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Young Hatchery Coho Offer Hope and Research Opportunities at Redwood Creek

By Scientists in Parks Intern Brooke Harvey, San Francisco Bay Area Network Salmonid Monitoring Program
Two people standing calf-deep in Redwood Creek. One is gently lowering a blue bucket into the water, towards a tangle of woody debris.
San Francisco Bay Area Network and Golden Gate National Parks Conservancy staff release a bucketful of juvenile coho salmon into Redwood Creek on November 19, 2024.

NPS

Underwater photo of a half-dozen small, silvery fish swimming out of a half-submerged little blue net into a creek pool..
Biologists and volunteers released 3,000 tagged juvenile coho salmon from Warm Springs Hatchery into Redwood Creek.

NPS / Environment for the Americas / Cameron Huynh

December 2024 - For two weeks in October 2024, the San Francisco Bay Area Network (SFAN) fish crew travelled daily to Lake Sonoma’s Warm Springs Hatchery. There, we marked approximately 3,000 juvenile coho with PIT (passive integrated transponder) tags for release into Redwood Creek which flows through Muir Woods National Monument. This effort was time well spent, as these fish present unique research opportunities—as well as a chance to increase the future viability of the small wild population in Redwood Creek.

From the information we gathered during our surveys last July in Redwood Creek, only around 500 juveniles survived to late summer. This is far fewer than anticipated given how many spawners and redds the fish crew spotted during the 2023-2024 spawner season.

Three people at a long, plastic table inside a large, warehouse-like hatchery facility. They have buckets, a laptop, and various weighing and PIT tagging equipment arrayed in front of them.
Watershed Steward Program members Justin Jang and Valentin Kostelnik joined by Golden Gate intern Ruby Sainz measuring and tagging coho.

NPS / Brooke Harvey

Young woman gently holding a small fish upside down and touching her finger to its underside.
Sainz PIT tagging a young coho so it can be studied upon release.

NPS / Justin Jang

With such a small population remaining in Redwood Creek, the National Park Service and regional recovery managers from both California Department of Fish and Wildlife (CDFW) and NOAA’s National Marine Fisheries Service decided additional juvenile coho were needed to increase the future viability of this small population. This mission was a great fit for Warm Springs Hatchery. As a conservation hatchery, it aims for informed hatchery fish releases that result in successful adult coho spawning. Adding fish to Redwood Creek to augment the wild population should achieve that. The fall hatchery release should further help by increasing genetic diversity when the wild and hatchery fish return as 3-year-old adults to spawn during the winter of 2026-2027.

As a monitoring team, we also see this release as a dual opportunity. It'll let us test the success of this augmentation strategy and compare the survival of these fish to those released in the Russian River Broodstock Program. The information collected on this release group in Redwood Creek will help in deciding whether hatchery augmentation is worth the investment in following years or a new release strategy needs to be employed.

The juvenile release will also give SFAN and Warm Springs a better idea about how hatchery fish fitness compares to wild fish fitness (using growth rates) and how hatchery fish outmigration timing compares to that of wild fish.

People stand on the back of a pickup truck, using a large net and funnel to transfer fish to a blue bucket-backpack in front of a crowd of children and adults.
California Department of Fish and Game employees offloading coho into barrel backpacks and giving a demonstration to several education programs on the release day.

NPS / Point Reyes National Seashore Association / Gillian Campbell

After giving the tagged fish a few weeks to heal, we released them into Redwood Creek on Tuesday November 19, 2024. We were joined by Army Corps of Engineers staff from the hatchery as well as volunteers from Golden Gate National Recreation Area, Golden Gate National Parks Conservancy, and the CDFW. In teams of four, we worked our way up the creek and released juveniles in areas with suitable habitat (deep pools with woody debris cover) to give them the best chance of survival. When introducing juveniles, it’s important that the pool you are putting them in is attached to the mainstem and there is some sort of vegetation structure for protection from predators and high flow. We also made sure the pools we released fish into were spaced far enough apart to allow fish to naturally disperse without overcrowding any one area of the creek.

Four people with blue bucket backpacks and buckets set down beside Redwood Creek. They are scanning fish as they transfer them to the non-backpack bucket, and recording data on tablets as they go.
Team of four SFAN, PRNSA, and SPAWN staff recording PIT tag numbers on field tablets while releasing coho on Redwood Creek.

Golden Gate National Parks Conservancy / Michele Gee

With habitat restoration occurring in tandem with population-boosting efforts such as this, we hope to see higher returns of adult coho and successful spawning. Overall, the hatchery introduction was a major success, and we would like to thank everyone who came out to help and take part in the event!

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Logo text reads "SF Bay Area Inventory & Monitoring." Circular illustration of a scene combining distinctive rock formations, a redwood tree, and the Golden Gate Bridge over the SF Bay, each outlined in white. Illustrated binoculars overlap the

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Golden Gate National Recreation Area, Muir Woods National Monument

Last updated: April 9, 2025