The naturally occurring landslide in the Tahltan River occurred in early May. This is an image of the river taken by Fisheries and Oceans Canada staff in mid-June.
Canadian officials are airlifting Chinook and sockeye salmon over a landslide that caused a barrier to salmon passage in the Tahltan River, a tributary of the Stikine.
Steve Gotch, Fisheries and Oceans Canada (DFO) director for the Yukon and Northwestern British Columbia, said the landslide occurred about a half mile up the Tahltan on May 20.
The river is roughly 120 miles upstream of the Stikine, but the salmon that swim up it provide harvests for Southeast Alaskan and Canadian commercial and subsistence fishermen.
"Around 50 percent of the natural production of Chinook and sockeye comes out of this particular part of the drainage," Gotch said.
Because the area is inaccessible by road, DFO staff are being flown in by helicopter where they capture salmon downstream of the blockage and transport them around 10 miles upstream via a helicopter and bucket sling.
Since efforts began July 7, DFO staff have transported around 1,700 sockeye and 300 Chinook across the barrier.
"We're using a combination of dip nets, seine nets and some angling," Gotch said. "Those three techniques we've found are least disruptive and least injurious to the fish."
Gotch said around 25,000 sockeye and 3,500 Chinook salmon normally make their way up the Tahltan each year.
"That's the number of fish that are going to show up at the mouth," Gotch said. "The goal that we've set for ourselves is to move 10,000 fish. That will be a reasonable accomplishment. It's a fairly large number of fish to move."
Workers have been able to transport around 300 to 400 fish per day, Gotch said.
He added that DFO staff have also witnessed some salmon making it up the rapids and falls caused by the slide.
When water levels drop in the fall, DFO officials will begin exploring how to break up the slide debris. One option, Gotch said, is to use an explosive charge.
"The magnitude of the charge would be very small. It would involve controlled drilling into the rock materials within the channel and inserting some very small charges with the goal of trying to crack those larger rocks such that, during the spring flood flow, those rocks and material will get washed out and reestablish the flow of water through that area," Gotch said. "The bottom line is that we hope to undertake whatever remedial measures to re-establish passage for next year."
The salmon that DFO staff are transporting comprise a stock of fish that is governed under the Pacific Salmon Treaty- an international treaty between Canada and the U.S. whereby the two countries agree to cooperate in the management, research and enhancement of Pacific salmon stocks.
A similar event occurred in 1965 and a similar response was undertaken, Gotch said.
"It's not something that's uncommon in this area when you look at the geologic time scales," Gotch said.
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