This data set includes count, location, and ancillary habitat data for fishes sampled in adjacent reaches of Georgiana Slough, Sacramento River, and Steamboat Slough in the northern Sacramento-San Joaquin Delta. It also includes data on the stomach contents of selected individual black basses (Micropterus). Fishes were sampled by boat electrofishing from approximately January-May, 2020-2022, plus gillnetting in 2020. Samples were collected under a stratified random sampling design. Gillnetting involved short duration (~60 minute) sets of monofilament experimental gill nets. Boat electrofishing involved either single or repeated passes along an individual 300 m shoreline transect. Stomach contents data are from fishes that were frozen whole immediately upon collection and later processed in a laboratory.