As T-shirt vendors hawked their wares and the curious made a detour from their Sunday morning coffee run, a small boat bobbed in Maryland's most famous pond, spraying the first batch of chemicals that scientists hope will kill the voracious northern snakehead.

State fisheries biologists gathered before dawn yesterday in Crofton, and spraying began just after 7 a.m. under the watchful eye of a media horde corralled along a wedge of shoreline by yellow police crime scene tape. The airboat moved slowly back and forth across the homely, nameless pond, the driver directing a stream of two herbicides from a 100-gallon tank into the water. At a pair of smaller ponds nearby, a similar operation was being carried out.

State officials say the chemical cocktail of diquat dibromide and glyphosate will kill all the oxygen-producing vegetation and suffocate a large percentage of the fish, including snakeheads. But because snakeheads have a primitive lung that allows them to breathe out of water, biologists will return after about a week to apply the fish poison rotenone to ensure eradication.

Steve Early, the Department of Natural Resources fisheries biologist in charge of logistics, said he was pleased with yesterday's three-hour operation.

"It pretty much came off as planned," he said.

The owner of the smaller ponds, who had initially blocked state access to his property, also said he was satisfied.

"We're happy that the state has taken these steps," said Crofton businessman William Berkshire, who watched the scene with his 8-year-old granddaughter. "This is what's best for the people of Maryland."

Given the fish's capability to breathe and slither short distances out of water, scientists worried that the snakeheads could wiggle 75 yards to the Little Patuxent River. But DNR fisheries chief Eric Schwaab said fish in laboratory tests didn't take a land-based escape route to avoid poisoning, and he doesn't think it's likely they'll make a break for it this time.

"We don't expect a mass exodus of fish from the pond," he said.

The No. 1 concern now, he said, is the possible stench from dying weeds and fish.

DNR employees will be skimming the pond daily and hauling off odorous material.

"We don't expect it to be overwhelming, but we're preparing for the worst," Schwaab said.

So marks the beginning of the end for the northern snakehead - Channa argus - the predatory pest from China that has become the most talked-about summer fish tale since Jaws.

Jay Leno made it the butt of jokes. Regis Philbin informed a television audience. And DNR employees became adept at live interviews with national and foreign reporters.

Surprisingly, no one capitalized on the snakehead's fame - until yesterday.

Within 100 yards of each other along Route 3, three enterprising Crofton residents sold T-shirts.

Steve Koorey, an unemployed bank manager, peddled "Crofton, Maryland Home of the Snakehead" shirts emblazoned with the head of a toothy, nasty-looking cartoon fish.

"Today's the day," he said, smiling and sweating profusely in the baking sun. "I only have a small window of opportunity."

Koorey gave one of his shirts to Joe Gillespie, the Crofton angler who caught the snakehead that tipped DNR that there was more than one predatory fish in the pond.