Sockeye salmon spawning in B.C.'s Adams River in 2010.

Ocean warming may be factor in sockeye decline

Study ties salmon productivity drop to 'shared mechanisms'

Sockeye salmon along the west coast are producing far fewer returning offspring than in the past and the SFU fishery scientists who have documented the trend say it suggests climate change may be a factor.

Randall Peterman said the study he co-authored found 24 of 37 sockeye stocks from Washington State to Alaska lost productivity since 1985, with the hardest hit runs no longer even replacing themselves.

He said the fact the decline has been widespread across both pristine and heavily disturbed watersheds points to non-local “shared mechanisms” as the more probable cause, rather than river-specific logging or pollution.

“It’s much more likely that what’s causing these changes is occurring over a large area,” said Peterman, a professor in SFU’s School of Resource and Environmental Management.

Warming oceans could be reducing the salmon food supply in the north Pacific, sending more predators towards the sockeye or increasing their vulnerability to pathogens, he said.

The culprit could also be affecting sockeye in freshwater, Peterman added.

A pathogen – either naturally occurring or spread by fish farms – could be amplified by climate changes and infecting sockeye in rivers that later die at sea.

Preliminary findings were presented in 2011 to the Cohen Inquiry, which reports in the fall with recommendations on halting the decline in Fraser River sockeye.

But Peterman said the newest analysis shows the pattern of declining productivity has spread northward to more watersheds over time.

“That trend of spreading northward is indicative of possibly climate-driven processes that become more extreme in the south first and work their way north,” he said. “The evidence is much stronger than it was.”

The theory of a fish food shortage on the high seas is backed in part because sockeye have tended to return significantly underweight in recent years. The food supply is expected to decline as the ocean warms.

But Peterman noted increased competition for the same food supply is another possibility.

The number of pink salmon feeding in the same area of the north Pacific has more than doubled, largely the result of “ranching” of pinks by Russians and Alaskans.

“Because they feed on similar food to sockeye salmon there may be increased competition,” Peterman said.

The study was published in the Canadian Journal of Fisheries and Aquatic Sciences.

Just Posted

Comedy, chicken poop and dancing at Lytton Festival

This year’s festival will honour longtime supporter Shirley James

LETTER: Recreational angling has low-impact on Fraser salmon

Jason Tonelli writes about his displeasure at the call to close recreational fishing on the Fraser

Hope’s Wheeled Wild Women hit the road for cancer research

Group of friends ready for the 200-km bike trek that ends in Hope

PHOTOS: Paintings return to Kilby for fifth annual festival

The Plein Air Festival will be taking place at the historic site all weekend

Cougar spotted in Seabird Island

Residents are asked to report all sightings to conservation

Sts’ailes invites adults to become engaged in Halq’eméylem with new video series

‘Qw’oqwel te Qw’oqwel’ gives language learners an immersive way to learn Halq’eméylem

Advocates ‘internationalize’ the fight to free Raif Badawi from Saudi prison

Raif Badawi was arrested on June 17, 2012, and was later sentenced to 1,000 lashes and 10 years in jail for his online criticism of Saudi clerics

RCMP, search crews hunt for 4-year-old boy missing near Mackenzie

George went missing early Saturday afternoon

Canadian entrepreneurs turning beer byproduct into bread, cookies and profits

Some breweries turn to entrepreneurs looking to turn spent grain into treats for people and their pets

Canada ‘disappointed’ terror suspect’s British citizenship revoked

Jack Letts, who was dubbed “Jihadi Jack” by the U.K. media, has been detained in a Kurdish prison for about two years

Chrystia Freeland condemns violence in Hong Kong, backs right to peaceful assembly

There have been months of protests in the semi-autonomous region

B.C. VIEWS: Log exports and my other errors so far in 2019

Plastic bags, legislature overspending turn out differently

Most Read