Effects of implantation of different GnRH hormone dosages and DHA Selco supplementation on induction of sexual maturation of non-breeding season of grouper (Plectropomus leopardus Laepède, 1802)

Abstract

This study was conducted with two experiments to evaluate the effectiveness of applying two methods to promote early maturation of grouper Plectropomus leopardus, including GnRHa hormone implantation and DHA Selco supplementation in the feed of immature fish in the off-spawning season. Experiment 1 was designed with 4 treatments of three doses of GnRHa hormone (25, 50, 70 µg/kg) and a control treatment. Experiment 2 was arranged with 1 experimental treatment (with DHA Selco supplementation in the feed) and 1 control treatment (without DHA Selco supplementation). Both experiments were carried out by using a completely randomized design (CRD). The results showed that stimulating grouper Plectropomus leopardus with GnRHa hormone implantation promoted maturation time earlier than normal, with a maturation rate >40%. However, stimulation at doses of 25 or 50 µg/kg reduced the rate of larval deform compared with that at 75 µg/kg. Supplementation of the polyunsaturated fatty acid DHA in the feed combined with stimulation with the hormone GnRHa at a dose of 50 µg/kg promoted early maturation time by up to 70%, achieved a spawning rate of 87.5% and improved the survival rate of 5-day-old larvae.