A salmon expert in British Columbia says a massive landslide that blocked part of Canada’s largest sockeye salmon run has created an unprecedented situation, potentially putting already endangered fish at even greater risk.
Scott Hinch, associate dean of the Pacific Salmon Ecology and Conservation Laboratory at the University of British Columbia, said a 30-metre-high, 600-metre-long pile of trash blocking the Chilcotin River in British Columbia’s Cariboo region could pose a threat to populations of black and sockeye salmon — both while the water is being dammed and when it eventually spills out.
“These are natural phenomena, but what is unusual is that they are occurring at a time when rivers are much warmer than they used to be,” he said in an interview on Thursday.
“And that causes this unprecedented lack of understanding of what will happen to these fish.”
The sockeye salmon are headed to Chilko Lake to spawn. But to get there, they have to swim through Farwell Canyon, about 176 miles north of Vancouver, where a dam of rocks and mud blocks the way.
Dangerously warm water
Provincial and Cariboo Regional District officials say it is unclear whether the reservoir structure behind the dam on the Chilcotin, a tributary of the Fraser River, will crack or be submerged by debris.
British Columbia authorities said the Fraser River could rise hundreds of kilometres as a result of the release, prompting dozens of alerts and evacuations.
Hinch said the warmer Fraser River is already nearly lethal to salmon, and if they are not allowed to move to cooler, glacier-fed waters, it could be dangerous for the fish.
“So what’s happening now is that the reduced flow of water downstream will make that water warmer to begin with. It will probably be less accessible,” he said.
“So these fish will be in warmer water and low flows, either in the Chilcotin system or the Fraser system.”
The Tŝilhqot’in government has declared a local state of emergency after a landslide blocked the Chilcotin River in British Columbia’s Cariboo region.
Williams Lake First Nation Chief Willie Sellars said the salmon situation is “extremely concerning.”
He added that the First Nation is concerned about what will happen to fish if the large lake that collects behind the landslide bursts.
“What’s that going to do to all those sockeye and chinook that are coming up the Fraser River to spawn in other tributaries?” he said.
Pollution can create new barriers
Hinch said one problem is there is no way to predict how debris flowing down rivers will ultimately settle.
“If it’s not full barriers, then there could be partial barriers, there could be areas where it’s harder for fish to move through,” Hinch said.
“Remember, these fish stopped feeding about a month ago. They’re migrating to the reserves anyway.”
There is also a risk that new rocks and debris in the water could affect the salmon’s ability to navigate by smell, a skill they already have as fry.
“They are imprinted on the unique chemicals that are in their parent river basin. That chemistry is disrupted by the landslides because now other organic chemicals are coming into the river in high concentrations that are not part of the scent of their parent stream,” he said.
Sellars said the year was already expected to be weak.
“Maybe it’s better that it happened in a low-level year, but it’s also very devastating to the current that’s going to be flowing up the Chilcotin, and in four years there won’t be any fish left,” he said.
At a news conference on Thursday, Minister for Water, Land and Resource Management Nathan Cullen said the government knows water is critical spawning habitat for salmon and other fish and that the government is “beginning early plans for what we can do to make sure these stocks remain intact.”
But Hinch said there is little that can be done before the dam bursts.
“All we can do is hope that the temperatures these fish are in don’t do them irreversible damage for too long. And that the fish get to the Chilcotin when the river is ready to migrate.”
