In this study we evaluate whether the pattern of spatial variability of the macro-epiphyte assemblages of leaves of Posidonia oceanica differed in relation to anthropogenic interference in the Gulf of Gabes (southern coast of Tunisia). A hierarchical sampling design was used to compare epiphytic assemblages at 5 m depth in terms of abundance and spatial variability at disturbed and control locations. The results indicate that the biomass and mean percentage cover decreased at locations near the point of sewage outlet in comparison to control locations. These losses were related to the distance from the source of disturbance. This study revealed that the diversity is reduced in disturbed locations by the loss of biomass and the mean percentage cover, explained by means of a multiple-stressor model which plays an important role in the macro-epiphytes' setting. It is urgent to propose the best management plans to save the remaining P. oceanica meadow in the Gulf of Gabes and its associated epiphytes.

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The reproductive biology of the smooth-hound shark Mustelus mustelus was studied in the Gulf of Gabe`s (southern Tunisia). Females were found to mature between 1075 and 1230 mm total length (L T ) whereas males matured between 880 and 1120 mm L T . The L T at which 50% of the population reached maturity was 971 and 1172 mm for males and females, respectively. Male gonads were symmetrical in terms of mass and both functional, whereas in females only the right ovary was functional. The seasonal changes in the oocytes and testes development, embryo length and the occurrence of near-term and post-partum females showed that this species displayed a clearly defined annual reproductive cycle with parturition occurring during late April and early May, after a gestation period of 10-11 months. Mating took place during May and early June and fertilization occurred from early June to early July. The embryo sex ratio was not significantly different from unity. Litter size varied from four to 18 embryos and was positively correlated with maternal L T . The young were born with a L T of 340-420 mm.