Life history of the silvertip shark Carcharhinus albimarginatus from Papua New Guinea

Abstract

Growth and maturity of the silvertip shark Carcharhinus albimarginatus from Papua New Guinea were estimated to form the basis of future population assessments. Samples were collected from commercial longline vessels targeting sharks in the Bismarck and Solomon Seas. A total of 48 C. albimarginatus—28 males (95–219 cm total length, TL) and 20 females (116–250 cm TL)—provided data for the analyses. Employing back-calculation techniques accounted for missing juvenile length classes and supplemented the sample size. A multi-model framework incorporating the Akaike information criterion was used to estimate growth parameters. The von Bertalanffy growth function (VBGF) provided the best-fit growth estimates. Parameter estimates were L0 = 72.1 cm TL, k = 0.04 yr−1 and L∞ = 311.3 cm TL for males; and L0 = 70.8 cm TL, k = 0.02 yr−1 and L∞ = 497.9 cm TL for females. The biologically implausible L∞ occurred for females as their growth did not asymptote; a typical trait of large shark species. The maximum age estimated from vertebral analysis was 18 yr for both sexes, while the calculated longevity from the VBGF parameters was 27.4 yr for males and 32.2 yr for females. Males matured at 174.7 cm TL and 10.5 yr old, while females matured at 208.9 cm TL and 14.8 yr old.