In the central valley of california, there are four distinct runs of chinook salmon (the fall, late fall, winter, and spring runs)

The juveniles of these runs mix to various degrees during their seaward migrations through the sacramento SAN joaquin delta (the delta ). Estimating the juvenile abundance of these runs as they enter the delta at sacramento and exit the delta at chipps island is viewed by the scientific and management communities as a critical element in improving information for restoration and water management in the delta. This is especially true for winter run, which is listed as endangered under the endangered species act.a multi year, multi agency project was initiated in 2016 with the goal of developing datasets and statistical methods that would allow for the reliable estimation of juvenile winter run abundances at two key monitoring locations sacramento river trawl (delta entrance) and the chipps island trawl (delta exit). During years 2016 2021, project data were collected from several sources (1) paired releases of acoustic tagged and coded wire tagged hatchery juveniles (2) trawl catch and effort data and (3) tissue samples of trawl caught juveniles used to determine genetic run type. Collectively, these data provide the information needed to determine trawl efficiency (i.e., the proportion of migrating juveniles captured by trawls), which is then used to estimate juvenile abundance. The objective of this final phase of the project is to finalize the statistical models and results using all years of data. The specific project activities will include, in collaboration with coinvestigators, the following (1) completion of trawl efficiency modeling and winter run abundance estimation for sacramento trawl (2) completion of analyses of fish movement at the sacramento and chipps island trawl locations based on acoustic tagged juveniles (3) completion of analyses to determine potential improvements in future data collection efforts and (4) completion of reports and peer review manuscripts detailing the results and conclusions of the overall project.