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 Cy prinodon variegatus were examined in a 180-day flow-through exposure. The s tudy was initiated with embryos less than 24 h postfertilization and monito red through hatch, maturation growth, and reproduction under continuous exp osure to mean measured TBT concentrations of 5.4, 3.2, 1.3, 0.66, and 0.41 mu g TBT/L. Progeny isolated at the onset of reproduction by the parental g eneration (F-0) were monitored for survival as embryos, survival as fry/juv eniles, and growth 30 days postisolation. TBT, at a concentration of 5.4 mu g/L, significantly reduced embryo survival of the F-0 generation sheepshea d minnows. By day 145 of the exposure, significant effects to the survival of this generation increased and included all test concentrations greater t han or equal to 0.66 mu g/L. Survival of 0.66 mu g/L was reduced 59% relati ve to control survival by termination of the F-0 generation. Growth of F-0 generation organisms as measured by standard length was significantly reduc ed only on day 90 at 3.2 mu g/L, however no significant reductions of wet o r dry weight related to treatment concentration were detected. Due to compl ete mortality of organisms exposed to 5.4 Clgn by study day 7, effects to f ecundity and progeny were monitored at measured concentrations of 3.2, 1.3, 0.66, and 0.41 mu g TBT/L. Fecundity, as measured by the production of via ble eggs produced per female per day, was unaffected by any of the test tre atments. AU F-1 generation embryos isolated from treatment chambers into 3. 2 mu g/L died, Survival, standard length, wet and dry weight of the FI gene ration at the remaining treatment concentrations were unaffected. The resul ts of this study indicate that exposure to TBT reduced survival of the F-0 generation sheepshead minnow and establishes the lowest observed effect con centration (LOEC) as 0.66 mu g TBT/L, and the no observed effect concentrat ion (NOEC) as 0.41 mu g TBT/L for this species.