Data characterize zooplankton in Shelbyville Reservoir, Illinois, United States of America. Zooplankton were sampled with a conical zooplankton net (0.5m diameter mouth) when water was deeper than 2 m and by grab sample when water was shallower. Zooplankton samples were concentrated and subsampled with a Hensen-Stempel pipette following protocols described in Detmer et al. (2019). Zooplankton were identified to the lowest feasible taxonomic unit according to Pennak (1989) and Thorp and Covich (2001) and were enumerated in a 1 mL Sedgewick-Rafter cell. Subsamples were analyzed until at least 200 individuals were enumerated from each site.were counted across for each of the three main taxonomic groups (cladocerans, copepods, and rotifers). Given the variation in zooplankton concentrations at each site, this process often lead to far more than 200 individuals being counted (x̄ = 269, min = 200, max = 487). A summary of the sample size from each site can be found in Supplementary Table S2. Abundances were corrected for volume of water filtered. For rare taxa (< 20 individuals per sample), all individuals were measured for length. For abundant taxa, length measurements were collected on the first 20 organisms of each abundant taxon encountered in a subsample. Dry mass was calculated from equations for microcrustaceans, rotifers, and Chaoborus sp. (Rosen ,1981; Botrell et al., 1976; Dumont and Balvay, 1979).