MANIPULATION OF SPAWNING CYCLES OF CHANNEL CATFISH IN INDOOR WATER-RECIRCULATING SYSTEMS

Channel catfish Ictalurus punctatus were induced to spawn out of seaso n by means of photothermal and hormonal manipulations in indoor water- recirculating systems. Groups of fish were maintained under the follow ing temperature regimes: annual, cycles of 9 months in cool water (17 +/- 2 degrees C) followed by 3 months at spawning temperatures (25-28 degrees C); compressed, 6 months in cool water, then 3 months at spawn ing temperatures; annual-compressed, 6 months at spawning temperatures , followed by alternating cycles of 6 months of cool temperatures and 3 months of spawning temperatures; and extended, 15 months at cool tem peratures, then 3 months at spawning temperatures. At cool temperature s fish received light 8 h/d; at spawning temperatures they received li ght 14 h/d. Fish subjected to two successive compressed regimes consis tently spawned at the outset and at two 8-month intervals thereafter. All fish in the other groups also spawned when water temperatures were increased to 25 +/- 2 degrees C. Injections of luteinizing hormone-re leasing hormone analog and human chorionic gonadotropin were used with half of the pairings to achieve spawning success. Hormone-induced fem ales laid fewer eggs than females that spawned naturally either in sea son or out of season. Out-of-season fry production was similar to fry production from in-season spawns when eggs were collected and hatched in hatching jars. We demonstrated that manipulation of ovulation and o ocyte maturation can be achieved in channel catfish to potentially pro vide a stable, year-round supply of fingerlings.