The largest-ever survey of the salmon ecosystem in the North Pacific Ocean brings together 60 scientists from five countries and a flotilla of four research vessels to learn about increasingly extreme climate variability and its effects on salmon survival.

The $10 million (€8.8 million) research effort was organized as part of the International Year of the Salmon, a project supported by the North Pacific Anadromous Fish Commission, a treaty organization comprising the United States, Canada, Russia, Japan and South Korea which was originally created to control driftnets on the high seas for salmon. The 2022 Deep Sea Winter Pan-Pacific Expedition will conduct detailed sampling, using the four research vessels to scan areas 60 nautical miles apart on the high seas. Researchers hope the sea scan can explain the fluctuations salmon populations in response to large variations in ocean temperature and better predict the future of key salmon spawning populations affected by climate change.

A NOAA research vessel, the Bell M. Shimada, will head out of Port Angeles, Washington, United States, on Tuesday, February 1, to begin its survey trajectory between the 47th parallel south of Seattle to north of Kodiak Island, followed by Canadian and Russian ships. vessels departing to cover other salmon study areas – up to 800 miles offshore.

According to Laurie Weitkamp, ​​a fisheries research biologist at the NMFS Northwest Fisheries Science Center, who leads the first leg of the Shimada’s research cruise, salmon spend most of their lives – five to six years – in the ocean before to swim in freshwater rivers for spawning. .

“It’s also the one [life phase] we know the least,” Weitkamp said. “When they go out into the ocean, they go into a kind of black box.”

After young salmon head to the ocean in late summer, winter is the second critical period in their lives as they are mobbed by predators and in search of food. Weitkamp said the most recent survey, completed in 2019, pointed to a difficult future for chum salmon.

“We saw a lot of really, really skinny chum salmon. They looked like they were starving,” she said.

According to Ed Farley, a biologist at the NMFS Alaska Fisheries Science Center in Juneau, years of sharp fluctuations in ocean temperature have had uneven effects on salmon stocks. In the 2021 season, there was a slump in chum salmon returns to the Yukon River, but Bristol Bay sockeye returns are at record highs. These fish spend their years at sea in different regions: Yukon River chum are found in the Gulf of Alaska, while Bristol Bay sockeye salmon are found south of the Aleutians and farther west, said Farley.

“That’s why these winter surveys are so important,” he said.

According to biologists, the biggest threat to salmon populations around the world is climate change.

The 2015 warm water “drip” and ocean heat waves that disrupted North Pacific fisheries are suspected to be the triggers for fluctuations in salmon spawning returns. The four research vessels involved in the project will collect data on ocean conditions and study the food web by conducting hour-long sampling trawl tows at 155 stations approximately 60 nautical miles off the northwest United States. to the end of the Aleutian Islands chain.

Scientists on board will collect genetic samples from captured fish, hoping to link those found at sea to fish swimming in spawning rivers. An autonomous underwater glider vehicle, controlled from the University of Alaska in Fairbanks, will follow the route of the Shimada, diving beyond 600 feet to record and transmit oceanographic data.

“This is probably the most daring and in-depth study of the North Pacific Ocean that has ever taken place,” Mark Saunders, an expedition organizer for the International Year of the Salmon, said during the conference. a conference call on January 28 with news. journalists.

“[With] climate change we are seeing now, the impacts are severe,” Saunders said. “‘Now is really the time to start understanding this.”

Research vessels will take samples to measure environmental and ecosystem influences ranging from plankton to top predators like salmon sharks. A Canadian commercial vessel will use gillnets to evaluate the effectiveness of large trawls in accurately measuring fish populations, particularly regarding the composition of salmon and rainbow trout in surface waters. Genetic sampling will be used to link fish found at sea to spawning populations in North Pacific rivers.

“If we can understand where these fish are in the deep sea, we can begin to link them to understanding freshwater management systems and actions that will need to know what the potential fate of these animals is in a changing climate system.” , Saunders said. .

And analysis of genetic samples that scientists collect at sea will be key to linking salmon caught at sea to the rivers where they spawn, according to Weitkamp.

“We can take a little fin clip and know exactly where it came from,” Weitkamp said.

In total, the effort involves 10 government agencies and the British Columbia Salmon Restoration and Innovation Fund. Tracks and reports from research vessels, as well as photos, videos and notes from expedition researchers, will be posted publicly on International Year of the Salmon website. The last of the expedition’s cruises will end in April 2022 and final reports will be released in May, with preliminary results being released at a symposium in Vancouver, Canada in October 2022.

Reporting by Kirk Moore

Photo courtesy of NOAA