Adult sockeye salmon. Credit: Masahide Kaeriyama, Hokkaido University/NOAA Fisheries

Influence of Climate on Young Salmon Provides Clues to Future of World’s Largest Sockeye Run

UNITED STATES
Friday, April 12, 2024, 07:00 (GMT + 9)

The following is an excerpt from an article published by NOAA Fisheries:

New insight on how climate drives salmon survival provides key information for sustainable management and resilient fishing communities

The world’s largest run of sockeye salmon begins in Bristol Bay river systems that flow into the Bering Sea. There young salmon face a crucial bottleneck: they must find good food and conditions so they can store enough fat to survive their first winter at sea. Understanding how climate drives survival during this critical life stage is key to predicting future salmon returns in a rapidly changing ecosystem.   

A new study explores how climate influences survival of salmon—both directly through temperature, and indirectly through cascading effects on their food. Researchers looked at shifts in distribution and abundance of juvenile sockeye salmon in the Bering Sea in relation to temperature, prey, and competitors. The 17-year study (2002–2018) encompassed warm and cool conditions. The findings will help scientists more accurately predict future change to inform sustainable management and help fishing communities prepare for the future.

“Understanding how young salmon and their prey responded to past ecosystem change gives us a clue to what will happen in the future,” said study leader Ellen Yasumiishi, NOAA Fisheries biologist, Alaska Fisheries Science Center. “We want to know what’s driving the number of salmon returns so we can give fishermen an early outlook on what to expect.”

Juvenile sockeye salmon. Credit: NOAA Fisheries.

Salmon in a Warming Bering Sea

Climate change is rapidly and dramatically transforming the Bering Sea ecosystem. As the ocean warms, many marine species are on the move, seeking suitable habitat. Bristol Bay sockeye salmon, at the northern reach of the species’ range, have flourished with recent warming.

Pacific salmon such as sockeye support important commercial, subsistence, and recreational fisheries in Alaska. They play an important role in local culture and a complex role in the ecosystem. Predicting future climate-driven change is critical for developing sustainable management plans and helping fishing communities prepare for the future.

The eastern Bering Sea is an important nursery ground for juvenile Bristol Bay sockeye salmon. To predict how climate change may affect Bristol Bay salmon runs in the future, we need to understand how climate drives survival of young salmon during their critical first summer in the Bering Sea.  

Previous studies show that since 2000, young sockeye salmon abundance has increased in the Bering Sea. They moved to the north and west, and their diets differed between warm and cold years. 

“To understand how Bristol Bay sockeye salmon may respond to future climate change, we need to understand the mechanisms by which climate impacts them,” Yasumiishi said. “We need to know why their distribution, abundance, and diet shifted.”

Summer air temperature anomaly at St. Paul Airport in the southeastern Bering Sea, north Pacific Ocean, 2002–2018. Cool years are shown in blue, warm years in red.

Tracking Climate-Driven Shifts in Salmon and Prey

Researchers from NOAA Fisheries Alaska Fisheries Science Center and University of Alaska Fairbanks collaborated to begin to answer these questions. 

Study data were collected during Alaska Fisheries Science Center Bering Arctic Subarctic Integrated Surveys. These surveys took place in late summer in the eastern Bering Sea. The sampling period covered years of relatively warm (2002–2005), cool (2006–2013), warm (2014–2018), and exceptionally warm (2016) ocean conditions. This period of warm-cool-warm stanzas offered the opportunity to see how salmon and prey responded to various climate conditions.

Map of sampling locations in the southeastern Bering Sea.

Across these years, the team compared the distribution and abundance of juvenile sockeye salmon in relation to prey, competitors, and sea surface temperature. They also examined diets of juvenile sockeye salmon.

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Source: Alaska Fisheries Science Center  | Read the article in full by clicking the link here 

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