Reproductive biology of the bluntnose sixgill shark Hexanchus griseus (Bonnaterre, 1788) (Chondrichthyes: Hexanchidae) from the Mediterranean Sea: a review

Abstract

     Adult bluntnose sixgill shark (Hexanchus griseus) males and females from the Mediterranean were over 3000 mm TL. Size at birth was 556-680 mm TL. Ripe oocytes ranged 68 and 75 mm TL (mean 71.71±2.6) in diameter and 127-147 g (mean 134±8.4) in weight. The reproductive cycle lasted at least one year, but probably more. The chemical balance of development (dry weight of newborn pup/dry weight of ripe oocyte) was 3. One adult female contained 57 ripe oocytes; a second contained 100. Hexanchus griseus is probably able to live and reproduce in the Mediterranean Sea, however, further observations are needed to confirm that a sustainable bluntnose sixgill shark population has been established here, especially off the Maghrebin coast.