Huge sockeye run a mystery, not a trend, scientists say

Randy Shore
September 15, 2010
The Vancouver Sun

Scientists studying a 20-year decline in the Fraser River sockeye run say this year's miraculous abundance of fish is likely a blip and not a sign the fishery's problems are over.

Sockeye face myriad threats during their four-year life cycle, from food shortages, hungry sea lions and toxic algae to viruses, bacteria and sea lice, according to Simon Fraser University Prof. Randall Peterman.

Peterman is chairman of a panel of 11 experts from the U.S. and Canada assembled by the Pacific Salmon Commission to probe the available data on the decline of the Fraser River sockeye. The panel's report was released last week.

For this year's sockeye run, "all the different sources of mortality lined up to be favour-able at every life stage of the fish," Peterman said.

"Predation mortality, pathogens, starvation, all these things seem not to have been very important for the return this year. It was miraculously positive."

During the 1970s and 1980s, for every fish that spawned in the river, about six adult fish would return four years later. In recent years, after 20 years of steady decline, the number of fish returning for each spawner has dropped below one, culminating in 2009 when only 1.5 million sockeye returned despite predictions that 11 million fish would enter the river.

This year, 34 million sockeye returned to the Fraser.

"This year, productivity levels returned to about seven adults per spawner," Peterman said. "That's a dramatic turnaround, but one point does not make a trend."

Read the full story in the Vancouver Sun

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