December 6, 2023 — For newly hatched Western Alaska chum salmon, there is no time to waste when it comes to making their way to the open ocean. The tiny fry begin their journey from their natal streams just days or weeks after being born. When they finally reach the Bering Sea, sometime from mid-June to mid-July, their priority becomes consuming marine prey and building the energy reserves that will carry them through their first winter. Throughout their years in the ocean, the Western Alaska chum will travel extensively between the Bering Sea and the Gulf of Alaska.
Unfortunately, simultaneous warming trends in the Bering Sea and the gulf appear to have come as a double whammy for Western Alaska’s juvenile chum salmon. A new study by scientists from the National Oceanic and Atmospheric Administration (NOAA) and the Alaska Department of Fish and Game shows a possible link between a period of exceptionally warm ocean temperatures and chum crashes seen across Western Alaska.
“Loss of sea ice is having an impact on various ecosystems. And so with warming we’re seeing a change in the food web,” said Ed Farley, lead author of the study and head of NOAA Fisheries Ecosystem Monitoring and Assessment Program. “That food web is less energetic. It’s poorer-quality prey. And it’s impacting juvenile salmon, especially juvenile chum salmon in the northern Bering Sea. It’s impacting their fitness prior to winter.”
By “poorer-quality prey,” Farley primarily means jellyfish, also known as cnidaria. Jellyfish have been shown to proliferate when ocean temperatures warm.
“There are more cnidaria in the ecosystem of the Northern Bering Sea during warm years, but there was significantly more during this most recent anomalously warm period,” Farley said.