| Abstrakt: |
Sensitivity, expressed as the 96-hr LC50 derived from acute lethality tests, was compared for four ages (day-of-hatch, 7-day, 14-day, and 28-day) of three atherinid fishes:Leuresthes tenais (California grunion),Menidia menidia (Atlantic silverside), andMenidia peninsulae (tidewater silverside). Responses of each age-species combination exposed to the organophosphate insecticide chlorpyrifos and the carbamate herbicide thiobencarb were compared in both static and flowing seawater toxicity tests. Chlorpyrifos was highly toxic to all atherinids (96-hr LC50's ranged from 0.4 to 6.7 µg/ L); toxicity of thiobencarb was approximately two orders of magnitude lower (LC50 values from 199 to 1,405 µg/L). Responses to each pesticide were similar among the three species. Sensitivity was generally highest for 7-day and 14-day age groups, and flowing water tests were more sensitive measures of toxicity than static tests, especially for chlorpyrifos. Comparisons of three computational methods indicate that probit and moving average methods calculate comparable LC50 estimates with the binomial method being the least uniform point estimator. |
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