The U.S. Geological Survey found some surprising marine life in Pennsylvania: male fish that were carrying immature eggs.

The USGS said in a press release that the presence of the intersex fish may be a result of tainted water in the Susquehanna, Delaware and Ohio River basins, causing the Pennsylvania Department of Environmental Protection to begin extensive sampling of chemical contaminants.

“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 wastewater treatment plant effluent and other sewage discharges,” said Vicki Blazer, lead study author and a fish biologist.

The researchers found that smallmouth and white suckers exhibited effects from exposure to high levels of endocrine disruptors — chemicals that can cause cancer and birth defects or interfere with the hormone systems in wildlife — though the effects were more dominant in bass.

“The prevalence and severity of the immature eggs in smallmouth bass corresponded with the percent of agricultural land use in the watershed above the collection sites,” Blazer said.

Study sites in the Susquehanna drainage had the highest prevalence of mutated bass. According to the release, this is likely because the percentage of agricultural land use in that particular basin is higher than the other two regions.