A group of environmental nonprofits filed a petition in 2022 to protect the spring-run Chinook along the Oregon Coast and part of Northern California.
Jeff Miller from the Center for Biological Diversity said spring-run Chinook are more threatened by habitat changes than fish that return in the fall.
"Spring-run are blocked in their migration to where they ideally want to go," Miller said. "A lot of their former spawning habitat is blocked above major dams."
Spring-run Chinook return from the ocean much earlier than the fall-run salmon and will stay in deep-water pools until the fall, when they head further upstream to spawn. That means spring-run Chinook often spawn further upstream than fall-run.
The National Marine Fisheries Service said that spring-run Chinook faced greater threats, including rising stream temperatures and habitat loss. But, the agency refused to split the spring- and fall-run populations into two distinct groups.
"Factors leading to this conclusion included the lack of spring-run specific habitat in most of the river systems in the ESU [environmentally significant unit] and the lack of strong evidence that the spring run was ever historically a substantial component of the ESU," the agency said in its decision.
The nonprofits initially sought only to protect the spring-run Chinook. But because the government would not split up the two populations, the groups had to petition for an endangered species listing that included both spring- and fall-run salmon.
Despite threats to spring-run salmon, the agency said fall-run salmon are more abundant and outweigh the threat to the overall population.
The federal government has only listed spring- and fall-run Chinook salmon separately for inland populations, not for salmon populations along the coast.
Miller said recent studies have found major genetic differences between the two populations, which justifies protecting just the spring-run salmon.
"These fish didn't evolve from fall-run Chinook," he said. "They evolved separately on their own, and they diverged a very, very long time ago. So they're it's really an irreplaceable run of fish that we would not get back if we just continue to say, 'Well, everything's fine.'"
Miller said his organization is looking at challenging the decision and possibly seeking state-level protections.
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This story comes to you from the Northwest News Network, a collaboration between public media organizations in Oregon and Washington.
