USGS Study May Have Linked Intersexed Fish With Die-Offs In Shenandoah River

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ish in the Shenandoah River appear to be taking birth control, federal biologists say. But they’re still reproducing for now.

Large numbers of abnormally developed smallmouth bass possessing male and female characteristics have been found throughout the Shenandoah River, mostly near agricultural and urban areas, according to federal biologists. Scientists say the fish may have ingested chemicals containing estrogen, including birth control and other medications, and human and animal excrement, said U.S. Geological Survey biologist Vicki Blazer.

Contaminants may enter the rivers through water released from wastewater-treatment plants, and rain that washes poultry litter and manure off farmland, Blazer said.

Although the abnormality hasn’t affected reproduction, Blazer said development of intersex characteristics could be linked to mysterious fish kills that have plagued the river for four years. “I do think the fish kills and intersex are related,” she said. “Many of these chemicals linked to intersex or other reproductive effects also affect immune response and disease resistance.”

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