In the infant sport of snakehead fishing, everybody has a theory about what makes the toothy creature bite.

There are debates about bait: green or orange plastic worms? What about spinners? There are disagreements about the best spots on the Potomac River, though Dogue Creek and Little Hunting Creek on the Virginia side seem to be the most popular.

And finally, there is the it-doesn't-matter school.

"It's like barracuda," said angler Richard Remele, 70, of Severna Park. "It has big teeth, and it eats just about anything."

All camps were represented yesterday at the 2004 Snakehead Roundup, which organizers billed as the country's first tournament for pursuit of the northern snakehead.

The event was held at Columbia Island Marina on the Potomac, which has emerged as a major haven for snakeheads. Sixteen have been caught this year in the Potomac or its tributaries.

The northern snakehead, a native of China and Korea, feeds voraciously on other fish and can wiggle short distances over land. It first appeared in this area in a Crofton pond in 2002, then began showing up in the river this year. Authorities are not certain whether the snakeheads are breeding in the Potomac or have been dumped there separately.

This month, six northern snakeheads were caught in a pond in Philadelphia. Pennsylvania authorities have submitted DNA to the Smithsonian Institution to see whether their snakeheads are related to the Potomac fish.

Organizers said yesterday they wanted to increase awareness of the hazards of nonnative species in general, warning people not to release pets, live bait or food fish into the wild.

"The snakehead is becoming the ugly poster child for the national campaign" to eradicate invasive species, said Benjamin Grumbles, who heads the Environmental Protection Agency's national water program.

Whatever its high-minded purpose, yesterday's event was at heart a fishing tournament. Accordingly, there were guys in mesh-backed gimme caps, a boat was raffled off, and beer was consumed before 10 a.m.

The major players in the snakehead fishing world were there, such as Clifford Magnus of Waldorf, who in June caught the biggest snakehead yet, two feet long and weighing nearly six pounds.

Tom Woo of Fort Belvoir, who caught three snakeheads in 10 days earlier this month, brought his wife, Myong, and three daughters.

"When he's trying to catch bass," explained daughter Emily, 6, "he catches snakeheads."

Most of the 130 anglers who registered for the roundup are bass fishermen. Some said yesterday that they feared the snakehead would eventually encroach on the Potomac's famous bass grounds.

Jim Howard, a tournament bass fisherman from Waldorf, called the Asian fish "a terrible thing."

"It's going to eat up my pets," he said, meaning the bass.

When the roundup officially started yesterday morning at the marina near the Pentagon, Howard and many other anglers roared off to the south, past Old Town Alexandria and under the Woodrow Wilson Bridge.

Howard then turned his boat into Little Hunting Creek, an inlet near Mount Vernon where three snakeheads have been caught this year.

For about 45 minutes, Howard repeatedly cast his lure to the edge of an underwater grass bed. All around him, boats full of anglers did the same, hoping that a snakehead would strike out from the shallows.

Finally, Howard's line bent and a fish flashed in the murky water.

He reeled it in: a two-pound largemouth bass. Normally, Howard would be happy to get it, but not today.

"Dammit," he yelled to another boat. "It's a bass."

When the roundup ended at 11:30 a.m., it was the same story for everybody: The anglers had caught bass, bluegill and perch, plus a bag of Doritos and a can of Old Milwaukee.

No snakeheads.

Magnus said later that he had seen a couple of snakeheads in the water, and the fly on one angler's line was bitten right off. Perhaps a snakehead was responsible, she said.

But that was all. None of the theories on snakehead angling had worked.

Afterward, some of the fishermen said they would keep trying. Woo said he would be out on Dogue Creek again that very afternoon.

James L. Frye, whose Marina Operators Association of America helped stage the event, said he believed the roundup had been a success even without any snakeheads. But he said he hoped there would be no need for another one next year.

"I would hope the species would be eradicated by then," Frye said. "If not, then yeah, we'll certainly call attention to it again next year."

Tom Woo, who caught three snakeheads this month, tries again with help from his wife, Myong, and three daughters.Participants hear rules before what organizers hope will be the only snakehead tournament.