Age, growth estimates for pink ling, Genypterus blacodes (Schneider), and gemfish, Rexea solandri (Cuvier), from Eastern Bass Strait, Australia

Abstract

Age and growth were estimated from counts of otolith annuli for pink ling (Genypterus blacodes) and gemfish (Rexea solandri). Sections of otoliths were preferable for age determinations of pink ling, whereas whole otoliths were preferable for gemfish. Validation of the assigned age classes was not achieved. Petersen's length-frequency method was unsuccessful and marginal increment methods were unsuitable for the species studied. Growth of males and females did not differ significantly for either pink ling or gemfish. Both species had a relatively slow growth rate, had a moderately long life-span and could reach body lengths in excess of 1 m. Maximum ages of pink ling and gemfish were, respectively, 21 and 13 years. Mean length-at-age and the von Bertalanffy growth functions were estimated. For pink ling (all individuals combined), K = 0.095 and L_∞ = 135.5 cm. For gemfish the best estimates were K = 0.153 and L_∞ = 112.3 cm. Precision of age determinations made independently by two readers for pink ling and gemfish, respectively, was 65% and 95% within ±1 annulus; average per cent error, respectively, was 4.7% and 3.1%. Paired t-tests on ages assigned to each species by the two readers indicated no significant difference between ages assigned to gemfish, but there was a significant, albeit unbiased, difference for ages assigned to pink ling. However, for pink ling, estimates of the growth parameters derived separately from age determinations by the two readers were virtually identical.