EFFECTS OF ESFENVALERATE ON THE REPRODUCTIVE SUCCESS OF THE BLUEGILL SUNFISH, LEPOMIS-MACROCHIRUS IN LITTORAL ENCLOSURES

Adult bluegills were exposed to the synthetic pyre throid esfenvalerat e, during a reproduction study conducted in six littoral enclosures lo cated in a 2-ha pond near Duluth, Minnesota. Bluegill reproductive suc cess was determined after two applications of esfenvalerate at nominal concentrations of 0.0, 0.01, 0.08, 0.20, 1.0, and 5.0 mu g/L. Respons es measured were adult behavior and spawning, embryo hatchability, lar val survival until swim-up, young-of-the-year (Y-O-Y) growth, and tota l biomass. All adult bluegills died within one day following the first application at 5.0 mu g/L. Successful spawning and resulting hatching of offspring were observed at all esfenvalerate concentrations except 5.0 mu g/L. Following exposure at 1.0 mu g/L, spawning was delayed fo r 15 days and few or no larvae survived. Bluegill Y-O-Y growth was red uced by 62, 57, and 86% in the 0.08, 0.20, and 1.0 mu g/L esfenvalerat e treated enclosures. Delayed adult spawning and reduced Y-O-Y growth may result in poor Y-O-Y overwinter survival which would result in a d iminished or extirpated year class.