Method, Validity, and Variability in the Age Determination of Yellowtail Rockfish (Sebastes flavidus), Using Otoliths

Abstract

A method using otoliths is presented for the age determination of yellowtail rockfish (Sebastes flavidus). Most of the details of this method are applicable to other species of rockfish. The method is validated in younger fish by documenting growth of the otolith annular zone by month, and by comparison with ages read from scales. Further validation is provided by length-at-age data, which show monotone growth for both males and females. Age reader variability was analyzed for each age category using random effects analysis of variance. This analysis showed that within-reader variances were similar for the two readers. Although there were significant variance components due to between-reader differences for aging some age categories, the contribution of this variance component to total variability was negligible. The standard deviation for an age determination of an otolith was similar for both readers, ranging from about 0.6 at 8 yr to about 1.6 at 19 yr. For both readers, the coefficient of variation was approximately 0.08 at all ages. Key words: Sebastes flavidus, age determination, otoliths