Surveys of U.K. rivers have shown a high incidence of sexual disruption in populations of wild roach (Rutilus rutilus) living downstream from wastewater treatment works (WwTW), and the degree of intersex (gonads containing both male and female structural characteristics) has been correlated with the concentration of effluent in those rivers. In this study, we investigated feminized responses to two estrogenic WwTWs in roach exposed for periods during life stages of germ cell division (early life and the postspawning period). Roach were exposed as embryos from fertilization up to 300 days posthatch (dph; to include the period of gonadal sex differentiation) or as postspawning adult males, and including fish that had received previous estrogen exposure, for either 60 or 120 days when the annual event of germ cell proliferation occurs. Both effluents induced vitellogenin synthesis in both life stages studied, and the magnitude of the vitellogenic responses paralleled the effluent content of steroid estrogens. Feminization of the reproductive ducts occurred in male fish in a concentration-dependent manner when the exposure occurred during early life, but we found no effects on the reproductive ducts in adult males. Depuration studies (maintenance of fish in clean water after exposure to WwTW effluent) confirmed that the feminization of the reproductive duct was permanent. We found no evidence of ovotestis development in fish that had no previous estrogen exposure for any of the treatments. In wild adult roach that had previously received exposure to estrogen and were intersex, the degree of intersex increased during the study period, but this was not related to the immediate effluent exposure, suggesting a previously determined programming of ovotestis formation.

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The high incidence of intersex roach (Rutilus rutilus) in some United Kingdom rivers that has been associated with exposure to sewage treatment works (STWs) effluent led us to hypothesize that top predator fish also may be affected by estrogenic chemicals, because they are likely to bioaccumulate lipophilic compounds through a predator-prey relationship. To investigate this possibility, pike (Esox lucius) were sampled both upstream and downstream of STWs and then examined for total estrogenic activity of their bile, as measured using a yeast-based estrogen assay to determine the degree of recent exposure of the pike to estrogens and vitellogenin induction, and for possible disruption of sexual development, as measured using histological analysis of the gonads. No evidence of severe disruption was found in the sampled fish, which came from 16 sampling sites that were representative of English rivers. However, 14% of pike were intersex, of which 15 of 16 showed patches of male germ cells among predominantly female gonadal tissue. The incidence of masculinization was independent of whether the pike had been sampled upstream or downstream of STWs. Although pike are gonochoristic, it is not known if this masculinization of presumptive female pike is normal or, instead, indicative of endocrine disruption. Vitellogenin concentrations were not elevated in male pike at sites either upstream or downstream of STWs. The results suggest that sexual disruption is not common in pike, a fish at the top of the food chain in the freshwaters of England.