British Columbia

Work at Big Bar slide site means Fraser River salmon should have better chance this year

The nature-like fishway has been improved but the "salmon cannon" is gone as officials continue work on restoring critical salmon passage past the slide site.

It's been 2 years since the discovery of major landslide that blocked the Fraser River to migrating salmon

A view from across the river gives a sense of the challenging terrain crews have been working in to re-establish fish passage at the slide site. (Submitted by the Fisheries and Oceans Canada)

On the two-year anniversary of the discovery of the massive Big Bar landslide on the Fraser River, officials say they are seeing some success in remediating the devastation caused to the river's native salmon.

Most notably, the widening of the man-made "nature-like fishway" to give salmon a swimmable route past the slide is expected to increase the number of fish that make it to their spawning grounds. 

"We have significant hope the nature-like fishway will manage most of the fish trying to get through the slide area, particularly the later-arriving large runs of salmon," said Michael Crowe, manager with the Big Bar landslide response team.

"Based on work to date ... we have high confidence most of those can get through relatively unimpeded and therefore be able to spawn effectively."

The Big Bar slide dropped 75,000 cubic metres of rock into the Fraser River north of Lillooet, creating a five-metre-high waterfall that blocked spawning sockeye and Chinook from the upper reaches of the largest salmon-bearing watershed in the province.

Aerial view of the man-made nature-like fishway that will help salmon swim past the Big Bar slide by slowing raging waters and providing places to rest. (submitted by Peter Kiewit Sons)

The slide is believed to have happened on Nov. 1, 2018, but wasn't detected until late in June 2019 because of the remote location.

The fishway was built near the river bank by strategically placing boulders in a pattern to slow the surging water and give salmon places to rest as they move upstream past the slide.

"What this allows fish to do is move from boulder to boulder, tuck in, and then dart to the next eddy," said Crowe.

Sprinting salmon need rest

"[Salmon] have a burst speed but they can only basically sprint for a short period of time before they have to rest. And you cannot have [water] velocities that exceed their burst speed because then the fish cannot move forward."

The work done this year to widen the fishway has made it passable at a greater variety of water levels, meaning more salmon will be able to use it this year compared to last, when an estimated 160,000 salmon swam through it in July and August.

Improvements have also been made to the truck and transport system, where salmon come up a newly constructed fish ladder into a holding tank and are then put on a truck, driven around the slide and released on the other side. 

The improved truck and transport system means the salmon being trucked around the slide site will no longer be handled by humans. (submitted by Fisheries and Oceans Canada)

Truck and transport is used later in the season when low river levels make the fishway unpassable.

According to Crowe, the new system will improve survival because it doesn't require direct human-salmon interaction. 

"Fish respond very poorly to handling and stress ... and it can severely impact migration success," he said. 

Salmon cannon gone

The much-reported-on Whooshh pneumatic tube system — also known as the "salmon cannon" — is no longer being used at the site. 

Gwil Roberts, director of the Big Bar landslide response, said although it worked, there were many challenges that made it uneconomical. 

Radio tagging is one way officials are tracking salmon movement past the Big Bar slide site. (submitted by Fisheries and Oceans Canada)

According to Roberts, $131 million has been spent so far on the various efforts to restore salmon passage at Big Bar. 

Crowe said only 25,000 chinook salmon are expected to return to the Fraser River this year and just 18,000 of the struggling early Stuart sockeye. Later runs of sockeye are projected at over one million.

Last year's return was estimated at just 293,000 by the Pacific Salmon Commission, the lowest return on record. Less than a decade ago, the average return on the Fraser River was close to 10 million salmon a year.

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