It's almost certainly a bowfin - a species that has prowled the depths of Mountain State waters since before the last Ice Age.

"We've gotten calls from people who think they have caught snakeheads, but really what they had caught were bowfins," said Scott Morrison, a district fisheries biologist for the state Division of Natural Resources. "We've never had a confirmed sighting of a snakehead in West Virginia."

Maryland and Virginia fisheries officials have been trying to eradicate snakeheads in tributaries of Chesapeake Bay, where the species has become established. Authorities became aware of the species in 2002 when a fisherman caught one from a pond in Crofton, Md.

Maryland law enforcement officers discovered that a local man had purchased two adult snakeheads from a New York market and had released them into the pond. The pond was drained and the snakeheads were destroyed, but the incident put officials on high alert.

A 2004 search found an established population of snakeheads in the Potomac River between Great Falls and the Chesapeake Bay. Fisheries experts believe the fish are restricted to that single stretch of river by the presence of the falls upstream and the salinity of the bay downstream.

Even so, West Virginia officials have been on the lookout for snakeheads ever since. If the species ever gets established upstream from Great Falls, it could then migrate upstream into West Virginia's Cacapon and South Branch rivers.

As awareness of snakeheads has increased, so have reports from anglers who believe they might have caught them.

Morrison said all those fish turned out to be bowfins. To help fishermen distinguish snakeheads from bowfins, DNR officials had a graphic created, and have posted the graphic on the agency's website.

"The easiest way to tell the two species apart is to look at the anal fin - the long, non-paired fin on the fish's underside," Morrison said. "In the snakehead, that fin is very, very long. It's more than half the length of the dorsal fin, which is also very long.

"On the bowfin, the anal fin is much shorter, much less than half the length of the dorsal."

Anal fins aren't the only distinguishing characteristics. Male bowfins have an easily seen eye-like spot on their tails. Snakeheads don't. Bowfins' heads are rounded like a trout's, while snakeheads' are pointed and flattened like a muskellunge.

The two species' pectoral and pelvic fins - the paired sets of fins on the fish's undersides - also differ from one another. The bowfin's are on opposite ends of the belly, like a trout's, while the snakehead's are bunched closely together like a bluegill's.

Morrison said he became familiar with snakeheads as a young man growing up in Thailand.

"I had a snakehead as a pet," he said. "When I heard snakeheads had been found [in the Potomac watershed], I figured they were tropical and would just die out. But the species here is native to China and Korea, and can stand low water temperatures."

Both species can grow quite large. The longest bowfin ever caught in West Virginia measured a little over 32 inches. The heaviest weighed 91/4 pounds. Snakeheads sometimes grow a little longer, but usually don't weigh quite as much.

Both species feed voraciously on smaller fish. While Maryland and Virginia authorities are worried that snakeheads might upset their streams' ecological balance, Morrison said bowfins pose no such threat.

"Bowfins have been here all along, and they're a part of our ecosystem," he said. "If they haven't caused any problems by now, they probably aren't going to."

Reach John McCoy at 304-348-1231 or johnmc...@wvgazette.com.