Published May 2, 2024 Fisheries biologists at the University of Alaska in Fairbanks meanwhile have collaborated with the Alaska Department of Fish and Game, NOAA Fisheries and the University of Washington in ongoing studies of the divergent responses of western Alaska salmon to the changing climate.
“The main point is looking at how these climate changes impact downturns in Chinook and chum salmon,” said Erik Schoen of the International Arctic Research Center at the University of Alaska in Fairbanks. He collaborated with five other researchers, including UAF colleague Peter Westley and Schindler on this study.
Their report, released in the late summer 2023 in Fisheries Magazine, focuses on four major points:
Western Alaska salmon abundance reached historic extremes during 2021-22, with record lows for Chinook and chum salmon and record highs for sockeye salmon.
Salmon are maturing at smaller sizes. Since the 1970s, Yukon River Chinook salmon have decreased an estimated 6% in mean adult body length and 15% in fecundity, likely exacerbating population declines.
Salmon population declines have led to fishery closures, worsened user conflicts and had profound cultural and food security impacts in Indigenous communities that have been tied to salmon for millennia.
Changes in abundance and size are associated with climate changes in freshwater and marine ecosystems and competition in the ocean. Changes in predators, food supply and disease are also likely important drivers.
The study notes that waters in Western and Interior Alaska are warming nearly four times faster than the global average and twice as fast as waters in the continental U.S., with the impact of the Pacific Marine Heatwave of 2014–2016, the Pacific Marine Heatwave of 2019 and an air temperature heatwave and drought in 2019.
This warming is believed to have negatively impacted Chinook salmon, which would represent a fundamental departure from previous decades of salmon ecology research, which consistently found that warmer conditions improved salmon production in northern regions.
Changes in growth and age of maturity of western Alaska Chinook salmon have been linked to changes in ocean climate, and selective predation of larger individuals also may be contributing to accelerated maturation, the study said.
Chinook populations in the area are influenced by changes in demographics and food webs and are susceptible to bycatch and interception in other fisheries, researchers said, including the Arctic-Yukon Kuskokwim (AYK).
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