Effects of Kelthane and Pydrin on Early Life Stages of Fathead Minnows (Pimephales promelas) and Amphipods (Hyalella azteca)

Abstract

Embryonic, Larval, and early juvenile stages of fathead minnows (Pimephales promelas) and juvenile amphipods (Hyalella azteca) were exposed to Kelthane, and fathead minnows were exposed to Pydrin in a small self-contained continuous-flow diluter system for approximately 30 days. Survival of the newly hatched larvae was found to be the most sensitive measure of the effect on fathead minnows of both pesticides. Pydrin was approximately 90 times more toxic to fathead minnows than Kelthane. The lowest effect concentrations of Kelthane and Pydrin were 13 times lower than the 96-h median lethal concentration (LC50) values for fathead minnows exposed in Lake Superior water. The upper and lower chronic limits for Kelthane were 39 and 19 µg/litre for fathead minnows and 33 and 19 µg/litre for amphipods. The chronic limits for Pydrin and fathead minnows were 0.43 and 0.33 µg/litre. The mean bioconcentration factors (BCFs) for Kelthane were 3 700 with fathead minnows and 10 000 with amphipods. The mean BCF for Pydrin with fathead minnows was 3 200. Residue concentrations and BCFs for both pesticides increased with increased water concentrations.