SCHOENFUSS, H.L.*; MARTINOVIC, D.; SORENSEN, P.W.: Effects of Water-Borne 17b-Estradiol on Reproductive Fitness in Two Species of Fish

To assess the effects of endocrine disrupters on the reproductive health of male fish, we exposed male goldfish (a substrate spawner) and fathead minnows (a nest guarding species) to waterborne estradiol at a concentration found in some European and North American sewage treatment plant (STP) effluents (50 ng/l). After being exposed for 10 weeks, male goldfish had detectable levels of vitellogenin, reduced sperm production, and were less likely to spawn with females when given the opportunity. Similar but even smaller changes were seen in male goldfish exposed to STP effluent. These results suggest that exposure to endocrine disrupters at relevant concentrations has adverse effects on the reproductive health of male fish. To test this hypothesis and to examine whether changes in reproductive health are exasperated in competitive spawning situations with non-exposed fish, we exposed male fathead minnows for 21 days and allowed them to spawn with mature females. Preliminary results indicate that they will spawn successfully but experience reduced reproductive success when placed with non-exposed males. These studies demonstrate that EDC exposure at relevant concentrations has subtle effects on male fertility and may have broader implication for fish populations. Results and ramifications of ongoing studies will be discussed. Support provided by the Metropolitan Council Environmental Services, St. Paul, the Minnesota Water Resource Center, and the National Sea Grant.