Predicting Sablefish Age Using Otolith Characteristics

摘要

Validation studies have shown that sablefish (Anoplopoma fimbria) otoliths contain several false annuli along with the true annual marks. Distinguishing between the two is difficult and agreement among readers is much lower for sablefish than for most other species. Because of the low precision, the authors used linear and nonlinear regression analysis to develop models for predicting fish age from otolith characteristics (weight, length, thickness, and width) and fork length. Correlation analysis indicated a strong relationship between several otolith characteristics and fish age, with highest correlations observed for otolith thickness. Multiple regression models based on otolith characteristics accounted for a relatively high fraction (75%) of the variability in age. However, agreement between model-predicted age and age determined by readers was much lower than agreement between the two readers. Because information on age composition is used in managing the sablefish fishery, the subjectivity associated with ageing could undermine the reliability of management decisions. For that reason, it would be preferable if reliable objective methods for determining sablefish ages could be developed.