Age and growth of blue grenadier, Macruronus novaezelandiae (Hector), in south-eastern Australian waters

Abstract

Blue grenadier, Macruronus novaezelandiae, from south-eastern Australian waters were aged, using their otoliths (whole and in transverse thin sections). The greatest recorded age was 25 years. A double blind test showed that the recorded ages were sufficiently reproducible to use in fitting growth curves (Index of Average Percent Error: 8%), but not sufficiently so to assign individuals to particular year-classes. Von Bertalanffy growth curves were fitted to both length and weight data. For males, L_t = 90.7 (1 - exp[-0.256(t + 1.21)]} and W_t = 2.62 (1 - exp[-0.277(t + 1.39)]}³. For females, Lt = 99.3 {l - exp[-0.203(t + 1.48)]} and Wt = 4.16{1 - exp[-0.157(t + 2.93)]}³. L is the length in centimetres, W is the weight in kilograms and t is the age in years. A comparison with length-frequency modes validated the growth curves for immature fish, but no validation was possible for the adults. The $exes have qignificantly different growth patterns. Their growth parameters are typical of those of commercially exploited, temperate gadoid fishes and show no modification for the deep-water zone inhabited by blue grenadier.