Reproduction of the sawback angelshark Squatina aculeata (Chondrichthyes: Squatinidae) off Senegal and Tunisia
Reproduction of the sawback angelshark Squatina aculeata is presented with specimens captured off Tunisia (central Mediterranean) and off Senegal (eastern tropical Atlantic). The smallest adult male and adult female were 120 and 137 cm total length (TL), respectively, and weighed 12.7 and 22.0 kg, respectively. Above 122 cm TL for males and 143 cm TL for females, all the observed specimens were adult. The largest male and the largest female were 152 and 175 cm TL and weighed 24.0 kg and 32.0 kg, respectively. Males and females presented similar total length versus total mass relationships, although the latter were considerably heavier than the former. Size at birth was between 30.3 and 35.0 cm TL and mass at birth between 276 and 325 g. The two ovaries and the two uteri were functional. Ripe ovarian follicles ready to be ovulated ranged between 76 and 85 mm in diameter and weighed between 200 and 237.6 g. Gestation lasted one year approximately, but ovarian follicles growth blocked at the beginning of gestation. However, ovarian follicles growth started again before embryos were at mid-term gestation. This is a new case of semi-delayed vitellogenesis typical of Squatina spp. A biannual reproductive cycle remains a suitable hypothesis. A calculated chemical balance of development based on dry masses of ripe follicles and full-term embryos was # 0.66 and showed that S. aculeata is a purely lecithotrophic species as other studied squatinid species. Ovarian fecundity ranged from 12 to 22 and is higher than uterine fecundity, which ranged from 8 to 12. Both categories of fecundity were slightly related with females size. The sex-ratio was 1: 1 in embryos. The subadult males significantly outnumbered the female ones. This was not the case for juveniles, adults and for the total sample.