Response of Fathead Minnow Populations to an Exogenous Estrogen

Endocrine disrupting compounds (EDC’s) are found worldwide in aquatic ecosystems and can lead to developmental and reproductive disruption in fishes; however, little is known about the population level consequences of exposure to EDC’s.  Understanding population level responses to EDC exposure is critical to the conservation and management of a wide variety of fishes.  We evaluated the effects of 17alpha-ethinylestradiol (EE2), the synthetic estrogen in human birth control, on fathead minnow (Pimephales promelas) population dynamics in aquatic mesocosms.  We introduced 5 male and 5 female fish to each of 28 1100L mesocosms and exposed fish to 4 treatment concentrations of EE2 (0, 5, 10, and 20ng/L) for 126 days.  Each treatment had 7 replicates arranged in a randomized block design.  Adult survivorship, egg production, numbers and size of offspring and biomarkers of estrogen exposure were collected during the experiment and used to parameterize stage-structured population models. Our experimental and modeling results indicated that fish populations can be negatively impacted by environmentally relevant concentration of EE2.