EVALUATION OF MACROSCOPIC MATURITY ANALYSIS WITH HISTOLOGY IN THE DIGYNIC PROTANDROUS HERMAPHRODITE WHITE SEABREAM DIPLODUS SARGUS SARGUS (PISCES, SPARIDAE)

Gonads of 111 individuals of a digynic protandrous hermaphrodite fish species, white seabream (Diplodus sargus sargus), were sampled along the coast of NW Sicily (southern Tyrrhenian Sea). Theses gonads were analyzed to evaluate a macroscopic maturity scale widely used in fisheries studies, through histological examination of the gonadal tissue, to observe the microscopic morphological features. A 5-phase microscopic classification scale was produced based on macroscopic staging for both males and females. A mismatch was found between macro and microscopic sexing due possibly to the difficulties met in correct sex identification of bisexual individuals. Likewise a mismatch was found between macro and microscopic reproductive phase identifications. Partial matching was detected between the two analysis methods as regards the monthly occurrence of different reproductive phases, with a peak of spawning capable individuals in spring. Gonadosomatic index and sea surface temperature were used along with reproductive phases to describe the reproductive cycle on a monthly basis. The seasonal trend of gonadosomatic index followed closely that of reproductive phases, showing a peak in spring preceded and followed by consistently low gonad weight. Despite the small sample size, microscopic validation of a macroscopic reproductive phase evaluation proved useful to identify the weaknesses of the latter method and widened the knowledge on reproductive biology of white seabream in the Tyrrhenian Sea.