Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: June 24, 2008
Publication Date: August 1, 2008
Citation: Davis Jr, K.B. 2008. Temperature Cycles Induce Early Maturation in Channel Catfish. Global Aquaculture Advocate. 11:70-71 Technical Abstract: A major impediment in improvement of channel catfish by selective breeding is that a high percent of fish do not spawn until the third year. The conditions that lead to sexual maturation in fish have not been established. Size, nutritional state and number of seasonal cycles have all been suggested as regulating maturation. Three spawns from 2005 were combined and exposed to one of three environments. One group was maintained in indoor tanks supplied with flowing well water held at 26 C and fed to satiation daily. A second group was raised in outdoor ponds and fed when the temperature was warm enough to allow feeding. The third group was held in indoor tanks and the temperature was regulated so that the fish were held at 26 C for four month then changed to about 12 C for two months. This group had the annual temperature change functionally shortened by six months, and were fed daily during the warm period and twice a week during the cold periods. When the fish were about 22 months old, the pond raised fish had been exposed to 2 cold periods and the temperature cycled fish had been exposed to 3 cold periods. In April 30 female fish and 20 male fish were placed in spawning ponds with 10 spawning cans. At this time fish raised in the tanks were about twice the size of fish in the ponds and those on a shortened temperature cycle. Fish were sampled at the end of each thermal cycle. Body weight, gonadal weight, liver weight and a blood sample were taken from 10 males and 10 females in each group. Beginning in mid-May the cans were checked for spawns twice a week. The first spawn occurred on May 24 in the temperature cycled group and by July 23, there had been 22 spawns from that group. There were only 3 spawns (June 28, July5 and July 20) from the fish raised in ponds, and only one poorly developed spawn was collected from the fish raised in tanks. These data suggest that the number of seasonal cycles is more important than size in determining the time required to reach maturity, and that shortened seasonal cycles can induce early maturation.