Friday — less than one-fifth of the approximately 2,664 sockeye researchers expected to arrive under normal migration conditions at this stage of the movement.
In late July, a landslide blocked the Chilcotin River near Farwell Canyon, about 285 kilometers north of Vancouver. The canyon is a landmark for salmon that run to Chilko Lake, where they spawn.
Hinch said the landslide physically blocked some salmon passage. He said debris that subsequently filled the river could alter the salmon's perception of the water and prevent them from finding their way to Chilko Lake.
Hinch noted that because the Chilcotin River banks are still unstable, sockeye salmon could face new obstacles on their way upstream.
There are no sockeye salmon in the Chilcotin River
IN own bulletin fridayThe Tŝilhqot'in National Government said the Chilcotin River's Chinook and Sockeye salmon runs were in danger of disappearing this summer. To help them recover, the countries have declared a year-long pause on fishing in the affected streams.
“We're telling people, stay away, every last salmon counts right now,” Chief Joe Alphonse, chairman of the Tshilhqot'in National Government, told CBC News on Tuesday.
This means that many members of these countries will have to adapt, as sockeye salmon spawning is an important food source for the Chilcot peoples.
“We have made great sacrifices to protect our salmon,” he said. “They are the most important resource we have, other than our people.”
Alphonse said his country is turning to nearby fisheries to provide more food for its members. He added that many members will turn to ice fishing when winter arrives.
Alphonse said that even though the dam has been breached, there are still silt deposits and debris banks blocking the fish. But as water continues to flow through the Chilcotin, it breaks down those barriers.
“Every day, more and more of the natural path that sockeye salmon are used to is being created,” Alphonse said.
Jeff Grout, director of salmon management for the federal Department of Fisheries and Oceans (DFO), said it was too early to tell how much the slide had affected the run. He said DFO had installed new tools to monitor salmon upstream of the slide.
“We're not seeing a lot of salmon migrating through the landslide area at this point, but we also don't expect there to be a lot of salmon there yet,” Grout said Monday.
Grout said that while this summer's cohort was one of the largest in B.C., DFO expected it to be smaller than usual. The company has not issued any active sockeye fishing licenses in the river system this year.
Sockeye salmon move in cycles that repeat roughly every four to five years. Much of this summer run is the offspring of the sockeye that were affected by the Big Bar landslide in 2019.
While this year's race will be challenging, Hinch said their parents overcame similar challenges.
“They're actually quite adept at getting through difficult terrain and obstacles,” he said. “Let's hope they can get through this one as well.”
Researchers expect about 117,000 sockeye salmon to attempt to reach Chilko Lake this summer.
Grout says the extent of the landslide's impact on salmon will become clearer next week, when most of the sockeye are expected to move upstream.