Study: smallmouth bass harmed by endocrine disruptors, pathogens, and parasites

December 14, 2015 | 3:29 PM

A smallmouth bass was found in the Susquehanna River with a rare, cancerous tumor found in 2014.

COURTESY PENNSYLVANIA FISH AND BOAT COMMISSION

A smallmouth bass in the Susquehanna River with a rare, cancerous tumor found in 2014.

State environmental regulators say they’re getting closer to solving the curious case of death and disease among smallmouth bass in the Susquehanna River. On Monday researchers with the Department of Environmental Protection released a study, which zeroed in on likely causes: endocrine-disrupting compounds and herbicides, as well as pathogens and parasites.

“This study isn’t to find a single smoking gun,” says DEP Secretary John Quigley. “Instead, the purpose is to eliminate the least likely causes, so we can focus on those that are most likely to be harming the bass.”

Endocrine-disrupting compounds and herbicides can come from many sources including industry, agricultural, municipal sewage treatment plants, as well as residential and commercial landscaping.

Since 2005 the Pennsylvania Fish and Boat Commission has documented outbreaks of disease in young bass that left them with open sores and lesions. Researchers have also found intersex fish – adult males with female eggs in their testes – since the early 2000s. The problems have threatened Pennsylvania’s $3.4 billion recreational fishing industry.

“There are thousands of things out there that could cause these effects,” says Fish and Boat commissioner John Arway. “But we do know about some of them. We need to work on minimizing the exposure to some of the chemicals.”

The DEP will now focus more research on the river’s tributaries, however Quigley says agency is still deciding whether it wants to list the main branch of the Susquehanna as officially “impaired.”

“The work on impairment is ongoing,” Quigley says. “Even if the river was listed impaired today, that wouldn’t change anything soon. A declaration of impairment starts a 13-year clock to implement a total maximum daily load (TMDL) for the river. However, we don’t know what the TMDL would be for.”

The DEP intends to make a determination in February and seek public comment. Arway has previously clashed with the DEP about listing the river as impaired. He says he’s hopeful this latest study puts regulators on the right path.

“Although it may not seem like a monumental conclusion,” he says of the study, “I’m optimistic it does put us on a road to begin fixing the river’s problem.”