Snakeheads in Potomac contract virus that threatens largemouth bass


A snakehead fish is caught in Little Hunting Creek near Mount Vernon, Va. (Larry Morris/Associated Press)
August 13, 2013

Northern snakeheads in the Potomac River have apparently contracted a virus that is known to cause massive kills among largemouth bass, the U.S. Geological Survey announced Tuesday.

But that doesn’t mean the pathogen, known as largemouth bass virus, will negatively affect snakeheads, an invasive, predatory fish species from Asia. Snakeheads pulled from two Potomac tributaries in Virginia by biologists were healthy, despite carrying the virus.

But the virus could make the snakehead more dangerous to bass, said Luke Iwanowicz, a USGS research biologist who led the study of the fish, published recently in the Journal of Aquatic Animal Health.

Iwanowicz said it is possible that snakeheads could be reservoirs of the virus and pass it to bass throughout the Chesapeake Bay watershed.

So far, the virus has been detected in bass, sunfish and other species, the USGS said, but only largemouth bass have developed a disease as a result. Most bass who contract it are otherwise fine, but some have trouble submerging and are forced to float on the surface.

Scientists aren’t sure about the origin of the largemouth bass virus or how it spreads.

It was first reported in Florida in 1991. Four years later, it was cited as the cause of a massive fish kill at the Santee Cooper Reservoir in South Carolina, according to a fact sheet on the Web site of Bassmaster, a sport fishing outfit that pays close attention to all things related to the fish.

According to Bassmaster, the virus also was blamed for a fish kill in Lake George on the border of Indiana and Michigan. Illinois biologists detected it in fish from four lakes and in hatchery stock.

Most Virginia waters tested with low infection rates in 2001, but by 2011 the virus was in “all sixteen bodies of water tested statewide and major rivers except the tidal James River,” the USGS said.

The virus was detected in snakeheads as part of a joint survey by the USGS and the Virginia Department of Game and Inland Fisheries to detect pathogens introduced by snakeheads in Virginia’s waters.

Biologists describe the species as a fierce predator that was likely introduced into the Chesapeake Bay watershed in Virginia and Maryland and has spread as far north as New England and as far south as Florida.

“Efforts to eradicate or control the spread of this invasive fish have been unsuccessful so far, and scientists predict that the northern snakehead is likely to increase its present range,” the USGS said.

Darryl Fears has worked at The Washington Post for more than a decade, mostly as a reporter on the National staff. He currently covers the environment, focusing on the Chesapeake Bay and issues affecting wildlife.
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