HARRISBURG, Pa. – Following recent reports from anglers that some smallmouth bass caught in the Susquehanna River have had irregular black blotches, the Pennsylvania Fish and Boat Commission (PFBC) today 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 PFBC 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 are most often found on the head, lips, tail or fins. Melanin is a black pigment in the skin cells of fish and this condition is often 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,” said Shiels. “While the appearance of these spots may be alarming, there is no harm to human health from consuming these fish.”
He added that 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); the Allegheny River (1999); and in the 1980s in Conneaut Lake (Crawford County), Presque Isle Bay (Erie County), Raystown Lake and several other waters. 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.
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 through the website www.fishandboat.com/bassproblems.htm.
Blotchy Bass Condition
Fact Sheet
Characteristics
• Blotchy Bass Condition (also known as melanosis) is characterized by the appearance of irregular shaped black blotches resembling black ink spots. It is caused by an increase in melanocytes (black pigment cells) in the skin. Blotches typically occur on the lips, head, tail and fins. The condition is normally observed in larger adult fish (12 inches) and has been documented to affect up to 25% of a population at a given time. There are several diseases and conditions that affect the skin coloration of fish. However, it is important to note that in fish exhibiting the blotchy bass condition the discoloration will not be raised or inflamed. Bass exhibiting the blotchy bass characteristics appear to be healthy and there has been no known mortality associated with the condition.
• There is no known cause of the condition. It is thought to be related to environmental, growth or genetic factors.
• It has not been linked to general water pollution or specific pollution events.
History
• The Pennsylvania Fish and Boat Commission has documented this condition in the Susquehanna River (2012, 2011, 2006); Cowanesque Lake, Tioga County (2003); Allegheny River (1999); Sugar Lake, Crawford County (pre-1999); Lake Wilhelm, Mercer County (pre-1999); Conewago Lake, Lebanon County (1989); Raystown Lake (1988); Presque Isle Bay, Erie County (1986, 1987); and Conneaut Lake, Crawford County (1980, 1981, 1982, 1985).
• The blotchy bass condition was studied in bass in the Hudson River estuaries starting in 1983.
• In 1986 a nationwide inquiry resulted in the condition being documented in 12 states including PA, NY, DE, and MD.
Consumption
• Blotchy bass condition is limited to skin discoloration and presents no human health or fish consumption concerns.
