1a.Objectives (from AD-416):
Development of spawning aids or hormone delivery methods to improve the efficiency of channel x blue hybrid catfish embryo production.
1b.Approach (from AD-416):
Conduct spawning trials to assess the effective peptide analog or hormone delivery methods to induce maturation and ovulation in channel catfish and also to measure the associated physiological responses to the treatments.
Hybrid catfish, a cross between channel catfish and blue catfish is a superior fish with higher production potential in commercial ponds. Nevertheless, hatchery production of hybrid catfish embryos has been a severe bottleneck for decades. Evaluation of mammalian luteinizing hormone releasing hormone analogs (LHRHa) to induce ovulation in channel catfish to produce hybrid catfish in commercial hatcheries has expanded substantially in the last 5 years. There is a need to reduce the cost of hybrid fry production in hatcheries by a potent ovulating hormone to improve the efficiency of hybrid catfish fry production. ARS researchers at the Warmwater Aquaculture Research Center at Stoneville, MS, are working to improve the efficiency of hybrid catfish embryo production through better control of ovulation and stripping of high quality eggs in channel catfish. A synthetic spawning hormone, salmon gonadotropin releasing hormone analog (sGnRHa) presently marketed as OvaRH by Western Chemicals, WA, was tested in a spawning trial. The minimum effective dose was determined to be 10 ug OvaRH/Kg body weight to induce maturation and ovulation in channel catfish. Holding the broodfish in soft mesh bags reduced the confinement stress and improved the reproductive performance. Plasma estradiol levels peaked at 24 h post hormone injection to signal the maturation process in the fish prior to ovulation. The results of the study were repeated in three commercial hatcheries with limited number of fish. Our results prompted Western Chemicals, Inc. to sponsor OvaRH for INAD exemption in 2012. In 2012 spawning season, three spawning trials were conducted with mixed age groups of channel catfish with our recommended dose of OvaRH to produce hybrid catfish embryos. Four commercial hatcheries conducted 20 trials (43 to 97 fish per trial) with 1,600 channel catfish females with 10 ug OvaRH/Kg BW to induce spawn channel catfish to produce hybrid catfish fry in catfish hatcheries. OvaRH was more efficacious than mammalian LHRHa in one hatchery and comparable in other three hatcheries. Catfish hatcheries reduced their hormone costs by 50% by administering OvaRH to induce spawn channel catfish. Improved broodfish handling procedures and hormone delivery methods to improve the efficacy of OvaRH in hatchery production are presently addressed.