Cooperative Fish and Wildlife Research Units Program: California
Education, Research and Technical Assistance for Managing Our Natural Resources

California Project

Integration of molecular methods into predator diet analysis to advance understanding of juvenile Chinook salmon predation mortality in the Delta

January 2020 - December 2022


Participating Agencies

  • Metropolitan Water District

The objective of this project is to measure the detectability half-life of juvenile Chinook Salmon DNA within the digestive tract of two common predators in the Sacramento-San Joaquin Delta and use this information to compare consumption estimates based on visual and molecular analyses from field collected stomachs. High mortality rates of juvenile Chinook in the Sacramento – San Joaquin Delta have been considered a result of non-native species predation on migrating smolts. Although this is the most common hypothesis, it has been difficult to test because predator stomach contents quickly becomes unidentifiable. In contrast, molecular analyses of gut content can identify species and estimate number of individuals in a mixture for a longer duration. For this project, we have partnered with researchers at the University of California Davis, USGS, and NOAA. The results from this project will provide information necessary to assist managers in understanding the impact of predation on salmon populations in the Delta. This is extremely valuable, since it has been difficult to quantify the effect of these predators on the population level.

Theses and Dissertations Publication Date
Dick, C. Comparing Molecular Methods to Estimate Fish Stomach Contents and Gastric Evacuation Rates: Implications for Measuring the Impacts of Predation on Central Valley Chinook Salmon. M.Sc thesis. California State Polytechnic University, Humboldt July 2022