Monitoring juvenile Chinook salmon outmigration using rotary screw traps on the Sacramento River near Delta Entry

The California Department of Fish and Wildlife (CDFW) issued Incidental Take Permit No. 2081-2019-006-00 (ITP) to the California Department of Water Resources (DWR) on March 31, 2020, for the long-term operation of the State Water Project (SWP) in the Sacramento San Joaquin Delta (Delta). Condition 7.5.2 of the ITP requires the development and establishment of a spring-run Chinook salmon (Oncorhynchus tshawytscha) juvenile production estimate (JPE) to increase understanding of the impacts that water operations have on the spring-run Chinook salmon population in the Sacramento River watershed and to inform the development of minimization measures to reduce take of spring-run Chinook salmon at Delta fish salvage facilities. As a part of the JPE effort, CDFW began operating a new rotary screw trap (RST) monitoring station on the lower Sacramento River near River Mile (RM) 75, approximately 5 miles below the confluence of the Feather and Sacramento Rivers, in January 2022. This RST location represents the lowest point in the Sacramento River Watershed where juvenile salmon are trapped prior to entering the Delta and thus is also referred to as the “Delta Entry” site. The expanded juvenile monitoring effort will help resource agencies and water managers identify numbers of salmon emigrating from the Sacramento and Feather River watersheds and contributing to the spring-run Chinook salmon population entering the Delta. Data collected by the RST site at the Lower Sacramento River provides information on the temporal distribution, relative abundance, and race composition of juvenile Chinook salmon; and temporal distribution and relative abundance of steelhead trout (O. mykiss) emigrating from the upper Sacramento River and Feather River to the Delta. Salmonid data collected from the Lower Sacramento River RST, among other datasets, is also used by the Salmon Monitoring Team (SaMT) to understand the movement of juvenile salmon in the Sacramento River Watershed to estimate the number of winter-run and spring-run Chinook salmon that have entered the Delta. SaMT is a real-time operations monitoring team required by Condition of Approval 8.1.2 of the ITP which meets weekly from October through June, to provide advice for real-time management of SWP operations to DWR, CDFW, and the Water Operation Management Team (WOMT) to minimize take of winter-run and spring-run Chinook salmon in the Delta.