Viability assessment for Pacific salmon and steelhead listed under the Endangered Species Act : southwest

Abstract

This report from the Southwest Fisheries Science Center covers 10 ESA-listed Evolutionarily Significant Units (ESUs) and Distinct Population Segments (DPSs) that lie wholly or partially in California. In this review, we consider 1) new information relevant to the delineation of ESU/DPS boundaries, and 2) new information on status and trends in abundance, productivity, spatial structure and diversity specifically addressed by viability criteria previously developed by Technical Recovery Teams (TRTs). These viability assessments summarize current information (through the 2014–2015 spawning year where available) with respect to the viability criteria developed by the TRTs. Consequently, the current assessments consider not only changes in populations that have occurred since the 2010 assessments but also the status of populations and ESUs/DPSs in relation to the viability criteria developed by the TRTs. For eight of the ESUs/DPSs (Southern Oregon/Northern California Coho Salmon, Central California Coast Coho Salmon, California Coastal Chinook Salmon, Northern California Steelhead, Central California Coast Steelhead, South-central California Steelhead, Southern California Steelhead, and California Central Valley Steelhead) the new information suggests that there has been no change in extinction risk since 2010 viability assessments. For two ESUs (Central Valley Spring-run Chinook Salmon, and Sacramento River Winter-run Chinook Salmon) the new information suggests a change in extinction risk. The viability of Central Valley Spring-run Chinook salmon appears to have improved since the 2010 assessment, but this ESU is far from being viable and is still facing relatively high extinction risk. The viability of Sacramento River Winter-run Chinook Salmon has been reduced and the ESU faces greater extinction risk since the 2010 assessment.