New data on the reproductive biology of the Atlantic weasel shark, Paragaleus pectoralis (Chondrichthyes : Hemigaleidae) from the coast of Senegal (eastern tropical Atlantic)

摘要

The Atlantic weasel shark, Paragaleus pectoralis (Garman, 1906), is the only species of the genus Paragaleus to be recorded off the western coast of Africa. It is commonly landed at the fishing sites along the Senegalese coast. Adult males and females are mostly captured in spring and summer. The smallest male and female adults were 810 mm, and 900 mm total length (TL), respectively. The largest male and the largest female adults were 1.32 m and 1.38 m TL, respectively, and weighed 7.55 kg and 11 kg, respectively. There was no significant difference for total mass and TL relationship between males and females. Mating occurred from March to May, and parturition in May and June. Gestation lasted approximately one year. Females had biennial or triennial reproductive cycle. Vitellogenesis did not occur while females were pregnant. Diameter of the largest yolky oocytes ranged from 25 to 31 mm (mean: 28.6 +/- 2.6) and their mass from 8.8 to 9.9 g (mean: 9.4 +/- 0.5). Both uteri were compartmentalized into chambers, with a single embryo in each chamber. Size and mass at birth, based on near-term embryos were between 390-500 mm TL and 214-407 g, respectively. A chemical balance of development based on mean dry masses of the largest yolky oocytes and the fully developed embryos was 14.8. Ovarian fecundity was slightly higher than uterine fecundity. There was a slight positive correlation between uterine fecundity and female TL, not between ovarian fecundity and female TL. Litter sizes ranged from two to seven (mean: 4.6 +/- 1.6) with males outnumbering females.