December 5, 2023 — Successive marine heat waves appear to have doomed much of the chum salmon swimming in the ocean waters off Alaska in the past year and probably account for the scarcities that have strained communities along Western Alaska rivers in recent years, a newly published study found.
In the much-higher water temperatures that lingered in the 2014-19 period, juvenile chum salmon metabolism was super-charged, meaning they needed more food, said the study, by scientists with the National Oceanic and Atmospheric Administration and the Alaska Department of Fish and Game. But the food that was available was of low quality — things like jellyfish instead of the fat-packed krill and other prey they normally eat, the study said.
That means for the juvenile salmon trying to survive their first year at sea, “there’s not much gas in the tank,” said the study’s lead author, Ed Farley, manager of NOAA Fisheries’ Alaska Ecosystem Monitoring and Assessment Program.
Juvenile chum salmon that swam from spawning areas in the rivers suffered what was essentially a double hit, said Farley, who works in the NOAA Fisheries Auke Bay Laboratories in Juneau. They encountered one extreme heat wave in their critical first summer when they were in the northern Bering Sea and then, when they entered their wintering grounds in the Gulf of Alaska, swam into the tail end of another extreme heat wave, he said.