Scientists are warning some salmon runs in B.C.’s Fraser River could disappear completely, as a landslide that came down a year ago continues to block a critical fish migration route.
In a presentation to the Pacific Salmon Commission last month, Fisheries and Oceans Canada scientists said there is a “meaningful chance of extinction” for three salmon runs due to the Big bar landslide: the early Stuart sockeye and the Mid-Fraser and Upper Fraser spring 1.3 chinook populations.
In addition, three more runs are at “considerable risk” depending on how operations to clear the slide play out in 2020, including the early summer sockeye, summer sockeye and Mid-Fraser summer 1.3 chinook.
The discovery of the slide in a remote area northwest of Kamloops this past June sparked a massive response from federal, provincial and First Nations officials, who transported more than 60,000 fish up the river with helicopters and trucks.
The slide, which is believed to have come down between October and November last year, created a five-metre waterfall that made it nearly impossible for millions of salmon to make it to their natural spawning grounds upstream.
The federal scientists said many of the transported salmon were “likely very stressed,” with many of the chinook and sockeye found in poor health — most likely due to exhaustion from their efforts to make it past the slide themselves.
While roughly 275,000 salmon were able to make it through the waterfall as of mid-October, few of them have been able to spawn, the scientists said.
For example, out of approximately 21,000 early Stuart sockeye that entered the Fraser River past Mission, less than 100 ended up spawning.
Crews have also spent months attempting to clear the slide, scaling and blasting the rockface to recreate the passageway.
Despite that work, however, the scientists said no rock has been removed from the slide area, and the “rock manipulations have been inconsequential to establish passage for salmon around the slide.”
A progress report posted by the provincial and federal response team earlier in November said it is planning for future winter construction to remove rock from the area and further scale the rocks.
Road construction for crews is set to happen at the beginning of the year ahead of the spring freshet in March, when water levels are set to rise from winter lows.
The team is also awaiting final results from its radio tagging and monitoring program to further determine the effectiveness of the fish transport program.