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Title: Effects of Gonadotropin-releasing hormone IIa dose on channel catfish (Ictalurus punctatus) ovulation

Author
item Quiniou, Sylvie
item Bosworth, Brian

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2020
Publication Date: 5/20/2020
Citation: Quiniou, S., Bosworth, B.G. 2020. Effects of Gonadotropin-releasing hormone IIa dose on channel catfish (Ictalurus punctatus) ovulation. North American Journal of Aquaculture. https://doi.org/10.1002/naaq.10151.
DOI: https://doi.org/10.1002/naaq.10151

Interpretive Summary: Production of channel catfish x blue catfish F1 hybrids by U.S. catfish farmers has increased dramatically in the last 15 years. However, hybrid catfish fry production requires hormone induced ovulation of female channel catfish and remains an inefficient process. Previously, scientists at the Warmwater Aquaculture Research Unit, USDA-ARS, Stoneville, MS demonstrated that a novel spawning aid, GnRH IIa given as 2 dose of 20/80 µ/kg of female body weight 16 to 24 h apart resulted in higher ovulation rates and more total fry production than salmon LHRHa and mammalian LHRHa, two spawning aids which are currently being used to induce ovulation at most commercial catfish hatcheries. In this study, the effects of lowering the dose of GnRH IIa from 20/80 µg/kg of female body weight to 5/20 µg/kg on ovulation and egg production was determined at three timepoints during the spawning season: early (May 1), middle (May 15) and late (June 5). The results indicate that the lower dose of GnRH IIa provided similar ovulation and egg production in comparison to the higher dose across the spawning season. Therefore, commercial hybrid catfish producers can likely substantially reduce their production costs by reducing the dose of GnRH IIa used to induce channel catfish females to ovulate while not negatively impacting egg production.

Technical Abstract: Production of channel catfish x blue catfish F1 hybrids by U.S. catfish farmers has increased dramatically in the last 15 years. However, hybrid catfish fry production requires hormone induced ovulation of female channel catfish and remains an inefficient process. Previously we demonstrated GnRH IIa given as a two dose (priming-induction) 20/80 µg/kg of female body weight, resulted in superior ovulation rates for channel catfish compared to salmon LHRHa and mammalian LHRHa, products currently used at commercial catfish hatcheries. The objective of the current study was to determine if GnRH IIa given at a quarter dose (5/20 µg/kg total) would give similar results to the full dose (20/80 µg/kg) and if response varied over the spawning season. Trials were conducted at 3 time points during the 2017 spawning season: early- (May 1), mid- (May 15) or late-season (June 5). At each time point, 20 females were injected IP with a full dose and 20 females were injected IP with a quarter dose of GnRH IIa. Data were collected for female weight, latency, incidence of ovulation and egg weight. No statistically significant differences were observed between quarter dose and full dose for latency, incidence of ovulation, egg weight and egg weight per kg of female body weight. The data indicate the quarter dose of GnRH IIa (5/20 µg/kg of female body weight) gave similar results to the full dose of 20/80 µg/kg. Additional trials are planned to confirm that the quarter dose gives similar results to the full dose at commercial hatcheries.