For salmon stymied by B.C.'s Big Bar landslide, survival depends on help from above

In late June, fisheries officials learned of a landslide along the Fraser River near Lillooet, about 250 kilometres by road northeast of Vancouver. Rocks, some as big as cars, had sheared off a 125-metre cliff and lodged in the river, creating a five-metre waterfall below.

For wild salmon, it might as well have been a brick wall.

The Fraser River is a migratory path for five species of wild salmon, which return to fresh water from the ocean to spawn.

The fish are a food and cultural mainstay for First Nations, the backbone of B.C.’s sport and commercial fisheries, and essential food for other species, including endangered killer whales.

Even before the slide, Fraser River salmon were in trouble.

Chinook – big, powerful fish that are a dietary mainstay for killer whales – are at risk of disappearing. Federal assessments last year found 12 of 13 Fraser River chinook populations to be at risk. This year’s sockeye run has been dismal.

Harvests have been cancelled or restricted and, this month, labour and First Nations groups called for federal disaster relief for fishing-dependent communities.

So the slide could hardly have come at a worse time, or place.

As long-term questions rumbled – Could it have been detected sooner? What impact would it have on future runs? – the immediate focus was clear.

Save the fish.

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A tough spot

The Big Bar slide is at the foot of a cliff. Even assessing the site was a challenge. Before anybody could go about blasting or moving rocks to help fish get through, loose rock had to be removed from cliff walls.

Rock scalers tackled the wall with hand tools. Helicopters dumped water from giant buckets to sluice loose debris.

As of early September, an estimated 2,000 cubic metres, or 300 truckloads, had been removed.

The river flow is unpredictable, making basic tasks – such as installing sonar counters to see if any fish were making it upstream – a challenge.

In July, flooding on the Chilcotin River, north of the slide site, sent water and debris downstream.

Canyon walls form a wind tunnel and summer temperatures in the area can be scorching.

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The players

British Columbia did not declare a provincial state of emergency over the Big Bar landslide, as it did for wildfires in August, 2018. (The province ended that state the following month as weather cooled.)

But the approach to tackling the slide has had the hallmarks of emergency response, including a co-ordinated effort featuring federal and provincial governments, First Nations and multiple agencies, all working from a command centre in Lillooet.

There have been up to 180 people working on the response, ranging from hydrological engineers to helicopter pilots to wildfire service employees who carried flopping, slippery fish from nets to buckets for transport by helicopter.

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The options

To a layperson, it might seem simple: Blow up the slide so fish can get through. But the site had to be assessed, a helipad built. By early September, the team was still working on getting an excavator to the site.

Teams weighed the possibility of moving fish by helicopter, by truck or with a fish cannon, a device that would essentially shoot the fish over the slide.

The door was thrown open for advice. The U.S. Army Corps of Engineers was tapped for technical suggestions (the agency had little to add to what teams on the ground were already doing, officials said on a recent technical briefing). A suggestion from a Yinka Dene member resulted in a plan to ship up to 200 Early Stuart sockeye to a rearing facility in Chilliwack. (Early Stuarts, which migrate to the Stuart Lake system near Fort St. James, are one of the stocks flagged as “of concern” by federal authorities.)

Over the past couple of months, crews built a road for trucks. Helicopter transports began, shuttling fish caught using seining, dip-netting and a fish wheel, a system of buckets that turns with the river’s current.

Glitches were tackled as they happened. Cultural and archeological assessments were part of the process. As water levels dropped, workers were able to start moving rocks, using hand tools, small blasts and muscle to create new pathways for the fish.

The rock moving involved “lots of physical labour and lots of kind of playing chess," Sam Fougère, a senior engineering geologist with BGC Engineering, said in a Sept. 6 technical briefing.

“If we are not sure what is going on, we actually just look at what the fish are doing,” Mr. Fougère added. “Within minutes of doing work, they will either make passage through that section we are working on or they won’t. And we have to do additional work.”

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What’s next

In early September, the momentum appeared to shift. Salmon were swimming past the slide. The fish included pink salmon, which are smaller and weaker than chinook and sockeye that had been making their way past the obstacle.

In a Sept. 11 update, the incident command team said 160,000 fish had swum past the landslide since the response began.

Over the preceding six weeks, more than 60,000 salmon had been captured and flown by helicopter upstream of the landslide.

With monitoring showing that 85 per cent of salmon were making their way past the slide, the command team put transport operations on hold. If there are problems with pinks – about 800,000 are expected in coming weeks – transports could start up again.

The incident command team estimates it moved about a third of the chinook and a quarter of the sockeye that arrived below the slide between the time the response began in June and early September, when it was put on hold because most fish were getting through.

For some sockeye, the only spawners this year will be those moved by human crews.