Enhancement of oogenesis/spermatogenesis in meagre Argyrosomus regius using a combination of temperature control and GnRHa treatments

Abstract

A multiple GnRHa injection method for inducing spawning of high fecundity and quality in meagre was optimized. Specifically, the study (a) examined how long females would continue spawning in response to consecutive, weekly GnRHa injections, if maintained at the natural spawning temperature, and (b) evaluated whether males can produce adequate amounts of good quality sperm for the same period, with the assistance of a GnRHa therapy. Combined with stable temperatures (19–20°C) that are prevalent during the early spawning season (April–May) in the Mediterranean Sea, each weekly GnRHa injection induced ~2 consecutive spawns per week for a period of 17weeks. Fish spawned consistently 2days after treatment and produced high fecundity and egg quality (i.e. fertilization, hatching and early larval development). Maximum mean total fecundity (±S.D.) obtained was 1,415,000±149,000eggskg−1 in 32 spawns, being the highest total season fecundity reported for meagre, and significantly higher than the estimated maximum potential fecundity for the species. At the same time, sperm of consistently high quality (i.e. initial motility, duration of motility and storage survival) was produced in response to treatment with multiple GnRHa implants, though towards the end of the experiment a significant reduction (ANOVA, P≤0.05) in spermatozoa density was observed. This protocol is expected to enhance greatly commercial production of meagre. Statement of relevanceThe present study reports on an optimized protocol for the induction of consistent and repeated spawning in meagre, based on the use of weekly GnRHa injections combined with stable temperatures that are prevalent at the early spawning season in the Mediterranean Sea. This protocol produced eggs of high fecundity and quality (i.e. fertilization, hatching and early larval development) for a period of >4months, and it is expected to enhance greatly commercial production of meagre.