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A smallmouth bass, caught by an angler last Nov. 3 in the Susquehanna River near Duncannon, has been confirmed as having a malignant tumor.

(Contributed photo)

A Susquehanna River smallmouth bass has been confirmed as having a cancerous tumor on its mouth, according to the Pennsylvania Fish and Boat Commission.

Here's the backstory on what's been going on with the Susquehanna River and its smallmouth bass fishery since 2009.

The fish, caught by an angler last Nov. 3 near Duncannon, is believed to be the first smallmouth bass in Pennsylvania to be documented with such a tumor. Cancerous growths and tumors on fish are extremely rare in Pennsylvania and throughout the U.S., but they do occur.

The cancerous tumor was confirmed by both the U.S. Fish and Wildlife Service and the Aquatic Animal Health Laboratory at Michigan State University.

Although it's only one individual fish, commission Executive Director John Arway described it as further evidence that the health of the fish community in the river is being compromised.

"As we continue to study the river, we find young-of-year and now adult bass with sores, lesions and more recently a cancerous tumor, all of which continue to negatively impact population levels and recreational fishing," he said. "The weight-of-evidence continues to build a case that we need to take some action on behalf of the fish."

Commission biologists have observed more than 22,000 adult smallmouth bass in surveys in the Susquehanna River basin since 2005 and have not documented any other fish with obvious signs of tumors. However, they continue to find high rates of sores and lesions on young-of-year bass during late spring and early summer surveys.

'We just stared at it in shock and awe' says John Arway, executive director of the Pennsylvania Fish and Boat Commission, of cancerous fish

Karen Murphy, acting secretary of the Pennsylvania Department of Health, said "There is no evidence that carcinomas in fish present any health hazard to humans. However, people should avoid consuming fish that have visible signs of sores and lesions."

Arway said anglers must make their own decisions on whether or not to consume fish.

However, catch-and-release regulations are already in place for smallmouth bass on 98 miles of the middle portion of the Susquehanna River, where the cancerous fish was captured, and on the lower 31.7 miles of the Juniata River from Port Royal to the mouth.

The commission first documented disease-related mortality in young-of-year bass in the Susquehanna River in 2005, and an ongoing decline in abundance of bass in the river.

Since 2012, the commission has twice unsuccessfully petitioned the Pennsylvania Department of Environmental Protection to add the river to the state's bi-annual list of impaired waterways. Such a designation would launch a timetable for developing a restoration plan for the river.

"If we do not act to address the water quality issues in the Susquehanna River, Pennsylvania risks losing what is left of what was once considered a world-class smallmouth bass fishery," Arway said. "DEP is expected to release its 2016 list of impaired waters in late fall. We are urging them once again to follow the science and add the Susquehanna River to the list."

Commission staff are continuing to work with DEP, the U.S. Geological Survey, the U.S. Fish and Wildlife Service, the U.S. Environmental Protection Agency and other partners to better understand what factors are impacting the bass inhabiting the middle Susquehanna and lower Juniata rivers.