In an effort to boost the population of spawning coho salmon in Marin County’s Redwood Creek, biologists from the California Department of Fish and Wildlife (CDFW) and the National Park Service (NPS) this week released nearly 200 adult coho salmon in the creek at Muir Beach.
The released coho salmon were collected as juveniles from Redwood Creek in the summer of 2015 at an age of six to eight months and reared to adulthood at the Warm Springs Fish Hatchery in Geyserville at the base of the Lake Sonoma Dam.
The release of coho salmon this winter is the culmination of the Redwood Creek Coho Salmon Rescue and Captive Rearing Project. This project, a collaborative effort by CDFW, NPS, the National Oceanic and Atmospheric Administration (NOAA) Fisheries, the U.S. Army Corps of Engineers and the California Department of Parks and Recreation, was initiated in 2014 with the goal of preventing the extinction of the coho salmon, which is listed as an endangered species under both the California Endangered Species Act and the federal Endangered Species Act.
Prior to 2014, fewer than 10 adult coho salmon were estimated to have returned to Redwood Creek annually to spawn. The long decline of coho salmon in Redwood Creek has been accelerated by recent periods of poor ocean survival combined with the prolonged California drought. Coho salmon are more sensitive to habitat degradation and poor water quality than other Pacific salmon species since they rear as juveniles in freshwater for a year or more.
Biologists hope that the released fish will migrate upstream and spawn in the creek. NPS monitoring staff will survey the creek in the summer of 2018 and collect tissue samples from juvenile fish. Genetic analysis of the tissue samples will indicate how many of the released adult fish produced viable offspring.
The first major release of adult coho salmon in Redwood Creek occurred in the winter of 2016. A third and final release of adult coho salmon is planned for the winter of 2018-19.
More information about the Redwood Creek Coho Salmon Rescue and Captive Rearing Project can be found on the CDFW website at wildlife.ca.gov/Drought/Projects/Redwood-Creek-Coho. The Redwood Creek coho restoration project is part of a broader effort to sustain and restore coho salmon runs along the central and northern California coast.