Fish and Boat Commission Says it's Too Soon to Diagnose Black Spots on Fish

  • Susan Phillips

Courtesy of William Yingling

Fish with black splotches are showing up in Pennsylvania's waterways.


The Pennsylvania Fish and Boat Commission says it will take a lot more work, and a lot more data, to figure out what is causing black spots on small mouth bass in the Susquehanna River. A commission scientist wrote to a fisherman in response to the angler’s pleas for lab tests. The fisherman, William Yingling, speculated that the spots might be cancer, resulting from high levels of endocrine disrupters in the river.  Yingling passed on the email to StateImpact.
PFBC river biologist Geoffrey Smith says the commission has been studying the lesions, with help from the U.S. Geological Survey. In the meantime, Smith says the black spotted fish are also showing up in the upper Allegheny River, the Juniata River, F.J. Sayers Lake, and Pinchot Lake. Smith says previous pathology results from similar lesions indicated the spots were not malignant. But he’s unsure if that’s the case with this spring’s crop of fish.

And figuring out what the lesions are, may be easier than tracing the cause. Several contaminants enter the river from different sources. Smith writes that a 2009 analysis of fish tissue revealed “15 PCB congeners, 13 flame retardants, two personal care products, 14 organochlorine pesticides, and nine other pesticides and their respective break-down products.”
Despite continuing studies, Smith says it would be soon to come to any conclusions about the role of endocrine disruptors, or other contaminants, either alone or in conjunction with one another.
“While the presence of intersex is often the attention grabber, it is likely that these contaminants could have an immune suppression affect on these fish as well.  With the whole host of environmental stressors that the juvenile smallmouth bass are encountering at this point in time, distinguishing what factors are contributing to the mortality leaves us in a “chicken or egg” scenario.”
Smith says his department has also documented high levels of parasites and bacterial infections in the fish.

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