Reproductive biology of the milk shark Rhizoprionodon acutus (Rüppell, 1837) from the Gulf of Suez, Red Sea, Egypt

The milk shark, Rhizoprionodon acutus (Rüppell, 1837), is one of the most abundant shark species landed at Ataka fishing port at the Gulf of Suez. A total of 357 individuals (165 males and 192 females) were collected from the trawl and artisanal fisheries. Males ranged from 44.6 to 88.5 cm TL, while females ranged from 47.8 to 97.2 cm TL. The total sex ratio was estimated at 1:1.16 for males and females respectively. Lengths at 50% maturity were estimated to be 76.5 cm TL for males and 74 cm TL for females. Females possess one functional ovary and two functional uteri. The vitellogenesis and gestation occur concurrently and thus females seem to have a reproductive cycle of one year with no resting period. The mean embryo lengths in different months and the presence of neonates in virtually all months, however, indicated that parturition takes place throughout the year with a peak in summer. Length and weight at birth, depending on term embryos and neonates ranged from 39.5 to 44.6 cm TL (mean 42.05 ± 2.55). Ovarian fecundity ranged from one to nine (mean 5.56 ± 0.33). Uterine fecundity ranged from one to six embryos (mean 3.22 ± 0.24). The sex ratio of embryos was approximately 1:1.