Most Pacific Coast salmon and steelhead stocks listed under the federal Endangered Species Act have increased in abundance over a 25-year span, but most still remain far under their recovery goals, according to a recent study by NOAA Fisheries scientists.
The scientists found that a majority of 28 distinct population segments of Northwest and California salmon and steelhead that were listed under the ESA from 1989 to 2007 and protected as threatened or endangered increased in abundance. None of the groups became extinct and groups protected by the ESA increased in abundance faster than unprotected populations of the same species, the study says.
During the 25 years studied (1995 to 2020), considerable efforts had been made to recover these populations, the study says, but no distinct population segment (DPS) has increased sufficiently to be delisted. A DPS represents specific geographic areas and genetic characteristics and are the smallest units that can be listed under the ESA.
“At the time of the salmon listings, there was a path toward recovery and a path toward extinction,” said Michael Ford, lead author of the research published in Fish and Fisheries. Ford recently retired as a research scientist at NOAA’s Northwest Fisheries Science Center. “So far, we have avoided extinction and even succeeded in moving many populations in the right direction, but most are still far from complete recovery.”
Geographically, over the 25-year study period, ESA-listed populations in the Northwest trended to be higher in abundance than those in California, likely because California salmon are closer to the southern edge of their range and exposed to greater climate stress, the study says. Of the protected populations, Chinook, chum and sockeye trended higher than coho salmon and steelhead.
For most DPS, whether listed or unlisted, trends in harvest rates and hatchery releases were relatively stable during the 25-year time period. However, trends in indicators related to freshwater and marine climate were generally negative for salmon.
“Our results suggest that salmon recovery actions may have helped to stabilize and increase protected DPS, but most remain far below their recovery goals,” the study says.
The study, “Abundance Trends of Pacific Salmon During a Quarter Century of ESA Protection,” was published in Fish and Fisheries (Abundance Trends of Pacific Salmon During a Quarter Century of ESA Protection – Ford – 2025 – Fish and Fisheries – Wiley Online Library).
Authors are Steven Lindley, Brian Spence, David Brouton, Heidi Fish, Michael O’Farrell, Nathan Mantua, Rachel Johnson, William Satterthwaite and Thomas Williams of the Southwest Fisheries Science Center, LA Jolla, CA; Ford, Katie Barnas, Andrew Shelton, Laurie Weitkamp, Damon Holzer, Elizabeth Holmes, James Myers, Chris Jordan, Martin Liermann of the Northwest Fisheries Science Center, Seattle, WA.
The scientists noted that West Coast states’ populations had grown by nearly 10 million people during the same 25-year period, adding pressure on water use and other resources. In addition, with a changing climate, stream flows are dropping while stream temperatures are rising.
“The findings suggest that the region’s focus on improving habitat and involving communities in salmon recovery has proved successful,” the study says.
However, that success has its limits. The study found that for most salmon and steelhead populations, “the road leading to increasing abundance and recovery has not been travelled very far. To be sure, abundance increases in a few DPS have been dramatic.”
Examples of success are a higher abundance for threatened Snake River fall Chinook, endangered Snake River sockeye and unlisted Okanogan River sockeye. All increased more than 10-fold in abundance from 2016 to 2020 over their abundances between 1995 to 1999. Snake River fall Chinook had been at an extremely low abundance in the mid-1990s, “a factor clearly contributing to some of the positive trends.”
Some of the increases in abundance were uneven, the study says. Coastwide, only five steelhead DPS increased (four listed, one unlisted), whereas nine decreased. Considering all species, eight of the 10 DPS in California had declining trends, and trends for Chinook and steelhead were correlated with latitude coastwide (i.e. lower abundance in California streams).
The study concludes that the listed population groups have yet to recover to the point where they no longer need protection even though, some – Snake River fall-run Chinook, Hood Canal summer chum and Oregon Coast coho – have increased “dramatically” since their listing.
“These trends indicate that these listed population groups are on the path to recovery. Recovering salmon populations to self-sustaining levels is critical to restoring the great economic and environmental benefits they once provided, when millions surged up West Coast rivers every year,” a NOAA press release says.
The scientists also looked at the impacts of hatchery releases and harvest on abundance of salmon and steelhead, noting that over 100 million juvenile salmon are released from West Coast hatcheries every year and most are harvested or return to their hatchery of origin. These fish, the study says, are not counted toward ESA recovery goals. However, some hatchery fish spawn in streams and are included in spawner counts that NOAA uses in its abundance trends. Their presence on spawning grounds can provide benefits to natural population conservation, as well as ecological and genetic risks, the study says.
The study also found that harvest rates were generally lower on listed population groups than on unlisted groups. Hatchery releases support commercial, tribal and sport fisheries and some from conservation hatcheries also help restore naturally spawning populations of threatened and endangered population groups, such as increases in the abundance of Snake River fall Chinook.
However, hatchery fish can also undermine natural populations by diluting the adaptations that help them survive. Nearly all listed population groups retain at least some populations made up mostly of naturally spawning fish that remain free of hatchery influences, the research found.
Some threats to salmon and steelhead persisted and increased during the study period, the study says. They are:
— Predation by marine mammals (pinnipeds, such as sea lions);
— Reduced stream flows and snowpack levels; and
— Increasing stream temperatures.
Still, the researchers say, they saw increases in many salmon population groups despite these trends and that shows that “local salmon recovery efforts have improved local conditions for salmon.” They also confirmed that changing ocean conditions impact the survival of adult salmon.
The research demonstrates that protection under the Endangered Species Act combined with investments in restoration can turn declining salmon population groups around, Steve Lindley, co-author of the research who recently retired as research scientist at NOAA’s Southwest Fisheries Science Center, said in NOAA’s press release. However, he said, “It takes time to reverse the accumulated damage to salmon habitats, and progress can be prevented or temporarily reversed by prolonged periods of poor environmental conditions, such as with populations in California that have experienced severe droughts in the last decade.”
For background, see:
— CBB, December 15, 2024, NOAA Status Review Of Four Northern California/Southern Oregon Salmon/Steelhead Species Says All Should Remain ESA-Listed, NOAA Status Review Of Four Northern California/Southern Oregon Salmon/Steelhead Species Says All Should Remain ESA-Listed – Columbia Basin Bulletin
— CBB, February 23, 2024, NOAA Status Review Says Sacramento Winter-Run Chinook Remain Endangered, Serious Threats From Climate Change, Disease, NOAA Status Review Says Sacramento Winter-Run Chinook Remain Endangered, Serious Threats From Climate Change, Disease – Columbia Basin Bulletin
— CBB, February 17, 2023, NOAA Fisheries To Conduct Status Review Of Olympic Peninsula Wild Steelhead To Determine If ESA Listing Warranted, https://columbiabasinbulletin.org/noaa-fisheries-to-conduct-status-review-of-olympic-peninsula-wild-steelhead-to-determine-if-esa-listing-warranted/
— CBB, June 2, 2016, NOAA Status Review: None Of 28 ESA-Listed Pacific Salmon/Steelhead Stocks Warrant Status Change, NOAA Status Review: None Of 28 ESA-Listed Pacific Salmon/Steelhead Stocks Warrant Status Change – Columbia Basin Bulletin