Age, growth and maturity of the Australian blackspot shark (Carcharhinus coatesi) in the Gulf of Papua

Abstract

Small-bodied coastal sharks are often caught as by-catch in fishing operations. Life-history information for these sharks is needed to ascertain the level at which these populations are potentially affected by fishing. This study determined the age, growth and maturity of Carcharhinus coatesi captured by prawn trawlers in the Gulf of Papua. Using vertebral aging and an information-theoretic multimodel approach, the von Bertalanffy growth model fit the data best; parameters were L0=40.6cm±0.8, L∞=74.8cm±2.1, k=0.33year−1±0.06. Length-at-maturity analysis indicated that males reach maturity at L50=66.3cm (CI: 63.8, 71.4) and L95=71.6 (CI: 64.6, 74.2) cm while females matured at L50=71.4cm (CI: 61.5, 72.01) and L95=72.5cm (CI: 62.7, 74.0). Age-at-maturity estimates showed that both males (A50=5.1 years (CI: 4.6, 7.1), A95=6.4 years (CI: 5.1, 7.2)) and females (A50=5.3 years (CI: 3.5, 8.7), A95=7.4 years (CI: 3.6, 8.8)) reach maturity at about the same age. This study addresses the need for specific life-history information for a data-deficient species in a region that has remained relatively under-researched but in need of ongoing improvements to fisheries management.