The reproductive biology of the sandbar shark, Carcharhinus plumbeus (Chondrichthyes: Carcharhinidae), from the Gulf of Gabès (southern Tunisia, central Mediterranean)

The sandbar shark, Carcharhinus plumbeus, is commonly captured in the Gulf of Gabes (southern Tunisia). Of 932 specimens collected from January 2001 to May 2004, the smallest mature male was 1545 mm total length and the largest male was 1935 mm. All males above 1600 mm were mature. Adult females ranged 1660-2815 mm, while all females above 1720 mm were mature. The pupping season occurred in spring and early summer, with parturition in July. Gestation was estimated at twelve months, with females appearing to reproduce in alternate years. The diameter of the largest yellow-yolked oocytes ranged 29-32 mm (mean 30.3 plus or minus 1.2) with the mass ranging 9.1-13.3 g (mean 11.9 plus or minus 1.3). Both uteri were compartmentalized into chambers and a single embryo developed in each chamber. Length and weight at birth, based on near-term embryos, were estimated at 450- 650 mm and 532-1458 g. The chemical balance of development, based on the mean dry masses of the largest yellow-yolked oocytes and near-term embryos, was 40.3, showing that C. plumbeus is a matrotrophic species. Ovarian fecundity was slightly higher than uterine fecundity. There was a positive relationship between uterine fecundity and total length of females. Litter sizes ranged 4-10 (mean 6.9 plus or minus 1.1). Embryos and free-swimming juvenile and adult females significantly outnumbered males.Original Abstract: Pas trupan siljokrilac, Carcharhinus plumbeus, redovito se lovi u Gabeskom zaljevu (juzni Tunis). Od 932 primjerka, sabrana od sijecnja 2001 do svibnja 2004, najmanji zreli muzjak bio je dug 1545 mm, a najveci 1935 mm. Svi muski primjerci, duzi od 1600 mm, bili su spolno zreli. Odrasle zenke bile su duge od 1660 do 2815 mm, od kojih su one preko 1720 mm duzine, bile spolno zrele. Sazrijevanje se odvijalo u proljece i rano ljeto, s okotom u srpnju. Vrjeme nosenja je procijenjeno na 12 mjeseci. Zenke su se razmnozavale u izmjenicnim godinama. Promjer najvecih oocita (sa zumanjcem) iznosio je 29-32 mm (prosjecno 30,3 plus or minus 1,2) i mase 9,1-13,3 g (prosjecno 11,9 plus or minus 1,3). Uterusi su bili pregradjeni u komorice. U svakoj komorici razvijao se samo po jedan embrij. Duzina i tezina kod rodjenja, bazirane na embrijima priblizno iste starosti, procijenjene su na 450-650 mm i 532-1458 g. Kemijska ravnoteza razvoja, bazirana na srednjim suhim tezinama zrelih oocita i embrijima priblizno iste starosti, iznosila je 40,3 sto znaci da je pas trupan siljokrilac, Carcharhinus plumbeus,