How has exposure to chemical contaminants in the Chesapeake Bay region led to intersex characteristics in fish?

Fish biologist Vicki Blazer with the U.S. Geological Survey (USGS) brings her team to the Shenandoah River in Front Royal, Va., to collect and study smallmouth bass, a species in which intersex characteristics have been linked to chemical contaminants in the Chesapeake Bay region.

Intersex conditions occur when exposure to chemicals disrupts the hormonal systems of an animal, leading to the presence of both male and female characteristics in an animal that should exhibit the characteristics of just one sex in its lifetime. In the case of smallmouth bass, male intersex fish are found with immature eggs in their testes, which indicates exposure to estrogenic and anti-androgenic chemicals.

“The sources of estrogenic chemicals are most likely complex mixtures from both agricultural sources, such as animal wastes, pesticides and herbicides, and human sources from waste water treatment plant effluent and other sewage discharges,” says Blazer, who first discovered intersex characteristics in fish while studying fish kills in the South Branch of the Potomac River and the Shenandoah River.

  • Produced by Will Parson
  • Music/Audio: “A Moment of Jazz” by Ancelin

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