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New research suggests 70% decline in diversity of BC sockeye over a century

CHAD PAWSON Feb 23, 2021

Scales from sockeye salmon harvested more than a century ago show the fish returning to the country’s second largest watershed for salmon are 70 per cent less diverse than they were in 1913, according to a new study from Simon Fraser University’s Michael Price.

Price, a PhD candidate in biological sciences, first undertook genetic testing two years ago of sockeye scales that have been collected since 1912 — before the introduction of motorized fishing boats on the river — to track how the abundance of sockeye salmon in the Skeena River had changed over time. He found declines of around 70 per cent.

Now he’s used even more of the fish scales, ones from 1913 to 1947, to show how the diversity of sockeye salmon returning to the Skeena River, which is the second largest producer of sockeye salmon after the Fraser River, has also seen a similar decline of around 70 per cent.

There are at least 13 genetically different sockeye salmon that spawn in the rivers or tributaries of the Skeena River watershed and that has not changed in 100 years, the study found.

However Price and co-author John Reynolds show that the vast majority of sockeye salmon now returning to the Skeena River to spawn, some 90 per cent, are of one type that originates in the Babine River, a tributary of the Skeena River.

Price says the predominant strain of sockeye in the Skeena River is wild — meaning fish that were not born in a hatchery or in a human-controlled spawning channel — which could affect the fish’s ability to thrive as climate change and other pressures on the fish progress.

“Diversity really is a barometer of resilience to provide the adaptive potential for the salmon to survive and thrive in an increasingly variable environment,” he said.

The research, done in conjunction with Fisheries and Oceans Canada, was published Monday in the Journal of Applied Ecology.

Price and Reynolds hope the new work will help with decision making in how to rebuild threatened salmon populations.

Sockeye salmon, known for their red hue when spawning, are a prized fish in commercial fisheries and are also important in the diets of marine mammals, bears and bald eagles.

Price said the reduction in sockeye diversity is a result of past fishing where selective gill-netting for larger fish was done, along with habitat degradation.

The study found hatcheries and controlled spawning channels have also contributed to a less diverse sockeye salmon population associated with the Skeena River watershed.

“This enhancement may increase abundances for some populations, but also can erode local diversity, homogenize life-history traits and further erode wild salmon abundances through competition in the ocean,” read the study.

Price says despite the decline in diversity, he still believes the fish have a future in B.C.

“Hope for me lies in the resilience of these animals,” he said. “They have persisted through changing climate over the last 10,000 years … they will persist in the future.”

Still, Price said that action is needed, such as limiting fisheries and restoring habitat, to help sockeye salmon stocks from deteriorating more.

“We are on the precipice of change,” he said.