FATHEAD MINNOW AND BLUEGILL SUNFISH LIFE-STAGE RESPONSES TO 17?-1 ESTRADIOL EXPOSURE IN OUTDOOR MESOCOSMS

Developmental and reproductive effects of 17?-estradiol (E2) exposure on two generations of 7 fathead minnows and one generation of bluegill sunfish were assessed. Fish were exposed to E2 8 for 6 continuous weeks in outdoor mesocosms simulating natural lake environments. First 9 generation fish were exposed while sexually mature. Second generation fathead minnows were 10 exposed either during early development, sexual maturity, or both stages. Multiple endpoints 11 were measured to assess effects of E2 exposure on fecundity and fish health and development. 12 Plasma vitellogenin concentrations were highly variable in all fish. Differences in egg 13 production timing for both species indicate differences in fecundity between females exposed to 14 E2 and controls. First generation fathead minnows exposed to E2 had lower body condition 15 factors and reduced secondary sexual characteristic expression by males. Only a difference in relative liver weight was observed in second-generation fathead minnows. First generation 17 bluegill males exposed to E2 had significantly smaller testes compared to controls. Although 18 fish response was highly variable, results indicate that exposure to E2 at environmentally 19 relevant concentrations affect fathead minnow and bluegill sunfish health and development, which may have implications for the health and sustainability of 21 fish populations. Furthermore, 22 exposure timing and environmental factors affect fish response to E2 exposure.