A new report sheds light on how last month’s landslide has affected salmon populations that enter the Chilcotin and Fraser rivers each year to spawn.
Monitoring activities reveal that the number of salmon migrating upstream in August has declined – but the exact scale of the disruption is not yet known.
“The landslide has certainly played a role in slowing migration,” said Scott Hinch, a salmon ecologist at the University of British Columbia. “The question is whether it has slowed migration to the point where these fish can’t complete their migration up the Chilcotin.”
According to update from the Pacific Salmon Commission On Friday, more than 500 kidneys were spotted above the landslide — less than a fifth of the approximately 2,664 kidneys researchers expect to arrive under normal migration conditions at this stage of the expedition.
In late July, a landslide blocked the Chilcotin River near Farwell Canyon, about 176 miles (285 kilometers) north of Vancouver. The canyon is a landmark on the way for salmon to spawn at Chilko Lake.
Hinch said the landslide physically blocked some salmon from crossing. He said the contaminants that later saturated the river could change the way salmon perceive the water and could make it harder for them to find their way to Chilko Lake.
Hinch said that because the banks of the Chilcotin River are still unstable, the kidney could encounter more obstacles on its way upstream.
No sockeye salmon catch in Chilcotin River
In its bulletin Friday, the Tŝilhqot’in Nation government said this year’s summer populations of Chinook and Sockeye salmon in the Chilcotin River are at risk of extinction. To help them recover, the nations have announced a one-year halt in fishing the affected populations.
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 landslide had affected runoff. He said DFO had installed new tools to monitor salmon upstream from the landslide.
“We are not seeing any active salmon migration through the landslide area at this point, but we do not expect large numbers of salmon to be there right now,” Grout said Monday.
Grout said that while this year’s cohort was one of the largest batches of sockeye salmon in British Columbia, DFO expects the batch to be smaller than usual. No licenses have been issued for sockeye salmon fishing in the river system this year.
Sockeye salmon migrate in cycles that repeat themselves about every four to five years. Most of this summer are offspring of sockeye salmon that were challenged by the 2019 Big Bar landslide.
“We had historically low returns back then, and as a result, that will lead to low numbers of offspring,” Grout said.
Hinch said this year’s race will present challenges, but their parents have overcome similar difficulties.
“They’re actually quite adept at getting through difficult areas and obstacles,” he said. “Let’s hope they can get through this.”
Scientists estimate that about 117,000 sockeye salmon will attempt to reach Chilko Lake this summer.
Grout says the scale of the landslide’s impact on salmon will become more apparent next week, when most sockeye salmon are expected to head upriver.
