Federal fisheries experts are painting a devastating picture of the challenges facing Pacific salmon and point to climate change as the main culprit.

A new report from Fisheries and Oceans Canada found warming ocean temperatures and marine heat waves are affecting ocean food webs and causing declining salmon stocks. Fisheries staff say factors such as human activity that degrades fish habitat and a landslide on the Fraser River blocking millions of fish from spawning upstream are making things worse.

Andrew Thompson, regional director for fisheries management, says it's been an extremely challenging year for salmon and there have been significant declines in a number of stocks.

In one of the most dramatic shifts, the federal Department of Fisheries has adjusted the estimated number of returning Fraser River sockeye to slightly more than 600,000, down from an earlier projection of nearly five million.

Sue Grant, head of a federal program on the state of salmon and author of the report, says some of the declines are residual effects of larger climate change events.

"Everything we're seeing in salmon and ecosystem trends is embedded within this larger context," she said, adding that Canada is warming at a rate double the global average and the rate increases at northern latitudes.

Sockeye salmon in the Adams River near Shuswap Lake, in B.C.'s southern Interior. (Chris Corday/CBC)

Less freshwater the better

But it is not just the climate impact on oceans that is stressing B.C. salmon.

Fresh water ecosystems are also feeling the brunt of climate change with more landslides and forest fires. That combines with human activity such as development and deforestation to hurt the health of these critical salmon habitats.

Grant said salmon that spend less time in freshwater, such as pink, chum, river-type sockeye and ocean-type chinook, are "generally doing well" and are not exhibiting long-term declines, suggesting they are less vulnerable to climate change.

According to the report, chinook, sockeye and coho numbers are declining throughout the province. Warming ocean temperatures enable less-nutritious zooplankton from southern latitudes to thrive in warmer northern waters. Zooplankton is a key food source for salmon

Federal Fisheries Minister Jonathan Wilkinson said that 2019 has been an especially difficult year in what has been a decades-long decline in stocks.

"There is no question that climate change is having a significant impact on our salmon," he said at a news conference Thursday. "Not only do these declines have direct impacts on our ecosystems and the health of our environment, but they have serious impacts on the health of our economy."

Shortly after a heatwave hit Alaska in July, locals along the Koyukuk River began reporting that dead chum salmon were washing up along the river banks. (Submitted by Stephanie Quinn-Davidson)

Protection recommended

Twelve out of 13 Fraser River chinook populations have been recommended for protection under the Species at Risk Act, while coho returns in Alaska and Skeena River sockeye returns also prompted significant fisheries closures.

Wilkinson also announced $2.7 million for five projects under the British Columbia Salmon Restoration and Innovation Fund.

"Part of any realistic plan to protect and ultimately restore key salmon stocks must include a comprehensive and aggressive plan to reduce carbon emissions," he said.

The report comes as workers continue to clear a landslide along the Fraser River that's blocking the migration route of millions of salmon on their way to spawning grounds.

"This is undoubtedly a crisis situation," Wilkinson said.

About 270,000 salmon have been recorded in the river below the barrier, while only 26,000 have been moved upstream, primarily via helicopter, he said.

A rock slide has constricted the Fraser River near Big Bar, just north of Lillooet. (Vincent Bryan/Whooshh Innovations)

'Stand up for our salmon'

The response effort is facing criticism.

Esk'etemc Chief Fred Robbins, whose community is upstream of the slide, said he is concerned that the fish that make it past the slide are too exhausted to continue on to spawning grounds.

"The impact of the rock slide is devastating. We had a community meeting where my whole community showed up, probably close to 250 people jammed into our gym and we talked about the impact," he said. "We need to stand up for our salmon."

Robbins interrupted Wilkinson's news conference alongside Chief Judy Wilson of the Union of B.C. Indian Chiefs to call on Ottawa and Victoria to declare a state of emergency on the Fraser River.

Pipeline protesters are silhouetted while carrying cutouts of salmon during a demonstration in Vancouver, B.C. (Darryl Dyck/The Canadian Press)

Wilson also questioned how the federal government could say it's committed to fighting climate change at the same time that it approved and bought the Trans Mountain pipeline expansion project, which comes with a sevenfold increase in tanker traffic.

Wilkinson said decisions about the slide response are made by members of a group that includes First Nations as well as provincial and federal officials.

Don Willimont, a director with the Spruce City Wildlife Association, said fisheries officials should have acted boldly when the Big Bar slide was first discovered.

Willimont said his groups have identified just 16 chinook in five Fraser River tributaries above the slide.

Just under 5,000 fish were counted in those tributaries in 2014 and those numbers were considered dire at that time, he said.

To learn about salmon and their importance for the survival of the southern resident killer whales check out the CBC podcast Killers: J pod on the Brink.