Black Spots on Susquehanna River Smallmouth Bass

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Pennsylvania’s Fish and Boat Commission (PFBC) recently released information in response to reports from anglers that smallmouth bass in the Susquehanna River sometimes exhibit black spots on their body.

The agency noted that blackish spots have been previously observed on bass from other waters in the state and that the spots do not appear to harm the fish. According to PFBC, the spots are limited to skin discoloration and 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 condition, known as melanosis, blotchy bass, or black spot, can appear as irregular black spots on the head, lips, tail or fins. Melanin is a black pigment found in the skin cells of fish.

PFBC biologists have previously documented black spots on bass in the Susquehanna River (2011, 2006); Cowanesque Lake, Tioga County (2003); the Allegheny River (1999); and in the 1980s in Conneaut Lake (Crawford County), Presque Isle Bay (Erie County), Raystown Lake and several other waters.

Black spots on bass were 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.

Because of the previous disease issue with juvenile smallmouth bass resulting in multiple poor year classes, the PFBC has placed catch and release regulations on all smallmouth and largemouth bass on portions of the Susquehanna and Juniata rivers and on their tributaries to a point one-half mile upstream, with a closed season from May 1 through June 15.

The regulations apply to approximately 32 miles of the Juniata River, from the State Route 75 Bridge at Port Royal in Juniata County downstream to the mouth of the river at Duncannon, Perry County. On the Susquehanna, the regulations cover 98 miles, from the inflatable dam near Sunbury in Northumberland County downstream to the Holtwood Dam in York County.

Anglers who observe sick fish or other unusual conditions can report it to the PFBC website:

source: Pennsylvania Fish and Boat Commission