Nebraska Academy of Sciences
Transactions of the Nebraska Academy of Sciences and Affiliated Societies
Date of this Version
12-30-2025
Document Type
Article
Abstract
Rotenone is commonly used to remove undesirable fish species and support recreational fisheries. Lake Ogallala, a 263-ha tailwater reservoir located in western Nebraska, has had a history with rotenone use dating back to 1969. While past renovations of the reservoir have documented impacts on water quality, aquatic vegetation establishment, and benthic invertebrate and fish communities, zooplankton responses had not been studied. To evaluate potential effects, we compared zooplankton densities and community composition before and after the most recent renovation. Monthly samples were collected from April – September in 2023 (pre-renovation) and 2024 (post-renovation) using an 80-μm circular plankton net at nine standardized sites. Zooplankton were identified to predetermined taxonomic groups and enumerated to calculate mean total and taxon-specific densities. Community composition was evaluated using percent composition and non-metric multidimensional scaling (NMDS) with a one-way analysis of similarity (ANOSIM). Twelve taxa were recorded pre-renovation and 11 post-renovation; two taxa were exclusive to the pre-renovation period and one to the post-renovation period. Overall, total densities and monthly community compositions remained similar between years (R =0.01, p = 0.32). The rapid recovery observed in this study is likely due to the recolonization of zooplankton from Lake McConaughy into Lake Ogallala as well as the timing of the rotenone application (fall) when zooplankton eggs were not vulnerable to mortality. This study provides insight into how zooplankton communities in Lake Ogallala respond to chemical renovation and may help inform management decisions on restocking fish following piscicide applications in similar systems.
doi:10.32873/unl.dc.tnas.45.9
Comments
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