Feb 18, 2007 3 min read

HAGERSTOWN, Md. (AP) – A parasite that causes trout to swim in circles until they die has been found in two hatcheries in far western Maryland, prompting plans by state fishery managers to destroy 80,000 infected fish that would have been stocked in lakes and streams this year, an official said Thursday. The Department of Natural Resources will test for “whirling disease” in Maryland waterways that hold wild trout in hopes of learning how far the organism has spread, said H. Robert Lunsford, director of freshwater fisheries.

“We’ll do a pretty big effort when the swim-out fry emerge from gravel in late spring,” he said.

The problem was first reported Thursday by The (Baltimore) Sun.

The infected fish were discovered last month at the Bear Creek Rearing Station near Accident in northern Garrett County and at a contract trout-rearing operation at the Mettiki Coal Co. near Table Rock in southern Garrett County, Lunsford said.

As a result, 20 percent fewer rainbow and brown trout will be stocked this spring for anglers across Maryland to catch, Lunsford said. Last year, the state stocked 197 streams and ponds with 418,250 trout, the Sun reported.

The parasite, Myxobolus cerebralis, has long been known to exist in the Potomac River’s North Branch, which is about 20 miles from Bear Creek and several miles from Mettiki. Lunsford said it might have been spread to the hatcheries from mud on the feet of birds or bears.

The organism, which is not a risk to humans or other fish, deforms the spines and skulls of trout. It has decimated wild rainbow trout populations in the West and is now found in 22 states, according to the Whirling Disease Foundation.

The microscopic parasite was first detected in Maryland 12 years ago at a state trout-rearing station in the North Branch below the Jennings Randolph Dam near Bloomington. Lunsford said fish held there by submerged nets apparently had caught it from wild trout in the river.

The parasite lives in the skulls and spines of fingerling trout, warping their bodies, deforming their heads and blackening their tails. Fish that survive into adulthood shed millions of spores when they die. The spores are then eaten by tiny worms, which carry the parasites until they grow and infect fish.

The DNR said anglers can help stop the spread of whirling disease by not moving caught fish from one stream to another, not discarding fish carcasses in a stream or on a stream bank, and by removing mud from boots and equipment before moving from one stream to another.