Research Product

Flow-through acute and early life-stage (ELS) toxicity tests were conducted with topsmelt (Atherinops affinis), a Pacific Coast saltwater fish, and fenvalerate, a synthetic pyrethroid insecticide. The 96-h LC50 for juvenile fish was 0.66 µg/L. In the 30-d ELS test with laboratory-spawned embryos, average measured fenvalerate concentrations were nondetectable (< 0.075 µg/L) in two control treatments, 0.14, 0.34, 0.82, 1.5, and 3.2 µg/L. Survival of embryos to hatching ranged from 94% to 100%, with no statistically significant difference among treatments. No fry survived exposure to fenvalerate concentrations > 0.82 µg/L; overall survival in lower concentrations and control treatments ranged from 86% to 97%. There were no consistent concentration-dependent differences in weight between fish in the carrier-control treatment and fish exposed to fenvalerate. Mean wet weights of surviving fish ranged from 16.9 mg in 0.34 µg/L to 20.3 mg in 0.14 µg/L. The average bioconcentration factor for fish exposed to 0.14 and 0.34 µg fenvalerate/L was 315.