Following recent reports from anglers that some smallmouth bass caught in the Susquehanna River have had irregular black blotches, the state Fish and Boat Commission recently confirmed that similar spots have been previously observed on fish from other waters in the state and that the spots do not appear to harm the fish.
The commission added that because the spots are limited to skin discoloration, the fish are safe to consume under the state's general fish consumption guidelines.
"The condition is commonly known as 'blotchy bass' or 'black spot' and has been documented occasionally in various Pennsylvania waters since as early as 1980," said Andy Shiels, PFBC deputy director of operations. "In fact, in 1986, a nationwide survey found that the condition was present in 11 other states, including N.Y., Delaware and Maryland."
The PFBC started hearing from anglers late last year concerning the black spots, which most often are found on the head, lips, tail or fins. Melanin is a black pigment in the skin cells of fish and the condition often is referred to by fisheries scientists as melanosis.
"It's not precisely known what causes the condition, but the bass that our biologists examined in previous years were generally healthy and in good condition," Shiels said. "While the appearance of these spots may be alarming, there is no harm to human health from consuming these fish."
He added the condition has not been linked to specific pollution events nor is there any evidence to suggest that blotchy bass condition is related to the young-of-year smallmouth disease issues in the Susquehanna River and some of its tributaries that the PFBC and other agencies have been studying since 2005.
PFBC biologists have documented the blotchy bass condition previously in Pennsylvania in the:
Susquehanna River (2011, 2006);
Cowanesque Lake, Tioga County (2003);
It also was observed in New York's Hudson River during the 1980s, which resulted in a N.Y. fisheries biologist surveying other states about the condition. The survey showed that the condition was present in largemouth and smallmouth bass in 12 states in the east, south and along the Gulf Coast.
PFBC biologists who have previously observed this condition indicate that it often occurs during the cold-water period of fall, winter and early spring and it appears to affect only fish larger than 12 inches. It typically occurs in a localized area and not uniformly in a lake or throughout a river system. Some bass have had one or two spots while others have had a dozen or more.
Anglers who observe sick fish or other unusual conditions can report them to the PFBC through the website www.fishandboat.com/bassproblems.htm.