We have developed methods for obtaining embryos and conducting early life-stage toxicity tests (continuous exposure from the embryonic stage to approximately three weeks or more into the exogenous feeding stage) with three estuarine species of atherinid fishes. Early life-stage tests were conducted for 28 days with Menidia beryllina, M. menidia, and M. peninsulae and the insecticide chlorpyrifos. Responses of the three species were similar: upper chronic values (“effect” concentrations) ranged from 0.48 to 1.8 µg chlorpyrifos/L and lower chronic values (“no effect” concentrations) ranged from 0.28 to 0.75 µg/L. Chlorpyrifos exposure did not affect survival of embryos to hatching which averaged 91 to 93% for each species. In treatments in which no adverse effects were observed, combined survival of M. menidia embryos and hatched fish averaged 51% and fish weights averaged 23 mg; for M. peninsulae, 69% and 13.6 mg; and for M. beryllina, 81% and 8.7 mg. Chlorpyrifos bioconcentration factors (concentration in whole fish ÷ average measured concentration in water) averaged 220 for M. beryllina, 460 for M. peninsulae, and probably < 420 for M. menidia.

From these three species, toxicologists may select an Atlantic or Gulf Coast species that occurs in either high or low salinity.