Gonadosomatic Index and Testis Morphology of Common Carp (Cyprinus carpio) in Rivers Contaminated with Estrogenic Chemicals

To study the effect of estrogenic chemicals on fish, the gonadosomatic index (GSI = [testis weight/body weight] × 100) and testis histology of mature common carp (Cyprinus carpio) from 2 contaminated sites (Ishizu and Wada rivers, Osaka) and a control site were examined between June 1998 and March 2001. The concentration of nonylphenol, bisphenol A and 17β-estradiol in the Ishizu river was 3-4 times higher than in the Wada river. In the pre-breeding and breeding seasons, there were no significant differences in body weight among carp from the 3 sites, the body weight of Ishizu river carp being significantly lower (p