Paired spawning with male rotation of meagre Argyrosomus regius using GnRHa injections, as a method for producing multiple families for breeding selection programs

Weekly gonadotropin-releasing hormone agonist (GnRHa) injections were used to induce spawning in paired male and female meagre (Argyrosomus regius) with a weekly rotation of the males, in order to produce a large number of families, as a method to facilitate selective breeding programs. Two different broodstocks were used (HCMR and IRTA), with females of mean weights of 11.7 ± 2.6 kg and 20.0 ± 1.8 kg, and males of 10.2 ± 1.2 kg and 15.1 ± 1.0 kg, respectively. A single GnRHa injection of 15 μg kg−1 was administered to each selected female, and 7.5 or 15 μg kg−1 to each male to induce spawning. In the subsequent weeks, maturity was checked and fish were induced as above, but males (n = 18) were rotated to form a different pair with the selected females (n = 21). Experiments finished when all paired combinations had been completed or a fish lost maturity status and could not be induced further. A total of 56 families were produced with a mean number of eggs from each family of 87,666 ± 11,244 eggs kg−1. There was a decline in the fecundity, number of spawns and percentage of pairs that spawned successfully after consecutive weekly GnRHa injections. Relative fecundity declined significantly from 134,495 ± 25,557 eggs kg−1 female body weight after the first injection, to 44,252 ± 17,638 eggs kg−1 after the fourth injection. However, there were no differences amongst weeks in egg fertilization success, hatching success or larval survival to 5 days post hatch. The decrease in fecundity and spawning success was attributed to a loss of maturity observed in the females, which may be related to differences in mate selection strategies between male and female meagre. The study demonstrated that paired spawning with male rotation was a successful method that can be used for breeding programs to produce a limit of three families per female or as a scaling up step to produce large numbers of offspring from a limited number of selected pairs.