Thursday August 1, 2024
Northern California Water Association —
Central Valley Chinook salmon experience many stressors at each of their life-cycle stages from eggs in the upper river through adulthood. One of the stressors that we know the least about is the role predation plays in the low survival rates of juvenile fish as they migrate downstream and out to the ocean. These losses in the middle reaches of the region’s rivers negate and squander costly water management and restoration actions that are performed with the goal of enhancing salmonid survival in earlier life-cycle stages. To help advance the science and a better understanding of predation, FISHBIO and a coalition of San Joaquin Valley water agencies have conducted a five-year study to better understand and then address predation by non-native species to help protect California’s declining native fish populations. We encourage you to watch this short film–A Startling Picture–that describes the research and the study, which suggests that predation by non-native fish species is having a significant impact on juvenile Chinook salmon, with population-level losses exceeding 50% under ideal conditions, and many salmon not surviving through the rivers to reach the Delta.
This new study calls for additional research to fully quantify the impact of predation and to integrate predation analysis into our management strategies, which will be very helpful. The impacts of predation in the Sacramento River system have been monitored and analyzed in a study by Dylan Stompe that was published in 2020, titled Sacramento River Predator Diet Analysis: A Comparative Study.