Insight on reproductive strategy in Portuguese waters of a commercial protogynous species, the black seabream Spondyliosoma cantharus (Sparidae)

摘要

Information on fish reproductive strategy is essential to understand population dynamics. Samples of black seabream, Spondyliosoma cantharus, were collected from the western Portuguese continental coast to investigate the reproductive cycle, the timing of spawning, length at maturity and sex change, fecundity type and fecundity. This species is a protogynous hermaphrodite, showing a sharped biased sex ratio towards females for lengths smaller than 25 cm, and significantly biased towards males above this value, with no females occurring above 35 cm. Development of secondary growth follicles was asynchronous, and it was estimated that each female spawns 27 batches during the spawning season, which takes place from February to May. Half of the females' population was mature at 18.41 cm and have changed sex at 25.62 cm. Sex change takes only a brief period of time, as transitional individuals were scarce and most showed oocytes regressing into cystic structures. The species presents a clear indeterminate fecundity type with massive atresia happening at the end of the spawning season. Mean values of 203 oocytes and 5431 oocytes by gram of eviscerated female were estimated for relative batch fecundity and relative annual fecundity, respectively.