SURVIVAL OF BLUEGILL AND THEIR BEHAVIORAL-RESPONSES DURING CONTINUOUS AND PULSED EXPOSURES TO ESFENVALERATE, A PYRETHROID INSECTICIDE

Juvenile bluegill (Lepomis macrochirus) were exposed to the pyrethroid insecticide esfenvalerate [(S)-alpha-cyano-3-phenoxybenzyl-(S)-2-(4-chlorophenyl)-3-methyl butyrate], continuously for 90 d and for six 11-h pulses. No bluegill survived continuous exposure to esfenvalerate at 0.200 mug/L for 30 d or 0. 100 mug/L for 60 d. The lowest-observable-effect concentration (LOEC) for survival in a 90-d continuous exposure of esfenvalerate was 0.025 mug/L. In comparison, no mortality occurred among fish exposed to pulsed doses of up to 0.200 mug/L. Behavioral responses, including gross body tremors, were highly sensitive indicators of toxicity among pulse-exposed fish, with symptoms appearing within 4 h of exposure to concentrations as low as 0.025 mug/L. Similar behavioral responses were observed after continuous exposure to 0.025 mug/L esfenvalerate. Behavioral responses were observed at concentrations an order of magnitude less than concentrations impacting growth or survival in simulated field studies. These results provide encouraging evidence that laboratory studies designed to simulate field exposure conditions can be predictive of concentrations causing mortality and other adverse effects.