A smallmouth bass with a cancerous tumor. (Courtesy Pennsylvania Fish and Boat Commission)

A smallmouth bass caught in the Susquehanna River has a cancerous tumor, the Pennsylvania Fish and Boat Commission confirmed this week. Cancer is rare in fish, and the finding adds to an existing concern among wildlife officials about the health of fish living in the region.

“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,” the commission's executive director, John Arway, said in a statement. “The weight of evidence continues to build a case that we need to take some action on behalf of the fish.”

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The fish was caught last year; it is the first case of cancer in a smallmouth bass confirmed in the river, the commission said.

Officials started noticing lesions on local bass in 2005, Arway said, and have been petitioning the Pennsylvania Department of Environmental Protection ever since to get the Susquehanna River included on the EPA's list of "impaired waterways." That campaign so far has been unsuccessful.

The two state agencies strongly disagree over whether the designation is warranted. In response to Arway's concerns, the state DEP said at the time that it made recommendations based on water quality and not species health.

The state DEP did not include the region as an affected site in its most recent biannual report in 2013.

In response, the EPA said it did not have enough information to determine whether the waterway belonged on the list, and left it off. "Although we share the continuing concerns about the health of the smallmouth bass population," the agency said in a statement to NPR, "we do not have sufficient data at this time to scientifically support listing the main stem of the Susquehanna as impaired."

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The Washington Post also took a look at the health of smallmouth bass in in the river in 2013, noting that some wildlife experts consider the species to be a "canary in the coalmine" for potential water pollution.

Arway hopes that the discovery of the cancerous fish will help his agency make its case for the designation. The Fish and Boat Commission already had catch-and-release rules in place for the area where the fish was caught, according to the agency. However, anglers can make their own decisions on whether to actually eat any fish they catch in the area.

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

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