Reproductive cycle of Bolinus brandaris (Gastropoda: Muricidae) in the Gulf of Gabes (southern Tunisia)

The reproductive cycle of the purple dye murex (Bolinus brandaris) from the Gulf of Gabes was studied through gonad histology and calculation of bio-physiological indices (general condition index - K and gonadosomatic index - GSI). The shell length at first sexual maturity (SL50) of B. brandaris was also investigated using a macroscopic maturation scale. The population's sex ratio was statistically skewed (M:F = 1:1.5), with a significant dominance of females over males. Monthly variations in the maturation stages of gonads, K and GSI showed that B. brandaris has an annual reproductive cycle, a long period of gonadal activity and a slight asynchronicity between the sexes. The spawning season comprised the period between April and July, with a clear spawning peak from May to June. The SL50 was reached at 56.4 mm in females and 54.6 mm in males. Although at present B. brandaris has no commercial value in Tunisia, it is predictable to become a fishery-exploited species in the near future. The present data, particularly the timing and duration of the spawning season and the size of individuals of both sexes at first sexual maturity, provide baseline information to propose the early adoption of fishery management measures, aimed at ensuring sustainable exploitation and long-term preservation of this alternative fishing resource, once commercial exploitation of this species commences.We are grateful to the technical staff of INSTM (Centre of Sfax) for their assistance during field surveys and laboratory procedures. Thanks are also due to Mr. Tarek Rebai (Medicine University, Sfax) and Mr. Mohamed Salah Romtdane (National Agronomic Institute, Tunis) for their valuable help during histological analyses. Paulo Vasconcelos is funded by a post-doctoral grant (SFRH/BPD/ 26348/2006) awarded by the Fundação para a Ciência e Tecnologia (FCT - Portugal). Finally, the authors acknowledge the valuable comments and suggestions provided by two anonymous reviewers and by the Editor-in-Chief of Mediterranean Marine Science.publishe