Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 15, 2008
Publication Date: February 9, 2008
Citation: Davis Jr, K.B., Bates, T.D. 2008. Temperature Cycles Induce Early Maturation in Channel Catfish. Aquaculture America Conference. 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. If the generation time could be shortened, genetic improvement could be achieved at a faster rate. 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. Channel catfish from the select USDA 103 fish were spawned in 2005. Three spawns were combined and divided in to two groups. One group was hormonally feminized with methyl testosterone, and was designated SR, and untreated fish were designated controls (C). Both groups were grown in the hatchery until October of 2005. Each group was then further divided into three environmental regimes. One C and one SR group were raised in the tanks (T) at 26 C the entire time, one C and one SR group were moved to outdoor 0.1 acre ponds, and a third group of C and SR fish were raised under an alternating thermal cycle of 2 months at about 12 C (designated W), followed by 4 months at about 26 C (designated S). This last group was designated the cycled group. Fish were fed when the temperature was warm enough for them to feed. When the fish were about 22 months old, the fish held in the ponds had been exposed to 2 summers and 2 winters, the fish held in tanks had only S temperatures, and the cycled fish had been exposed to three S periods and three W periods. 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. In late April thirty females from each group were placed in 0.05 hectare ponds with 20 male fish and 10 spawning cans. Males for the SR group came from their respective control group. At that time the T fish were significantly heavier than both the P and the cycled fish which were similar to each other. Beginning in mid-May the cans were checked for spawns twice a week. The first spawn occurred on May 24 in the Cycled Control group and by July 23, there had been 22 spawns from that group. There was only one spawn (June 4) from the SR cycled group, and only 3 spawns (June 28, July5 and July 20) from the P fish in the ponds. 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.