Variability in reproductive performance of sex-reversed tilapia Oreochromis aureus

The reproductive performance of two O. aureus pseudofemale groups was studied in three successive breeding seasons. At the end of the first breeding season, the two initial groups of pseudofemales were divided in two new experimental groups, the first with pseudofemales spawning more than three spawns (HSR = High Spawning Rate pseudofemales), and the second with the other pseudofemales (LSR = Low Spawning Rate pseudofemales). In the first breeding season, the mean number of spawns was significantly higher with HSR pseudofemales (7.4 ± 2.7 spawns pseudofemale- 1) than with LSR pseudofemales (0.7 ± 1.0 spawns pseudofemale- 1). The splitting up increased significantly the number of spawns in the both HSR (12.1 ± 3.7 spawns.pseudofemale- 1) and LSR (2.1 ± 3.1 spawns pseudofemale- 1) pseudofemales groups. The LSR pseudofemales stopped reproducing in the third breeding, season but not the HSR pseudofemales (7.1 ± 3.8 spawns pseudofemale- 1). The splitting up did not affect the high percentage (36.3%) of no-spawning pseudofemales detected during the first breeding season. During the second breeding season, the absolute (1024 ± 507 eggs spawn- 1) and relative (4433 ± 2233 eggs spawn- 1 kg- 1) fecundity of HSR pseudofemales were higher than those of LSR pseudofemales (791 ± 426 eggs spawn- 1 and 3177 ± 1617 eggs spawn- 1 kg- 1, respectively). In the three successive breeding seasons, HSR pseudofemales produced 88.2% of spawns observed and 90.3% of eggs and fry collected. These data show that the reproductive potential in a group of O. aureus breeders depends on a few pseudofemales, those that have a high spawning capacity and a wide capacity of eggs production. This result suggests a scope to improve the spawning capacity in a line by studying the heritability of this reproductive trait in the successive generations of HSR breeders. (Résumé d'auteur