DOGUE CREEK, Va. -- With the boat throttle in one hand and a portable antenna in the other, John Odenkirk zeroes in on the pinging sound in his headphones.
Unseen but definitely heard is one of 20 northern snakeheads fitted with small radio transmitters that emit sounds like sonar in a World War II movie. It is fish No. 0024, which, at about 12 inches, is one of the smaller of the bunch.
Odenkirk, a Virginia Department of Game and Inland Fisheries biologist, adjusts his headphones and leans over the side.
"Right there," he says, grinning and pointing at a pile of branches hard by a dock with cabin cruisers tied to it. "Oh, man, he's blowing my ears off."
Instead of dropping a fishing line over the side, Odenkirk marks down the GPS coordinates, the water depth and temperature, then motors away, listening intently for another ping.
Faced with a congressional mandate to "contain and eradicate" the invasive species nicknamed "Frankenfish," Maryland and Virginia biologists are trying to pinpoint where it lives and how quickly it reproduces.
The number of reports from recreational fishermen this year indicates that the voracious predator is breeding and growing at prolific rates in Potomac River tributaries such as Dogue Creek.
Last weekend, anglers reported catching snakeheads in the Anacostia River near Bladensburg in Prince George's County and in Mattawoman Creek in Charles County.
"The bottom line is, we're not going to eradicate them, so we've got to figure out how to control them," Odenkirk says.
In mid-April before spawning season, biologists implanted in 20 fish radios slightly larger than a paper clip and capable of transmitting their positions for up to a year. Odenkirk and his partner, Steve Owens, say they hope the pings lead them to where snakeheads have their young. Then, they will overlay locations on a map to show habitat, water temperature and depth.
The torpedo-shaped fish with camouflage markings made national headlines in 2002 when a fisherman hooked an 18-inch snakehead in a tiny pond in Crofton. Jon Stewart did jokes on Comedy Central, hawkers sold T-shirts with the fish's toothy profile and Interior Secretary Gale A. Norton called it "like something from a bad horror movie."
Maryland officials blasted the pond with poisonous chemicals, killing hundreds of snakeheads, and the federal government quickly banned importation and transportation of snakeheads.
