ANNAPOLIS-Lesions found this week on bait fish in tributaries of Baltimore County’s Middle River are puzzling biologists and prompting Maryland officials to advise Labor Day vacationers to exercise caution when swimming and fishing.
While biologists say they don’t believe the sores found on menhaden are due to Pfiesteria piscicida, the microbe in its non-toxic form was found in the water, said John Surrick of the state Department of Natural Resources. Pfiesteria, in its toxic form, has caused lesions and mass fish kills in the past.
“It is unclear what is causing the lesions on the menhaden,” Surrick said.
While scientists say they are concerned about the marks, they noted that other fish in the river, such as perch and anchovies, appear healthy.
Besides the lesions, the menhaden appear otherwise normal. When fish suffer from pfiesteria, they often behave erratically –swimming upside down for example, Surrick said.
Pfiesteria is a little known but potentially harmful microorganism that in its toxic state can kill a healthy fish in three minutes and cause serious health problems for people, according to the Chesapeake Bay Foundation.
In August of 1997, an outbreak of pfiesteria led to the death of thousands of menhaden, rockfish and croakers. Maryland officials closed the Pocomoke River and prohibited all fishing, swimming and personal watercraft use. More than two dozen people reported pfiesteria-related illnesses — ranging from rashes to memory loss.
Public health officials said there have been no reported illnesses associated with the Middle River so far this summer, but that people should exercise caution.
“Our advice to the public is to use common sense,” said Robert A. Venezia, of the Maryland Department of Health and Mental Hygiene. “Fish that look healthy are safe to eat. Don’t go swimming if you see dead and dying fish, and if you catch a fish with any kind of sore on it, throw it back.” Biologists plan to monitor the river closely. -30-