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

Juvenile bluegill (Lepomis macrochirus) were exposed to the pyrethroid insecticide esfenvalerate no-3-phenoxybenzyl-(S)-2-(4-chlorophenyl)-3 -methyl butyrate], continuously for 90 d and for six 11-h pulses. No b luegill survived continuous exposure to esfenvalerate at 0.200 mug/L f or 30 d or 0. 100 mug/L for 60 d. The lowest-observable-effect concent ration (LOEC) for survival in a 90-d continuous exposure of esfenvaler ate was 0.025 mug/L. In comparison, no mortality occurred among fish e xposed to pulsed doses of up to 0.200 mug/L. Behavioral responses, inc luding gross body tremors, were highly sensitive indicators of toxicit y among pulse-exposed fish, with symptoms appearing within 4 h of expo sure to concentrations as low as 0.025 mug/L. Similar behavioral respo nses were observed after continuous exposure to 0.025 mug/L esfenvaler ate. Behavioral responses were observed at concentrations an order of magnitude less than concentrations impacting growth or survival in sim ulated 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 ef fects.