"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.