One fish, two fish, boy fish? girl fish?

In a recent study by the U.S. Geologic Survey, researchers found intersex fish in the Delaware, Susquehanna, and Ohio River basins of Pennsylvania.  Small mouth bass, whitesuckers, and redhorse suckers were collected from sixteen sites including the Swatara Creek, Juniata River, Conodoguinet Creek, Yellow Breeches Creek, and the Susquehanna River in central Pennsylvania.

Male small mouth bass from all sites were carrying immature eggs, with the lowest prevalence in the Ohio basin, intermediate in the Delaware, and highest in the Susquehanna basin.  And while the white suckers and redhorse suckers did not have intersex characteristics, some of the white suckers had a precursor to egg development in their blood.

The culprit: endocrine disrupting chemicals that alter hormone release.  These chemicals most likely find their way into our waters from agriculture sources like manure, pesticides, and herbicides, and from human sources like wastewater treatment plant effluent and sewage discharges. Intersex fish were more prevalent in areas where there were more agricultural operations and the severity of intersex conditions increased at sites downstream from wastewater discharges.

The researchers were surprised by the number of fish affected and the severity. These changes can have negative long-term effects that can threaten fish populations, as eggs inside the male fish will not mature and chemicals in the water can impact their immune systems, making them more susceptible to diseases.

The Pennsylvania Department of Environmental Protection (DEP) is conducting a multiyear analysis of the rivers and collecting and analyzing water and sediment samples to find out exactly which chemicals are out there and in what concentrations.

Jen Quinn is PennFuture's central Pennsylvania outreach coordinator and is based in Harrisburg.