Article

San Francisco Bay Area Coho Salmon & Steelhead Trout Monitoring

Golden Gate National Recreation Area, Muir Woods National Monument, Point Reyes National Seashore

Federally endangered coho salmon juvenile.

NPS / Jessica Weinberg McClosky

Simple map of 3-4 branched stream systems in Golden Gate and Point Reyes. The smallest is Redwood Creek in the Muir Beach/Muir Woods area. Larger systems are in southeastern Point Reyes and the north district of Golden Gate.

Why Are Coho & Steelhead Important?

Federally endangered coho salmon and threatened steelhead trout are large, charismatic fish that play crucial roles in both stream and ocean ecosystems. They transport nutrients, help keep insect populations under control, and serve as food for larger fish and mammals. They also have many known habitat requirements (e.g. cool streams with unobstructed flow, good water quality, gravel beds and plenty of large debris) that impact their survival and make them strong indicators of stream health and environmental change. The National Park Service Inventory and Monitoring Program and its partners began monitoring coho and steelhead in Golden Gate National Recreation Area, Muir Woods, and Point Reyes National Seashore in 1998.

Large, olive-colored fish with small black spots, swimming against the current over a rocky creek bed. — An adult female coho spawning in Redwood Creek. Unlike steelhead which can make repeated spawning trips, coho perish in the creeks after their first spawning run. Coho and steelhead carcasses are one of the few sources of marine derived nutrients in coastal stream and terrestrial ecosystems.
NPS / Jessica Weinberg McClosky

Why Do We Monitor Coho & Steelhead?

To detect trends in the distribution and abundance of coho and steelhead at key life stages in creeks known to have coho, the species of primary concern
To determine trends in fish fitness (e.g. length, weight) at key life stages
To identify changes in coho and steelhead habitat

How Do We Use the Monitoring Data?

To identify impaired park habitats that hinder coho and steelhead recovery
To guide and evaluate stream habitat restoration and protection efforts
To predict and prepare for the effects of climate change, such as changing rainfall patterns, on stream habitats and associated fish populations

National Park Service biologist and volunteer sitting on buckets, one taking a fish to measure and weigh, the other recording data on a clipboard. — National Park Service staff and volunteers collect data on a coho smolt--a year-old fish undergoing the physical changes that will enable it to survive as it migrates out to the ocean to grow and mature.
NPS / Jessica Weinberg McClosky

What Have We Learned?

Both coho and steelhead populations have declined dramatically as a result of habitat loss, overfishing and changing ocean conditions. Spawning Central California Coast coho populations are down to only about 1% of historic levels. Because the coho have a unique life cycle where adults are normally three years old when they spawn, adults in the creek one year aren’t descendants of adults that were in the creek the previous year, or the year before that. They are offspring of adults from three years prior. This means that there are three distinct coho “cohorts” monitored at each creek. Specific trends vary by cohort and by creek, but in general coho on the West Coast are still in need of recovery actions.