May 08--Jimmy Johnson stood with a scalpel poised above the square of his patient's belly exposed under surgical drapes. An assistant, monitoring respiration and heart rate, deemed vital signs "fast but good."
As Johnson made a 2-centimeter incision, more anesthetic was delivered -- not via IV or gas, but an oversized syringe squirting drug-laced water onto the patient's gills.
Johnson is a resident veterinarian with the Chicago Zoological Society and his patient, a nine-and-a-half-pound female muskie, was about to have a radio transmitter implanted in her abdomen to help Forest Preserves of Cook County biologists study how fish use the preserves' lake habitat.
Veterinarians with the Chicago Zoological Society, which manages Brookfield Zoo, implanted transmitters in half a dozen muskies, walleye and largemouth bass at the Forest Preserves of Cook County's McGinnis Field Station in Orland Park Thursday.
Since all the county's forest preserve lakes are man-made, some don't provide the kind of habitat where fish will thrive, said Chris Anchor, the Forest Preserves of Cook County's chief wildlife biologist.
"We study what areas they're using and which they aren't using to see if we can improve the lakes to benefit the fish," he said.
The transmitter program has been going on for more than a decade and forest preserve staff typically track fish and map the areas they're found in two or three times per week, Anchor said.
If there are sections fish aren't using, they'll put in man-made structures that mimic underwater vegetation and create variety, he said. Better habitat means healthier fish, higher reproductive rates and stronger fish populations, he said.
For walleye, which struggle to reproduce in forest preserve lakes on their own, tagged fish also act as "Judas fish," Anchor said.
Before the breeding season, forest preserve staff capture female walleye to strip them of their eggs, which are then hatched and allowed to grow in a forest preserve rearing pond before being released into preserve lakes. Forest preserve staff follow transmitter-equipped fish to figure out where they're likely to catch the female walleye, Anchor said.
Each fish operated on Thursday, taken from Busse Lake near Elk Grove Village, was netted and placed in a tank with anesthetic-laced water until it was sedated. Veterinarians then measured and weighed each fish before placing it belly-up on a v-shaped surgical trough, making a two-to-three centimeter incision and sliding the transmitter -- a small cylinder carrying the radio transmitter chip with a thin wire antenna protruding -- into place.
After each fish was stitched back up, it was taken to the "recovery tank" for identification tagging and a blood draw before the anesthesia wore off.
Chicago Zoological Society senior staff veterinarian Jennifer Langan, also a clinical associate professor at the University of Illinois College of Veterinary Medicine, said Thursday's procedures appeared "very successful."
Forest Preserves of Cook County biologist Daryl Cooper said the six fish will eventually be released back into Busse Lake, but Langan said they'd need to recuperate for two to three weeks first.
The transmitters will send out signals for more than a year, but even after the batteries die, they'll remain in the fish as it's more complicated to remove them, she said.
With each transmitter weighing only about 1 to 3 percent of the fish's body weight, the fish don't seem to mind being left with the extra hardware, she said.
"They take quite well to the transmitters," Langan said.
lzumbach@tribpub.com
