Intersex Fish Found in Susquehanna River, Delmarva Lakes

“Intersex” fish – male fish with female traits – are showing up in more Chesapeake Bay region waterways. Government and university scientists have recently collected intersex smallmouth and largemouth bass from several waterways in Pennsylvania, Delaware and Maryland.

More than 90 percent of adult male smallmouth bass collected during studies on the Susquehanna River this year contained immature egg cells, according to a biologist with the U.S. Geological Survey.

The Susquehanna is the second major Chesapeake Bay river where scientists have found intersex fish. The Potomac River, as well as the Shenandoah and Monocacy rivers, have documented cases of intersex fish.

Intersex fish have recently been discovered in lakes and ponds on the Delmarva Peninsula as well. Researchers with the University of Maryland sampled six lakes and ponds in Maryland and Delaware and found intersex fish in all of the tested water bodies.

Scientists believe that male fish may develop these female trails through exposure to hormone-mimicking chemicals in the water. More research is needed, but these chemicals may come from agricultural pesticides, poultry waste, human personal care products or pharmaceuticals.

For more details about intersex fish in the Susquehanna River, read this Nov. 2 Baltimore Sun article. For more information about intersex fish found on Delmarva, read this Nov. 11 Baltimore Sun article.