Evaluation of Short-Term Exposure to High Temperature as a Tool to Suppress the Reproductive Development of Channel Catfish for Aquaculture

Abstract

Short-term exposures to elevated temperatures reduce germ cell numbers in the gonads of some fishes, suggesting that heat treatment may be a viable method for delaying or suppressing reproductive development in cultured fishes. The objective of this study was to determine the effects of high temperatures on early gonadal development in channel catfish Ictalurus punctatus. Twenty-three-day-old (after hatching) channel catfish were exposed to temperatures of 27°C (control), 34°C, and 36°C for 4 weeks. Groups of 250 fry were placed in individual 152-L glass aquaria with external biofilters, and four replicated aquaria were used per temperature treatment. Water temperature was regulated with submersible heaters. At the end of treatment, body weight and standard length were measured in 30 individuals per aquarium and gonads were examined histologically in 10 individuals of each sex per aquarium. For statistical analysis, the unit of replication was the aquarium, and differences between treatments were considered significant at α < 0.05 by one-way analysis of variance (ANOVA) and Duncan's multiple-range test. Exposure to 34°C reduced oocyte size in ovaries and testicular size (cross-sectional area) and slightly decreased body weight but not standard length. Exposure to 36°C significantly reduced ovarian and testicular size, and 52% of females seemed to lack germ cells and may have been sterilized. However, exposure to 36°C also greatly reduced body growth and caused spinal curvatures and kidney abnormalities, suggesting that 36°C impairs the general health and growth of catfish fry. The results of this study are consistent with the concept that heat treatment can be used to manipulate reproductive development in channel catfish. Further research is needed to establish the appropriate combination of temperature level and treatment duration so as to reduce or eliminate germ cells without adversely affecting somatic growth during the period of treatment.