Cooperative Fish and Wildlife Research Units Program: Colorado
Education, Research and Technical Assistance for Managing Our Natural Resources

The presence of endocrine-disrupting compounds (EDCs) in aquatic ecosystems is widespread and these compounds have been shown to cause developmental and reproductive disruption in wild freshwater fishes worldwide. Although the effects of endocrine disrupting compounds (EDCs) on the individual physiology of animals are well known, less is known about the ultimate population-level consequences, and it is important to begin to understand how exposure to EDCs influences animal population dynamics. We are particularly interested in effects of EDCs on resident Great Plains fish populations and communities that are downstream of large urban centers along the front range of the Colorado Rocky Mountains, such as Boulder, Denver, Fort Collins, and Colorado. We have completed one study investigating the effects of a known endocrine disruptor, 17-β estradiol (E2), on reproductive behavior and success of red shiner (Cyprinella lutrensis), a fish native to the plains region of Colorado. Male exposure to estradiol resulted in elevated plasma vitellogenin concentrations, changes in spermatogenesis, reduced mating coloration and tubercles, altered mating behaviors, and reduced reproductive success with no viable progeny produced. Our results indicate that wild populations of red shiners may face developmental and reproductive difficulties if they are chronically exposed to estradiol. Additional field, laboratory, and mesocosm experiments are currently in progress. Field experiments consist of caging fathead minnows above and below waste water effluents to estimate the effects of exposure on several physiological endpoints. These physiological metrics will be compared to results from more controlled exposures in the lab. Field collections of fish and water chemistry will be made to estimate correlations between water quality and population and community composition. Mesocosm experiments are currently underway to estimate the effects of exposure to 17α-ethynylestradiol (EE2) on survival, reproduction, and recruitment of fathead minnows.