Existing in vivo tests (with the exception of the full lifecycle test) are not adequate for assessing the reproductive effects of endocrine disrupting chemicals (EDCs) on fish, and hence the need for partial life-cycle tests has been recognized internationally. In this paper we describe the development of a short-term (6 week) reproductive performance test for EDCs using pair-breeding fathead minnows (Pimephales promelas). In the test, reproductive performance in paired fish is assessed over two 3 week periods, one with exposure to the test chemical and one without. The test is highly integrative and measures effects of exposure to chemicals on fecundity, gonadosomatic index (GSI), vitellogenin (VTG) induction, and secondary sexual characteristics (fat pad and tubercles in males). In this test, exposure to butyl benzyl phthalate (BBP) at a nominal concentration of 100 µg/L (measured concentration between 69 µg/L and 82 µg/L) had no discernible effects on reproductive performance. In contrast, all reproductive parameters measured were affected by exposure to 4-NP, albeit some (e.g. VTG induction and reduction in the prominence of secondary sexual characteristicslowest effective dose between 0.65 µg/L and 8.1 ( 1 µg/L [measured]) were more sensitive than others (e.g. number of eggs and spawnings, where the lowest effective dose was between 8.1( 1 µg/L and 57.7 ( 3 µg/L [measured]). Concentrations of 4-NP at or above 48 µg/L [measured] inhibited reproduction completely.

The incidence of intersex was examined in freshwater fish in one English and three French rivers. Over 331 fish, mainly roach, were sampled above and below the major sewage treatment works (STW) on each river and the incidence of intersex was recorded by histological examination of fish gonads. No intersex conditions were observed in male fish collected either above or below the major STW on the River Ouse in Sussex. In contrast, roach showing primary oocytes in their testes were found in all three French rivers with the incidence ranging from 9 to 21 % of the males. An intersex chubb and gudgeon were also caught, showing that other species can suffer from this pathology. In addition, roach in the River Seine were heavily parasitised with the tapeworm Ligula intestinalis which may impair the reproductive capabilities of the fish.

Fish reproduction is subjected to worrying trends in many aquatic environments. In this study, we report the absence of histological and biochemical alterations in fish sampled in a low contaminated site (characterised by the absence of detectable oestrogenic activity and mutagenicity in sediment extracts). A total of 474 roach (Rutilus rutilus) were monthly sampled during 18 months, and no intersex fish were recorded after careful histological examination, thus indicating that the incidence of this phenomenon may be very low under natural conditions. Furthermore, mean male plasma vitellogenin concentration was 24 ng ml(-1) and was only slightly elevated during the spawning period (up to 120 ng ml(-1)) indicating that these low values may be characteristic of a low contaminated site. Of the male roach, 45.3% were sampled, a sex-ratio that did not significantly deviated from the expected 1:1 ratio between male and female. Results also showed that natural conditions can greatly affect the reproductive cycle of roach. Gametogenesis showed a biphasic pattern with first gonad maturation between September and December and a final maturation occurring at the end of winter/early spring. Under decreasing temperatures, particularly below 6 degrees C, gametogenesis was stopped or even regressed with secondary oocytes becoming rare under histological observation. Conversely, elevated temperatures during the winter lead to an earlier gonad maturation.

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