DISTRIBUTION AND REPRODUCTIVE BIOLOGY OF THE SPINNER SHARK, CARCHARHINUS BREVIPINNA (MÜLLER AND HENLE, 1841) (CHONDRICHTHYES: CARCHARHINIDAE)

Abstract

The spinner shark, Carcharhinus brevipinna, is a Lessepsian immigrant formerly common in the Gulf of Gabes (southeastern Tunisia, central Mediterranean). It migrated northward into the Gulf of Tunis as a consequence of competition pressure from its sympatric species, the sandbar shark, C. plumbeus. Adult males and females reach over 1720 mm and 1960 mm total length (TL), respectively. The largest known male and female are 2630 mm and 2750 mm TL, respectively. There is no significant relationship of mass versus TL between males and females. C. brevipinna is a placental viviparous elasmobranch. Adult females have a single functional ovary and two functional uteri, in which encapsulated eggs and embryos are equally distributed. Mating occurs in spring or early summer; parturition, in August. Gestation lasts 13-14 months or longer, and there is a seasonal reproductive cycle. Vitellogenesis proceeds in parallel with gestation. Diameter of the largest yellow-yolked oocytes ranges from 31 to 36 mm (33.3 mm ± 1.4...