Cliff Magnus has glimpsed the future of the Potomac River, and it's an ugly sight: "It was totally covered in slime that was dripping off it like spaghetti sauce."

Magnus, 44, a woodworking artist and avid fisherman from Waldorf, was referring to the feared northern snakehead, a predatory fish native to Asia that has infiltrated Potomac waters and threatens to disrupt one of the region's most important ecosystems.

Nine snakeheads have been caught in a 14-mile span of the Potomac River and its tributaries -- from Little Hunting Creek on the Virginia side down to the Mattawoman Creek in Charles County -- and some scientists have become convinced that the fish has established a breeding population.

Magnus's experience with the snakehead only feeds the fish's oversize reputation.

On June 17, he was practicing for a bass tournament on Little Hunting Creek, a Potomac inlet near Mount Vernon in Fairfax County, when he spotted an unusually large bulge of water pushing through the lily pads in the shallows near a bulkhead. He cast his soft plastic Sinko lure at the bulge. The fish took the bait, and the fight was on.

"He ran me around the boat four or five times," Magnus said. The fish plunged under the boat and nearly wrapped the fishing line around the motor. His fishing buddy, Don Jenkins, asked him whether he had a mudfish on the line. But when Magnus pulled it out, he knew.

"The second I saw it I knew right away what it was," he said. "I said, 'That's exactly what [the Maryland Department of Natural Resources] did not want to find: a full-grown snakehead."

Full grown, indeed. It was two feet long and weighed close to six pounds, making it the largest snakehead caught in the Potomac. Magnus tried to kill the fish by repeatedly bashing it over the head with a pair of pliers. When it didn't die, he kept it out of water under the sun and called the Department of Natural Resources.

By the time an environmental official arrived at his home to collect the snakehead, a fish known for its ability to breathe air and scurry short distances over land, it had been out of the water for more than four hours, he said.

"I gave it to him alive; I let him deal with it," he said. "It was wrapped up in a plastic bag and still flopping when he walked away."

Magnus and other area fishermen have serious concerns about the potential for the snakehead to damage the prime largemouth and striped bass fisheries in the Potomac.

Bill Bennington, 42, who frequently drives 80 miles from his home in Baltimore County to fish from the Sweden Point Marina in Charles County, was toweling off his 18-foot bass boat after an outing last week where he caught 11 bass. But with the arrival of the snakehead, he was worried how long such a bounty would last.

"It's scary, it really is. I've heard they can really devastate a river," said Bennington, who fishes in professional bass tournaments and wore a T-shirt that read "Eat. Sleep. Fish."

"If they get established, they'll eat everything in their path."

Not all scientists agree that the snakeheads are definitely reproducing in the Potomac. DNA testing is being done at the Smithsonian to determine whether any of the fish caught are related. But to others, the many indications of a population -- the frequent catches in a wide swath of river, the varying ages, the female snakehead that was found full of eggs -- are proof enough.

"You look at the facts we've got, and you've got to draw the conclusion that they've been reproducing for some time," said John Odenkirk, a fisheries biologist at the Virginia Department of Game and Inland Fisheries. "The biomass is at such a point that they're starting to pop up."

Officials say there is no way to eliminate snakeheads from the Potomac, so they are relying on recreational fishermen to help limit whatever population exists.

The Department of Natural Resources plans to hold a snakehead fishing tournament this month and is offering "Snakehead Wrangler" hats to anyone who hauls one in. The Bass Pro Shops Outdoor World at Arundel Mills in Hanover also is involved, offering a snakehead reward -- gift certificates from $10 to $50 depending on the length of the fish -- for any snakehead brought to the store before the end of October.

"We recognize the tremendous sport fishery in the Potomac River and the detrimental impact of the snakehead," said promotions manager Larry Ellis. "We'd like to eliminate as many of them as possible."

Cliff Magnus, a die-hard fisherman from Waldorf, holds the huge snakehead he caught June 17 in Little Hunting Creek on the Virginia side of the Potomac.Magnus tried to kill the snakehead by keeping it out of the water and under the sun, but it wouldn't die.The snakehead caught by Cliff Magnus was the largest fished from the Potomac River. It measured two feet long and weighed almost six pounds.