For the 2024-2025 spawning season, monitoring teams estimated more than 30,000 adult Central California Coast Coho salmon returned to Mendocino coast rivers, according to a NOAA Fisheries report on the record return. This doubles the previous record of 15,000 fish the season before, a stark change from a decade ago when only 3,000 fish annually returned. The species is listed as endangered under the US Endangered Species Act; NOAA Fisheries includes it in Species in the Spotlight, a program tracking nine especially imperiled species.
According to a NOAA report on restored habitat, rivers and streams were cut off from floodplains, and much of the watershed lacked stream structure after large redwood trees and fallen logs were removed over two centuries through logging and human activity. Young Coho salmon spend one to two years in freshwater and must survive dry summers when streams fragment into separate pools, and winter floods where they risk being swept to sea without slow-moving side channels.
How streams regained their structure
For Mendocino coast habitat restoration, the Office of Habitat Conservation awarded $14.5 million in 2023 from the Infrastructure Investment and Jobs Act to The Nature Conservancy and Trout Unlimited for multi-year projects. One example: Trout Unlimited removed a barrier in Neefus Gulch (a North Fork Navarro River tributary) in 2024, restoring 1,600 feet of stream and reopening spawning habitat upstream. In 2021, the organization had already removed another Neefus Gulch barrier. At the Dry-Dock crossing, NOAA-funded work replaced old road culverts with a ten-foot-wide, 68-foot-long aluminum crossing. In fall 2023, a seal-pursued steelhead passed through and Trout Unlimited monitors found a young Coho salmon above. Project lead Anna Halligan suspects fish may have had no upstream habitat access for 70 to 100 years. Planning and design took a decade.
Record return at Ten Mile River
Recovery is most dramatic at Ten Mile River. In spawning season 2023-2024, an estimated 5,574 Central California Coast Coho salmon returned, a record. That season, the river first exceeded NOAA's recovery goal of 3,700 fish. Species delisting could occur if upward trends persist across multiple watersheds, NOAA Fisheries says. The Nature Conservancy spent six years restoring winter habitat for juvenile salmon on the lower Ten Mile River. Project manager Peter van de Burgt reports heavy use of restoration sites where fish grow much faster, are fitter, and have better survival odds. Only 5 percent of historical winter salmon habitat remains available, van de Burgt says; historically it consisted of functioning wetlands and floodplains, now almost entirely gone.
More than one factor
Winter 2023-2024 brought 15,000 returning Coho salmon, the highest to date. Preliminary estimates suggest winter 2024-2025 saw that number nearly double. High Country News quotes Sarah Gallagher, who leads the California Department of Fish and Wildlife's monitoring program, citing restoration work plus favorable ocean conditions and a break in multi-year drought as jointly favorable factors for the strong Coho influx. Much restoration work and Gallagher's monitoring received support from NOAA's Pacific Coastal Salmon Recovery Fund.
Historical context
A 2012 monitoring study estimated 1,167 adult Coho salmon on the entire Mendocino coast over three years, with confidence intervals from 488 to 2,068 fish. By 2008, California's entire Coho population was estimated at 5,000 fish, just 1 percent of historical numbers. In winter 2024-2025, Mendocino County alone counted more than 30,000. In summer 2025, a water specialist with the Pinoleville Pomo Nation confirmed natural Coho reproduction in the upper Russian River for the first time since 1991, according to a California governor's announcement of December 11, 2025. At Jenner Headlands Reserve on the Sonoma coast, Coho were spotted for the first time in roughly 60 years the week that announcement came. California's Salmon Strategy includes 71 conservation measures; by summer 2026, 49 percent were complete and 51 percent had partial progress, according to a progress report.
A fraction of historical abundance
The recovering population remains a fraction of what it was. Historically, hundreds of thousands of Coho salmon returned annually to California rivers. Conservationists themselves urged caution, warning it is premature to judge current season numbers even though signs point to another strong year.