Reproductive biology of the blacktip shark, Carcharhinus limbatus (Chondrichthyes: Carcharhinidae) off West and North African coasts

Capapé C., Seck A.A., Diatta Y., Reynaud C., Hemida F., Zaouali J.

Date de parution: décembre 2004
Volume: 28
Number: 4
Pagination: 275-284
Editeur: Société Française d’Ichtyologie
doi: https://doi.org/10.26028/cybium/2004-284-001
Résumé

The blacktip shark, Carcharhinus limbatus, is commonly captured along the west coast of Africa and rarely in the Mediterranean, where it was recorded in the Gulf of Gabès (southern Tunisia). Following competition pressure from its sympatric species, the sandbar shark, C. plumbeus and the spinner shark, C. brevipinna, it migrated northward into the Gulf of Tunis and off the Algerian coast. Adult males and females reached over 167 cm and 178 cm total length (TL), respectively. The largest male and the largest female were 216 cm and 245 cm TL, respectively. They were no significant differences of relationship of mass versus TL between males and females. C. limbatus is a placental viviparous elasmobranch. Adult females had a single ovary and two functional uteri, in which encapsulated eggs and embryos were not equally distributed. Mating occurred in Spring or in early Summer, with parturition in July. Gestation lasted approximately one year. There is perhaps a biannual reproductive cycle. In some specimens, vitellogenesis proceeded in parallel with gestation. Diameter of the largest yellow yolked oocytes ranged from 23 to 25 mm (mean: 23.95 ± 0.80) and their mass from 5.9 to 8.4 g (mean: 7.48 ± 0.92). Both uteri were compartmentalised into chambers and a single embryo developed in each chamber. Size and mass at birth, based on fully developed embryos, and the smallest free-swimming specimens (neonates) were between 61-65 cm TL and 0.935-1.375 kg respectively. A chemical balance of development based on mean dry masses of the largest yellow yolked oocytes and the fully developed embryos was # 69. It was the highest value ever computed in a viviparous elasmobranch, and confirmed that C. limbatus is a matrotrophic species. Ovarian fecundity was slightly higher than uterine fecundity. There was a slight relationship between the two categories of fecundity and the females TL. Litter sizes ranged from 6 to 8. Among the embryos and the free-swimming specimens the females outnumbered the males ones. This was not the case for the adults.

Mots-clés: Carcharhinidae - Carcharhinus limbatus - MED - Reproductive biology - Western African coast
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