The day dawned cloudless, plump with possibilities for the fearless sportsmen.

They had heard the tall tales about the fish that walked and had jaws like a crocodile. Some had seen the TV movie, in which the crazed fish on growth hormones feasts on human flesh. One man had caught the real thing in the Potomac River and stared into the cold, vacant eye of the enemy. Now he was back for more.

"I'm here! I'm the snakehead slayer!" shouted Steve Picott, 40, of White Plains as he bounded up to the registration table at Marshall Hall boat launching facility last weekend, pumped for the start of the snakehead fishing tournament.

It was the second contest of the summer aimed at depleting the number of northern snakeheads in the Potomac and its tributaries. Since May anglers have reeled in close to 20 snakeheads in the river or nearby streams.

Scientists and recreational fishermen worry that the Asian import could tear through native species of fish and damage an important ecosystem. Environmental officials are not certain whether the snakeheads have established a breeding population in the Potomac or were released individually by pet owners. Smithsonian Institution scientists are testing DNA samples in an attempt to find out.

"We have made light of the snakehead in these tournaments, but [the fish] really does have the potential to wreak havoc if it does get out of control," said Robert Glenn, executive director of the Coastal Conservation Association of Maryland, which hosted the Aug. 28 event in Charles County.

At the first Snakehead Roundup last month, 130 fishermen hit the waters, but no snakeheads were caught. This tournament drew a smaller crowd: about 20 fishermen on eight boats. The first prize for the largest snakehead was a chartered fishing trip for four on the Chesapeake Bay. The rules were simple: Use any technique you want, and call if you catch one.

Out on the water, the sun burned off the giddiness, and Don Gardiner and Ken Hastings sorted out their strategy. Both were longtime fishermen but had no experience with the snakehead.

They headed for Dogue Creek on the Virginia side, where snakeheads have been found, and cast amid downed trees into the shoreline shallows. They experimented with different lures: spinners and crankbait and top-water poppers. Talking was kept to a minimum to maximize their luck. Blue herons flapped lazily over the boat, and bald eagles watched from the treetops, but whatever snakeheads were out there played coy.

"Working on getting skunked here," said Gardiner, a retired firefighter from Waldorf who works at Dick's Sporting Goods part time to support his fishing habit.

"I've got a stick of dynamite here somewhere," joked Hastings, an electrical engineer for a defense contractor and a resident of Mechanicsville.

Anglers, like golfers, have a high tolerance for failure. Since nothing was doing in Dogue Creek, the fishermen motored back across the river to try Greenway Flats and Bryan Point. After a few more hours, the men not only had no snakeheads but had no other fish either. Hastings kicked his sandaled-feet up onto the cooler and declared: "I'm ready to take a nap."

By 11 a.m., as the contestants hauled out their boats and ambled up to the post-tournament barbecue, each time the story was the same. Any snakeheads? Nope. Nah. Nothing.

Despite the result, the participants said they were pleased to have had a day of fishing and the opportunity to draw attention to the snakehead infestation.

"The snakeheads are terrible," said Bill Curry of Lusby, who owns a construction company and is active with the Coastal Conservation Association. "They could be very destructive. Within 20 years, I think it's going to decimate the bass population."

Although there was a shortage of the alien fish on this day, there was no shortage of lore. "Captain" Mike Starrett, who runs fishing trips with Indian Head Charters, said the snakehead grows to be four feet long. When it does, populations in addition to bass are at stake.

"Poodles beware if they get that big," he said.

Westley Moot stays in the boat as James Cantu, not shown, drives it out of the Potomac on Saturday at the northern snakehead hunt.No northern snakehead was snared, but Moot caught catfish at the tournament sponsored by the Coastal Conservation Association.Steve Carle, a member of the Southern Maryland Chapter of the Coastal Conservation Association, cooks hamburgers at the tournament.