Altered social behavior and sexual characteristics in mosquitofish (Gambusia holbrooki) living downstream of a paper mill

Several environmental contaminants have been found in paper mill effluent including substances with androgenic properties. The presence of androgenic substances in paper mill effluent was also indicated in the present study which demonstrated masculinized anal fins of female mosquitofish from the paper mill effluent contaminated Fenholloway River. In addition, when compared to the nearby Econfina River, which does not receive paper mill effluent, fewer females from the contaminated river were pregnant, they were smaller and their estradiol concentration exhibited greater variation. Males from the Fenholloway River and the Econfina River had similar sperm counts, but the testes were larger and greater variation in testosterone concentration was observed in male fish from the Fenholloway River. In males and females from the Fenholloway River, liver weights were increased and computer-aided behavior analysis demonstrated a reduction in their social behavior when compared to reference fish. We conclude that a number of sexual characteristics were affected in mosquitofish living in the paper mill contaminated Fenholloway River, with possible adverse effects on the reproduction of this population.