Life-cycle toxicity of bis(tributyltin) oxide to the sheepshead minnow (Cyprinodon variegatus).

The effects of tributyltin (TBT) to the life cycle of the estuarine fish Cyprinodon variegatus were examined in a 180-day flow-through exposure. The study was initiated with embryos less than 24 h postfertilization and monitored through hatch, maturation, growth, and reproduction under continuous exposure to mean measured TBT concentrations of 5.4, 3.2, 1.3, 0.66, and 0.41 μg TBT/L. Progeny isolated at the onset of reproduction by the parental generation (F0) were monitored for survival as embryos, survival as fry/juveniles, and growth 30 days postisolation. TBT, at a concentration of 5.4 μg/L, significantly reduced embryo survival of the F0 generation sheepshead minnows. By day 145 of the exposure, significant effects to the survival of this generation increased and included all test concentrations ≥0.66 μg/L. Survival of 0.66 μg/L was reduced 59% relative to control survival by termination of the F0 generation. Growth of F0 generation organisms as measured by standard length was significantly reduced only on day 90 at 3.2 μg/L, however no significant reductions of wet or dry weight related to treatment concentration were detected. Due to complete mortality of organisms exposed to 5.4 μg/L by study day 7, effects to fecundity and progeny were monitored at measured concentrations of 3.2, 1.3, 0.66, and 0.41 μg TBT/L. Fecundity, as measured by the production of viable eggs produced per female per day, was unaffected by any of the test treatments. All F1 generation embryos isolated from treatment chambers into 3.2 μg/L died. Survival, standard length, wet and dry weight of the F1 generation at the remaining treatment concentrations were unaffected. The results of this study indicate that exposure to TBT reduced survival of the F0 generation sheepshead minnow and establishes the lowest observed effect concentration (LOEC) as 0.66 μg TBT/L, and the no observed effect concentration (NOEC) as 0.41 μg TBT/L for this species.