Early life‐stage toxicity test with tidewater silversides ( Menidia Peninsulae ) and chlorine‐produced oxidants

Early life‐stage toxicity tests (continuous exposure from embryonic stage to 3 weeks or more into the exogenous feeding stage) with North American marine fishes have been conducted almost exclusively with cyprinodontids. In this report, we present methods for testing a representative of another family, Atherinidae. Embryos of the tidewater silverside Menidia peninsulae (Goode and Bean) were obtained by a laboratory spawning procedure that required lighting and tidal (current) stimuli. A 28‐d toxicity test with chlorine‐produced oxidants (CPO) began with stage 21 and 22 embryos (approximately 36 h old). Average measured CPO concentrations in exposure water were nondetectable (< 0.01 mg/L) in the control and in the two lowest exposure concentrations, and 0.01, 0.04 and 0.21 mg/L. Survival of embryos to hatching averaged 99%, with no significant difference among treatments. Although no fish survived exposure to 0.21 mg CPO/L, survival was ≥ 88% in the control and the four other CPO treatments. Average wet weights of individual fish ranged from 11.7 mg in 0.04 mg/L to 13.2 mg in 0.01 mg/L, with no significant difference among treatments.