SANDSTONE - Deep beneath the surface of West Virginia's New River, a transmitter implanted into a fish's belly lets out a telltale beep.
"I've got a fishy!" said biologist Taylor Phillips.
Phillips has spent all spring and most of the summer listening for beeps. They tell her how far each of the transmitter-equipped walleyes has traveled from where she first captured it.
"The idea is to track the seasonal movements of New River strain walleyes," said Phillips, a fisheries technician for the state Division of Natural Resources. "We know Sandstone Falls is an important spawning area for them, but we don't yet know where they go after they spawn."
The picture still isn't complete, but it's starting to come into focus.
In late February, Phillips implanted sound-emitting "acoustic tags" into 20 walleyes, all captured from the river just downstream from the falls. After the spawning season ended, the fish began drifting downstream, most of them for miles and miles.
"A few of the fish made it as far downstream as Hawks Nest Lake, which is as far as they could go because Hawks Nest Dam acts as a barrier," Phillips said. "That surprised me. I expected them to migrate downstream; I didn't expect them to get all the way to Hawks Nest, but they did."
Most of the tagged walleyes strung themselves out like pearls along the 44 miles of river between Sandstone Falls and Hawks Nest. Phillips expects them to eventually migrate back upstream to spawn, but she isn't sure when the migration might begin.
"Right now, the fish seem to be hanging around in the areas they migrated to," she said.
To find the tagged fish, Phillips drifts downriver and dangles an omnidirectional hydrophone - a highly sensitive underwater microphone - off the boat's gunwale. Wearing headphones, she listens intently for beeps from the walleyes' tags.
"If I hear a beep, it usually means I'm within about 100 meters of one of my tagged fish," she explained. "When I get a strong beep, I switch to a directional hydrophone that allows me to pinpoint where the fish is."
Phillips logs each fish's tag number and GPS coordinates on a notebook. When a fish moves, she knows about it.
In addition to the live tracking she does three or four days a week, she also collects data from a network of six "passive" acoustic receivers submerged at strategic points along the river. When a fish passes near one of the receivers, a mini-computer inside the receiver detects the beep from its tag and logs the fish's tag number, the date and the time. To collect the data, Phillips snags the receivers' anchor cables with a grappling hook, hauls the units to the surface and downloads their accumulated information onto a laptop computer.