ABSTRACT:
Since 2003, scientists at the U.S. Geological Surveyﾒs National Fish Health Research Laboratory (NFHRL) in Kearneysville, WV have been evaluating the reproductive health of smallmouth bass in the upper Potomac River and its tributaries, including the Shenandoah River. They noted the presence of immature female germ cells (oocytes) in the testes of some of the male fish. This condition, a type of intersex, is evidence of a disturbance in the hormonal system of the fish (i.e., endocrine disruption). Further evidence of endocrine disruption occurs when we detect the presence of vitellogenin in the blood of male fish. Vitellogenin is a protein produced by female fish to form egg yolk and is normally absent in males. In addition to the effects on male fish, a substantial decrease of vitellogenin in females also suggests endocrine disruption.