Age estimation and maturity of the ridge-scaled macrourid (Macrourus whitsoni) from the Ross Sea
Juveniles of the macrourid Macrourus whitsoni were collected by the NIWA research vessel Tangaroa during the BioRoss survey of the western Ross Sea and Balleny Islands in 2004. Intensive analysis of otoliths from these specimens greatly increased confidence in the interpretation of otolith growth zone structure, supporting the otolith interpretation protocol used in previous work on this species. Von Bertalanffy growth models assuming different growth by sex and by year-within-sex were fitted separately to a revised length-at-age dataset and compared using the likelihood-ratio test. Von Bertalanffy parameters for the pooled dataset with unsexed juveniles are L∞ 76.12, K 0.065 and t0 –0.159 for males and L∞ 92.03, K 0.055 and t0 0.159 for females. Revised estimates of the mean total length-at-maturity (38.8 and 46.4 cm) and mean age-at-maturity (10.6 and 13.6 years) are presented for males and females respectively, using a reduced probit model.