Temperature effects on gonadal and somatic growth in channel catfish
Byerly, Michael Todd
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The purpose of this study was to examine the effects of elevated sub-lethal temperatures on the development of gonadal germ cells as well as somatic growth of channel catfish fry Ictalurus punctatus Current methods of enhancing growth in fishes require the use of chemicals or the long-term maintenance of genetically selected or modified brood stocks Exposing juvenile or adult fish to elevated sub-lethal temperatures has been shown to reduce or eliminate gonadal germ cells in some species. In this study. 23-day-old channel catfish fry were exposed to temperatures of 27 (control), 34. and 36°C for a period of four weeks. The results indicate that exposure to 34°C reduced oocyte numbers and testicular area with a slight decrease in overall body weight Exposure to 36°C resulted in a significant reduction in oocyte number and ovarian and testicular area. Also, 52% of females in 36°C treatment lacked germ cells in their gonads and thus may have been sterilized. However, the 36°C treatment impaired fish growth during the treatment period and caused spinal curvatures and enlarged kidneys The results of this study support the potential of heat exposure to reduce or completely eliminate gonadal germ cells in channel catfish More research is needed to develop a precise combination of exposure temperature and exposure duration so it may be possible to reduce or eliminate gonadal germ cells without adversely affecting somatic development. Also, future research should determine if a decrease in energy required for gonadal development is redirected towards somatic development.