FotorCreated.jpg

The intrusion of chemicals, pathogens and parasites into local tributaries have been identified as possible causes for a rapid decline of the smallmouth bass population in the Susquehanna River.

(File)

The intrusion of chemicals, pathogens and parasites into local tributaries have been identified as possible causes for a rapid decline of the smallmouth bass population in the Susquehanna River.

The Pennsylvania Department of Environmental Protection released findings of a multi-year study Monday on the causes behind the decade-long smallmouth bass population crash. Smallmouth bass have been found dead while others have been observed with white lesions, sores and eroded fins.

The study determined that the presence of endocrine disruption compounds, herbicides, pathogens and parasites in the river are the most likely causes. Now state and federal agencies are working to determine how these substances are entering the river, said DEP Secretary John Quigley.

"DEP will continue to monitor the health of the Susquehanna River," Quigley said. "We will move research into the tributaries to try to find the sources of potential water quality issues."

The concentration of endocrine disruption compounds and herbicides were higher at the some sites along the river, according to the study. Male smallmouth bass have been found to have changed sex -- a sign that they've been exposed to endocrine disruption compounds.

In 2014, a smallmouth bass with a large malignant tumor was caught in the Susquehanna River by an angler near Duncannon. Intersex fish and other anomalies have also been found.

EDCs are chemicals that interfere with animals' endocrine, or hormone, systems. Quigley said EDCs can come from many sources, including industry, agriculture, municipal sewage treatment plants, residential/commercial landscaping, golf courses and roadways.

DEP Water Program Specialist Dustin Shull said they are constantly collecting and analyzing new data that will help identify the causes for the smallmouth bass population problem.

Quigley said the purpose of the study was not "to find a single smoking gun" but rather to eliminate the least likely causes.

Shull said the DEP now will be able to focus its resources on more likely causes.

The cause that are the least likely to have contributed to the decline include, but are not limited to, food quality, temperature, pH levels, dissolved oxygen, ammonia, or toxic chemicals, according to the study.

The study found there were also a number of uncertain causes that may have lead to the population decline. Those uncertain causes include algal and bacterial toxins, interspecific competition, food quality, egg quality and habitat.

Shull said they will need to continue studying the river and smallmouth bass population to clarify and narrow the causes of the population decline.