Simon Fraser University


Averting a perfect storm for wild salmon

December 16, 2010

Despite this summer’s record sockeye salmon run, SFU scientists say a population explosion of hatchery and wild salmon in the North Pacific Ocean is leading hatchery fish to beat out their wild cousins for food.

In a new paper in Marine and Coastal Fisheries, four researchers, including Randall Peterman and Brigitte Dorner in the Faculty of Environment, predict a perfect storm is evolving that could seriously reduce wild salmon populations.

Peterman, a Canada Research Chair in fisheries risk-assessment and management, says stressors such as overharvesting and poor environmental conditions are reducing many individual North Pacific salmon populations.

But he says “the sum of both wild and hatchery pink, chum and sockeye salmon across all populations from all regions of the North Pacific is now the highest that has ever been recorded… likely due to favourable ocean conditions.”

Peterman and the paper’s other co-authors say the population explosion causes hatchery and wild salmon to compete for scarce, unpredictable food supplies—a fight the more prolific hatchery fish could easily win.

“The ocean is always changing, and current favourable ecological conditions for salmon will not last indefinitely,” says Peterman.

“Unless international agreements are developed to manage hatchery production levels across nations, hatchery salmon may dominate in the North Pacific, when ocean conditions deteriorate.”

The co-authors warn that the dominance of hatchery salmon would decrease not only wild salmon abundance but also their biological diversity.

“Higher levels of hatchery fish straying onto spawning grounds, combined with low numbers of wild fish, could further erode wild salmon diversity, which helps stabilize their abundances,” says Peterman.