USA: Study points to concurrent marine heat waves as culprit in Western Alaska chum declines

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-warmer water temperatures that lingered in the 2014-2019 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 ...