PINE BLUFF (AGFC) – Black lights and phosphorescent fish – throw in your standard mod Peter Max poster, some Hendrix on the turntable and maybe a lava lamp, and it would seem like someone’s living room circa 1970. However, more than four decades later, black lights are less a living room showpiece and more useful in the hands of biologists looking for “glowing” crappie to determine how effective a pond-stocking program can be.
As part of a grant administered by the Arkansas Game and Fish Commission, Greyson Farris, a master’s student in the aquaculture program at the University of Arkansas at Pine Bluff, is studying the AGFC’s crappie stocking program using fingerlings from two hatcheries: the Joe Hogan hatchery at Lonoke and the William H. Donham hatchery in Corning. Late in the fall of the past two years, about 180,000 fingerlings – half of them white crappie from Lonoke and the other half black crappie from Corning – were treated with chemicals that allow researchers to track the fish after stocking in eight Arkansas lakes, according to JJ Gladden, a biologist at the Lonoke facility.
During the first year, the fish were marked with the U.S. Department of Agriculture-approved oxytetracycline, or OTC, in which the fingerlings absorb in a six-hour bath. The chemical is absorbed in bony areas such as the ear bone. Last fall, the fish were also treated with OTC, but Farris then used another marking agent, calcein, a phosphorescent dye, in another, shorter treatment before the fingerlings were taken for stocking.
The key difference between using calcein over OTC is that fish tested for the presence of the marker do not have to be sacrificed in the process.
“As far as I know, nobody has ever done the calcein marking with crappie,” Farris said. “They’ve done it with largemouth bass, perch, walleye.”
Fish captured for testing that were marked with only OTC have to be cut open for their ear bone, or otolith, to be examined under special light. The nature of calcein, Farris says, is that it’s absorbed not only in the bones but in the fins, around the eyes and mouths, and it offers a vivid green appearance when seen under black light and with specific glasses. Using the calcein as a marker required the AGFC to request a special license from the U.S. Fish and Wildlife Service, but the process for marking the fish was far easier, Farris said. Instead of a six-hour soak in OTC, the fingerlings were hit with a 30-second bath of salinized water (about 40 parts per 1,000, he said), a fresh water rinse, then a seven-minute soak in the calcein-water mixture. The salt water bath drew out most of the water from the fingerlings – making them “sponge-like,” Farris said – which then soaked up the calcein.
OTC is a proven method in marking fish, in use for more than 40 years, Farris said. The question is, how long will the calcein last in a crappie? Farris said calcein in fish has been shown to degrade over time in sunlight. However, crappie tend to stay deeper in lakes and the fish’s nature is to not turn on its side; the underbelly of the crappie should be least likely to see much if any photodegradation, Farris said. And in fish he’s tested both at UAPB and in pond nettings, he’s found calcein.
All this is to show how effective a stocking program can be for a lake such as Lake Saracen in Pine Bluff, one of the eight lakes in Farris’ study. Other lakes in the study are Lake Des Arc, Lake Charles, Lake Poinsett, Calion Lake, Irons Fork Reservoir, Sugarloaf Lake and Beaverfork Lake. So far, he has found growing crappie that were AGFC-stocked in six of the lakes. “It’s great to see how many fish are surviving on a month-to-month scale,” Farris said. “Most of the time when you stock ponds or lakes, you don’t know if you’re having a benefit to the Commission unless you have a creel survey or stocked fish come up into your nets. You have to kill the OTC fish, and that’s not beneficial in the long term. Also, every OTC-marked fish will take 15 minutes of lab time, at least, to check. You can tell immediately if you have a calcein-marked fish. Fisheries biologists are better off in the long run, getting it cheaper, faster and easier.”
Calcein marking costs more, about $5,000 to mark 90,000 fish compared to $1,000 for OTC. But the tested fish live. And, “any measure of a stocking program is a measure of success,” Farris notes.
Because of warmer autumns the past two years, the fingerlings weren’t ready for the treatment and stocking until November. Farris tested the lakes through the winter and said he will resume through the summer and fall, netting about 250 crappie per lake to find if they were part of the stockings.
“The objective was to find a way to look at these fish without having to kill them, stock them, see them in the nets with [black lights] and see if they were the fish we stocked,” Farris said.