Study: Most Pacific Salmon Populations Crashing (Except Bristol Bay); Ocean Temps May Be Key
EDIDT
But the sockeye salmon in Bristol Bay, which power the area’s $2 billion commercial fishing industry, remainan exception. The returns here have been increasing to record levels and are projected to surpass more than 70 million sockeye this year. Climate change is probably driving these changes as well. Unlike many salmon, Bristol Bay sockeye live in inland lakes for a time before venturing into the ocean. Those warming lakes are probably producing more food for the young salmon, according to biologists, helping prepare them for life on the high seas.
Salmon populations tend to travel to different parts of the Pacific. Many Bristol Bay sockeye spend their winters south of the Aleutian islands, where surveys more than a decade ago showed they were feeding well. But the Russian ship won’t travel to that area during the expedition this year. The recent extreme decline of western Alaska chum salmon, particularly those returning to the Yukon and Kuskokwim rivers, represents an urgent mystery fisheries scientists want to solve. Alaskans have pointed to fishing pressure — including salmon taken as bycatch by other ocean-going vessels — as well as competition from hatchery-raised fish, as possible factors in the Yukon salmon collapse.
Farley said the mass of warmer Pacific water, which slowly moved north into the Bering Sea, likely made it more difficult for these chum, particularly early in their lives, and is probably a main reason they died in great numbers. “If you’re a juvenile salmon and you’re spending your first year in the ocean, one thing you want to do is you want to grow,” he said. “We can see that these juvenile chum salmon did not put on a lot of fat prior to winter.”
Climate modeling suggests marine heat waves will occur more often as atmosphere and the oceans continue to warm. Salmon in the Pacific are still a “survival story,” Farley said. But these dramatic crashes in salmon populations are an ominous sign. Climate change, in his opinion, “drove a lot of the mortality that we’re seeing.”
EDIT
https://www.washingtonpost.com/climate-environment/2022/03/28/salmon-alaska-climate-change/