Effective Dose of Salmon GnRHa for Induction of Ovulation in Channel Catfish

Abstract

The present study was conducted to determine the minimum effective dose of salmon gonadotropin-releasing hormone analog (sGnRHa) to stimulate ovulation in Channel Catfish Ictalurus punctatus. Four doses of sGnRHa—0, 10, 15, and 25 µg/kg body weight (BW)—were compared with the commonly used dose of 100 µg/kg BW of mammalian luteinizing hormone releasing hormone analog (mLHRHa) to induce spawning in Channel Catfish. Hormone-induced catfish yielded significantly higher levels of plasma estradiol and ovulation success than saline-injected control fish. Ovulation ratio, relative fecundity, and number of fry per kilogram with 10 µg sGnRHa/kg were lower than those treated with 15 and 25 µg. To further refine the sGnRHa dose, spawning trials with 3- and 4-year-old Channel Catfish were compared using doses of either 10, 15, or 20 µg sGnRHa/kg BW. The relative fecundity (8,322 eggs/kg BW) and fry production (2,533 fry/kg BW) were higher in fish from the 15-µg sGnRHa/kg BW treatment. Hence, the results of this study suggest that 15 µg sGnRHa/kg BW is the minimum effective dose comparable with widely used mLHRHa to induce spawning in Channel Catfish and produce hybrid (Channel Catfish × Blue Catfish I. furcatus) embryos in hatcheries.

Received March 22, 2017; accepted July 12, 2017Published online September 5, 2017

ACKNOWLEDGMENTS

The author acknowledges Carl D. Jeffers for his technical assistance during the conduct of the study. The author also thanks Brian Peterson for estimating estradiol and cortisol concentrations in blood samples. Jim Brackett of Western Chemical, Inc., is acknowledged for providing the hormones and the sponsorship of the INAD to evaluate their use in catfish hatcheries. This study was funded by the U.S. Department of Agriculture (USDA), Agricultural Research Service under project number 6066-31000-012-00 D. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. The USDA is an equal opportunity provider and employer.