Life history of the blackspotted whipray Himantura astra
Features of the life history of Himantura astra from north-east Australia were examined including its age and growth, reproduction and diet. Centrum edge and marginal increment ratio analyses were used to validate annual band formations with the Gompertz growth function providing the best fit to male (WD∞ = 722·7 mm, k = 0·104) and female (WD∞ = 821·8 mm, k = 0·073) disc width (WD)-at-age data. At 29 years, the maximum age of females was higher than males (18 years). Sizes at 50% sexual maturity (WD50) for males and females were 469·3 and 462·3 mm, respectively. Ages at sexual maturity (AM50) were reported at 7·32 (males) and 8·67 (females) years. An index of relative importance (IRI) revealed carid shrimps (77·9%), brachyurans (12·1%) and stomatopods (4·9%) as the most important prey groups, with prey diversity increasing with WD from 0·92 to 1·63 (Shannon–Weiner index). This study provides significant insights into the biology of H. astra and contributes to the ongoing development of fisheries-based risk assessments for this species.