The importance of thermoperiod for proper gametogenesis and successful egg and sperm production in meagre (Argyrosomus regius) breeders in aquaculture

We examined the effect of constant water temperature throughout year on gametogenesis, spawning success and egg/sperm/embryo quality in meagre (Argyrosomus regius). Two broodstocks were exposed to simulated natural photoperiod, andeither attenuated seasonal (SeasT, 16.4 19.6ºC) or relatively (CoT, 19.4 ± 0.6ºC).In period (May), 4 couples per group induced spawn with gonadotropin releasing hormone agonist (GnRHa). Gonadal stage development, sperm parameters plasma levels sex steroids evaluated prior GnRHa treatment. Spawning egg/sperm over following weeks. Constant did not prevent but exposure inclusion winter low was beneficial both sexes. The mean (±SD) diameter largest vitellogenic oocytes administration significantly higher SeasT compared CoT (598 27 vs 520 17 μm). Testosterone females group, all other hormones similar spawned more consistently relative fecundity, 24-h embryo survival produced eggs. A pronounced negative observed males, since males exhibited a spermiation index 0 treatment, latter clearly having study demonstrated that do undergo gametogenesis significant extent even under temperatures during year. However, thermal regime -even an one- necessary for proper development gametes, allowing successful induction using established protocol.