Estimates of age and growth of ocean perch, Helicolenus percoides Richardson, in south-eastern Australian waters

Abstract

Methods of age determination, age and the parameters of the von Bertalanffy growth function are described for ocean perch, Helicolenus percoides Richardson, from the continental slope in eastern Bass Strait. Comparison of scales and otoliths revealed the latter to be superior for age estimation. Annuli were used for age determination; 97% of whole otoliths with 2-15 annuli were readable, compared with only 37% of older (15 + annuli) otoliths. Of sectioned otoliths with 15 + annuli, 81% were readable and the oldest age estimated was 42 ( ±3) years, compared with only c. 30 years from whole otoliths. For whole otoliths, the precision of intra-reader and inter-reader age estimates was, respectively, 89% and 79% within ±1 annulus, and the average error was 4.6% and 5.0%. For sectioned otoliths, intra- and inter-reader precision was, respectively, 60% and 53% within k 1 annulus and the average error was 3.9% and 5.4%. Comparison of age estimates from whole otoliths and sectioned otoliths gave a precision of 84% within ±1 annulus and average error of 2.8%. Precision of age determination decreased with increasing age for both methods. Age validation, using Petersen's length-frequency method and a marginal-increment method, was unsuccessful. Mean length-at-age and the values for the parameters of the von Bertalanffy growth function were estimated. For female and immature fish: K = 0.107 and L_∞ = 44.68 fork length (cm), and for male and immature fish: K = 0.115 and L_∞ = 43.19 fork length (cm). The growth of males and females was statistically different.