GAINESVILLE, Fla. - Few people in this country know more about the sharp-toothed Asian fish that has invaded a Crofton pond than the man some here call Dr. Snakehead.

For the past year, Walter R. Courtenay Jr. has pored through reams of papers in a trailer in the Central Florida woods to assess the risk of the snakehead to native fish species.

Today, the 68-year-old ichthyologist will join a dozen other scientists on Maryland's recently formed snakehead panel to discuss how to get rid of the fish - known for its tendency to devour other species, move on land and survive out of water for several days. It's been multiplying feverishly in a pond behind a Dunkin Donuts along Route 3, and experts worry it could get into nearby waterways.

Though Crofton is the first place that a northern snakehead has been found to have spawned in this country, Courtenay believes it won't be the last.

"Can you imagine all the things we don't know about?" he asked in an interview in his lab this week. "That's the really scary part."

Concerned about snakehead sightings in a few spots around the country, the government brought Courtenay out of retirement last fall to work on the snakehead study at the U.S. Geological Survey's Florida Caribbean Science Center. The Florida Atlantic University professor emeritus returned to a familiar and collegial lab that he had visited many times in his 40-year career.

The lab is the sort of place where scientists wear fish shirts, display fish-inspired cartoons below fish nameplates on their doors (Courtenay's is a snakehead), and send ill co-workers fish-covered get-well cards. It's not the kind of place that usually fields calls from reporters or sees its research mentioned on late night comedy shows.

Courtenay, who owns about 70 fish shirts himself, doesn't mind the attention he and the snakeheads are getting. Nor do his colleagues.

"It's good for the issue. Unfortunately it takes some sort of exotic invasion to bring this home to people," said fishery biologist Amy Benson. "I wish we didn't have these jobs, but somebody's got to look into this stuff."

Experts say Courtenay is the right person for the job.

"In North America, he's about as good as it gets," said Robert G. Howells, a fishery research biologist with the Texas Parks and Wildlife Department who worked with Courtenay when snakeheads were discovered in Houston fish markets last year.

Courtenay, who is working with two other scientists, James Williams and Leo Nico, said the snakehead study is a first for the government. "Someone realized there was a small segment of the aquarium fish trade that was selling snakeheads and some of them had been turned loose by fish owners," Courtenay said.

The report is due next month.

Last year, Courtenay and his team began e-mailing others in the "fish net" - an informal group of biologists who trade information - to see what they knew. He already knew the snakehead could survive out of water for three days, walk on its fins, and eat voraciously. But he soon learned 25 species -such as bull's eye and northern - live from the Yangtze River in China to as far north as Siberia. Many Asian cultures ascribe healing powers to the fish. Folklore has it that snakehead oil is used to prevent scarring after C-section operations.

Because it is illegal to buy a snakehead in Florida, team members searched for snakeheads in Asian markets while on vacation in Missouri and New York where they are legal. They asked colleagues to keep their eyes peeled.

They bought a bull's eye snakehead online from Rhode Island. Buster, a northern snakehead, arrived from a colleague in Boston. Williams bought Ollie, another northern snakehead, from a fish market in Orlando. The salesman, who told Williams that Ollie was a "very special catfish," recently had a not-so-friendly visit from fisheries agents.

Courtenay concluded that the northern snakehead - the species found in Crofton - was the most dangerous because it can live from the tropics to Siberia.

"We're talking cold," he said. "That fish can live anywhere it wants to in the United States."

But that point was largely academic at the time: Even though one northern snakehead had been caught in a California reservoir in 1997, and two had been caught in the St. Johns River in Orlando in 2000, the fish generally could only be found in tanks in Asian markets.