A potentially catastrophic collapse of the sockeye salmon run is unfolding on the Columbia River system this year.

Scientists once predicted that about 100,000 sockeye would return to spawning grounds in the rivers and streams in British Columbia's South Okanagan region.

In fact, it was supposed to be one of the largest sockeye runs in recent history, said Okanagan Nation Alliance fish biologist Richard Bussanich.

Drought conditions stress sockeye

But Bussanich said the latest projection falls short of earlier expectations. Instead, it's now thought that a range of 18,000 to 47,000 will return to the spawning grounds this year. He said higher water temperatures and low water levels are stressing the migrating salmon.

"Fish are showing signs of physical stress," Bussanich said. "So there are open wounds and fungi and other things. The conditions are harsher than normal."

He said more than half of the sockeye on the Columbia have died.

"This is shaping up to be catastrophic for this year. And hopefully we don't have repeat years because then we will be into major conservation concerns."

Authorities have cancelled recreational and commercial sockeye fisheries on Osoyoos Lake.

In normal seasons, the sockeye fishery contributes up to $400,000 to the local economy.