Reproduction of hatchery-produced meagre Argyrosomus regius in captivity II. Hormonal induction of spawning and monitoring of spawning kinetics, egg production and egg quality

TitleReproduction of hatchery-produced meagre Argyrosomus regius in captivity II. Hormonal induction of spawning and monitoring of spawning kinetics, egg production and egg quality
Publication TypeJournal Article
Year of Publication2013
AuthorsMylonas, CC, Mitrizakis N, Castaldo CA, Cerviño CP, Papadaki M, Sigelaki I
JournalAquaculture
Volume414-415
Pages318 - 327
KeywordsArgyrosomus regius, Egg quality, GnRHa implants, Induced spawning, Meagre, Reproduction
Abstract

The present study aimed at the development of an effective and efficient hormonal spawning induction method for meagre Argyrosomus regius, using controlled-release delivery systems loaded with gonadotropin-releasing hormone agonist (GnRHa). Three sets of spawning induction experiments were undertaken in the course of three years. In experiment 1, group spawnings were performed at different times during the reproductive period, in order to determine the most appropriate time for hormonal induction of spawning. Experiment 2 described in more detail the spawning kinetics of individual females induced to spawn at different times during the season, in order to obtain important information on spawning kinetics, batch fecundity and total fecundity in response to the hormonal treatment. In experiment 3, two similar broodstocks were used to obtain further production characteristics and monitor variations in egg/larval quality over the spawning period. The effective GnRHa doses used were 55-84μgGnRHakg-1 body weight in males and 46-92μgGnRHakg-1 in females. In general, successful spawning induction was achieved between early May and early June. Implantation with GnRHa induced spawning 2-3d after treatment and produced an average (±SD) of 12±5 spawns per broodstock or female over 3weeks, most of them over consecutive days. Batch fecundity was extremely variable (mean of 6631 to 104,409eggskg-1), with the largest batches occurring 3-4d after treatment, and very low fecundity after 1week from GnRHa treatment. As a result, the first 4 spawns of all spawning induction experiments constituted a mean of 75±13% of the total relative fecundity. Overall mean total relative fecundity was variable at 380,780±167,577eggskg-1. Evaluation of the ovaries after the cessation of spawning, demonstrated that the females still contained large numbers of oocytes in full vitellogenesis, and it is hypothesized that these fish could spawn further in response to a second GnRHa implantation. Fertilization success was very high in all spawning induction experiments, with the overall mean being 89±5%. Similarly, the produced eggs were of very high quality, based on the survival of the eggs during embryogenesis (>95%), hatching success (>99%) and larval survival 5d after egg collection (>87%), resulting in an overall larva survival of 73% of the total number of eggs spawned. These studies demonstrate that the GnRHa implants are an effective and efficient method for the induction of spawning in meagre, leading to the production of eggs of high fecundity and quality. © 2013 Elsevier B.V.

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