Indoor rearing is becoming a reality
Stocking crappie into public waters is rarely needed, but some systems occasionally could benefit from adding fish to supplement weak year classes.
Hatchery production of crappie is presently limited to spawning wild-caught fish in hatchery ponds and rearing those fish to small fingerling size.
Their fish-eating habits make rearing crappie to larger sizes in hatchery ponds a difficult and expensive proposition. Also, the limited pond space is needed to spawn and rear other fishes, like Florida largemouth bass and catfish.
The solution is to spawn and rear the fish indoors.
Researchers at Lincoln University in Missouri have developed procedures for rearing wild-spawned crappie fingerlings to adult sizes on prepared feeds — like those used to grow catfish — in indoor tanks.
This breakthrough allows fast growth, year-round crappie rearing and the production of larger fish for stocking.
Rearing crappie on prepared feed also opens the door for private aquaculture operations to rear crappie for sale as food fish.
Needed to maximize the potential of these indoor operations is a year-round source of fry.
Research at Mississippi State University by Dr. Peter Allen and graduate student Charlie Culpepper has taken a giant step toward successful out-of-season spawning and tank culture of white crappie.
Out-of-season spawning requires rearing adult crappie in indoor tanks where water temperature and photoperiod — the hours of light and dark — can be manipulated.
Adult crappies are notoriously difficult to keep alive in tanks because they are prone to bacterial infections, they do not accept prepared feed and they often shun live minnows.
The MSU team found they could combat the disease problem by holding the fish in cool water (about 60 degrees) containing 3 to 5 parts per thousand sea salt (about 10 to 15 percent of ocean salinity) for the first two weeks after transfer from the wild to the lab tanks.
Adult crappy need good nutrition to develop healthy eggs and sperm, and be productive spawners. Allen and Culpepper used a highly controlled feeding regimen to train adult crappie to eat small koi carp and silver shiners.
With healthy adult crappie swimming in laboratory tanks, they began out-of-season spawning experiments.
The strategy was to expose the crappie to a brief winter and then “rush” them to spawning season.
Beginning in December, water temperature in the tanks was lowered to 50 degrees and day length was shortened to eight hours to simulate winter.
After two weeks of ‘winter,’ water temperature was gradually raised to 72 degrees and day length was gradually increased to 16 hours of light — conditions that resembled those when crappie naturally spawn.
The gradual transition to spring and spawning time lasted three weeks for one group of crappie and six weeks for another group.
The fish were then injected with hormones that stimulate the final development and release of eggs and sperm.
One female subjected to a three-week transition from winter to spring spawned, but the egg volume was small and fertilization of eggs was only 10 percent.
Two females subjected to a six-week transition spawned; one of these fish produced a large volume of eggs and fertilization rate was 32 percent.
The results of these initial experiments were far from 100 percent successful, but they were encouraging.
Allen and his students are now refining and testing new procedures to improve the amount of eggs and sperm produced and to increase the percentage of adult crappie that spawn out of season.
“Experiments conducted this year have resulted in egg production rates similar to those of wild-caught fish during the normal spawning season,” Allen reported.
The MSU researchers are also turning their attention to what will probably be the largest challenge — getting recently hatched crappie to accept prepared feed.
When Allen and his students solve that riddle, indoor culture of crappie will be a valuable tool to provide managers with any size of crappie at any time.
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