Qualitative Larval Fish Sampling at the California Department of Water Resource’s State Water Project

The California Department of Water Resource’s State Water Project utilizes the John E. Skinner Delta Fish Protective Facility (Skinner Fish Facility) to salvage fishes that would otherwise become entrained during operations to divert water from the Sacramento-San Joaquin River Delta (Delta). Water is diverted from the Delta to meet California’s agricultural, municipal, industrial, and environmental needs. The Skinner Fish Facility, located in Contra Costa County and situated ahead of the Harvey O. Banks Pumping Plant, began salvaging fish in 1968 but historically, only recorded fork length measurements for fish greater than 20 millimeters. Beginning in 2009, the Skinner Fish Facility implemented qualitative larval sampling in response to the 2008 U.S. Fish and Wildlife Service Biological Opinion on the coordinated operations of the Central Valley Project (CVP) and State Water Project (SWP). This entailed collecting, retaining, and identifying larval fishes to better understand SWP impacts on Delta Smelt. Qualitative larval sampling took place annually from 2009 through 2025, during the Old and Middle River management period and based upon Delta Smelt spawning (typically mid-February to June). The California Department of Water Resources collected and processed samples from 2020 through 2025. Data from 2009 through 2019 were processed and retained by others and are not included in this dataset.