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 branches and logs) that impact their survival and make them strong indicators of stream health and environmental change.
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. The National Park Service Inventory and Monitoring Program and its partners began monitoring coho and steelhead in Golden Gate National Recreation Area and Point Reyes National Seashore in 1998. The data collected by the Inventory and Monitoring Program is used to identify population trends and establish recovery goals, identify impaired park habitats, guide stream restoration and protection efforts, and prepare for the effects of climate change.