Migrating between freshwater and marine ecosystems, salmon remain both ecologically and culturally significant to indigenous communities . Having a three-year life span, Coho populations are monitored using three separate cohorts where each cohort follows the life cycle of a single generation. The anadromous life cycle of these species begins with multiple stages in streams  where adults return to spawn after spending 1 to 3 years in the open sea. Spawning adults lay eggs in small depressions made by the upstroke of a female salmon’s body and tail which is known as a redd. Post reproduction, Pacific salmon remain in freshwater and die shortly after, and the decomposing body provides nutrients for the surrounding ecosystem.  

With this migration process, both freshwater and marine conditions must be suitable for survival. The National Park Service manages eggs and juveniles in multiple breeding streams. Survival and growth at these stages are influenced by many factors, such as loose gravel, cool water temperatures, and adequate stream levels that contribute to a healthy salmonid habitat. Due to this complexity, SFAN considers population counts at multiple life stages for this species to be a key indicator in determining local stream and ecosystem health. Since the implementation of current monitoring protocols over 12 years ago, there have been numerous advancements made in data collection technology and statistical techniques. IWS will be evaluating how effective current methods are at determining abundance and long-term population trends for each life stage. Based on this evaluation, modifications for data acquisition and analysis that aim to reduce bias, increase precision and provide higher efficiency may be made. The overall goal is to integrate new methods into current protocols and provide a clearer understanding of the species trends and population status and to fill as many information gaps as possible.

Monitoring Coho Salmon and Steelhead Trout
in the San Francisco Bay Area

Coho salmon (Oncorhynchus kisutch) and Steelhead trout (Oncorhynchus Mykiss), both members of the Salmonidae family, are U.S. federally endangered species native to the Pacific West. Some factors contributing to overall population decline include commercial fishing, habitat loss and changing climate conditions. This decline has led to the implementation of salmon monitoring techniques used to understand population trends and provide data across multiple life-stages. The National Park Service (NPS) monitors several watersheds in Marin County, California including Olema Creek, Pine Gulch Creek, and Redwood Creek. Institute for Wildlife Studies is working with NPS to evaluate the effectiveness of the San Francisco Bay Area Network (SFAN) salmon monitoring techniques. 

Juvenile Coho