GREENVILLE – Anglers, don’t be alarmed if you catch a trout with an antenna coming out of its belly. It’s just a “robo-trout.”

About 75 transmitter-equipped trout have been released in Moosehead Lake and its tributaries by the Maine Department of Inland Fisheries and Wildlife as part of an effort to track them and maintain the right mix of fish.

Three of them have been caught by anglers, including Ken Snowdon, who nabbed one of the unusual fish back in January.

The trout Snowdon plucked from the icy waters was a trophy fish that was 23 inches long and weighed 51/2 pounds. It also had a thin, 10-inch antenna protruding from its orange-red belly that was transmitting a signal.

The Department of Inland Fisheries and Wildlife let Snowdon keep the fish but not before retrieving the $200 transmitter.

The fish, sans transmitter and antenna, won first place in a fishing derby and it’s being mounted at a taxidermist shop in Harmony.

Only large, mature fish captured in live traps are selected for the program. Local anglers came up with the robo-trout moniker.

“We do the surgery right out in the field,” said Tim Obrey, a fish and wildlife biologist. “We implant the transmitter and wire, give ’em three or four stitches and they’re ready to go.”

The transmitter-equipped trout have been swimming since last fall. Biologists can track the fish via receivers carried by hand, planted in fixed locations or taken aloft in airplanes. A computer logs each time a receiver picks up a signal.

By the time Snowdon’s fish was caught on Jan. 28, its signal had been tracked from Cowan Cove past Kineo Mountain over to the Moose River, then south past Big Dry Point into the middle of Moosehead Lake and finally to Doughnut Cove.

Snowdon put in a special request to the taxidermist for his special catch. He asked Jayne Leslie Dyke to use a line of dark thread to mimic the antenna that was protruding from its belly.

Once it’s mounted, it’ll look like it did when Snowdon caught it, with the antenna-like thread coming from a small incision.

“It will be a conversation starter, that’s for sure,” he said.