Balancing Fisheries Management and Water Uses for Impounded River Systems

Changes in Reservoir Larval Fish Assemblages Following the Extirpation of Gizzard Shad

Mark T. Porath and Jeffrey J. Jackson

doi: https://doi.org/10.47886/9781934874066.ch40

Abstract.—Larval fish assemblages are an important component of reservoir communities by providing an abundant prey source critical to the recruitment of predator species into recreational fisheries. We examined the composition, abundance, and length distribution of larval fish in several Nebraska flood-control reservoirs from 2000 to 2004 that were stocked with walleye Sander vitreus and experienced weather-related extirpations of gizzard shad Dorosoma cepedianum. Gizzard shad dominated the larval fish assemblages with a wide-ranging length distribution prior to extirpation. After extirpation, Centrarchidae species eventually filled the void with a smaller and truncated length-frequency distribution. Larval fish densities varied widely throughout the study period with fewer prey available to predators with gizzard shad present in the assemblages. The extirpation of gizzard shad elicited a significant change to the larval fish assemblages of these reservoirs but did not prohibit the survival of stocked walleye fingerlings.