Abstract
To investigate whether male fish are really feminized by estrogen-like substances exist in effluent of sewage treatment plants, eight-week exposure tests were performed using carp in water tanks received effluent from a sewage treatment plant. Serum vitellogenin (VTG) was selected as a biomarker of feminization. When the first run of the tests launched in the early spring of 2000, male and female carp were exposed in the same tank receiving treated sewage, VTG concentrations of male carp exposed to the effluent increased with time, while it reduced after the cease of exposure to the effluents. In the control experiment using dechlorinated tap water, increase in VTG was not recognized in male carp. Two more runs of the test were performed in the summer of 2000 and early spring 2001. However, significant increase in VTG could not be observed in male carp. The estrogenic activities in the effluents were almost in the same level throughout all the tests; therefore, the seasonal timing of exposure might be important for understanding this inconsistent phenomenon.
