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AbstractThe accuracy of population statistics and the validity of management actions they motivate are in part dependent on the acquisition of quality age determinations. Such data for northern-form Dolly Varden Salvelinus malmahave been traditionally garnered using otoliths, despite little research investigating the consistency of this or alternative nonlethal techniques. To address these gaps, the precision of age determinations generated from scales, otoliths, and fin rays was examined for 126 amphidromous Dolly Varden collected from two Arctic rivers. Three independent readers, age-bias plots, coefficients of variation (CVs), and percent agreement (PA) were used to estimate bias and precision for among-reader, within-structure comparisons and within-reader, among-structure comparisons. Among-reader, within-structure tests of CVs suggested that otoliths produced more precise age determinations than fin rays. Furthermore, the CV for scales was intermediate to and not significantly different from those for otoliths and fin rays. Age-bias plots suggested that, scales consistently underestimated age relative to otolithsbeginning at age 6. Underestimation was also apparent, but less distinct, within fin ray–otolith and scale–fin ray comparisons. Potential sources of error and management implications are discussed. Because scale and otolith ages exhibited little bias within cohorts younger than age 6, age may be determined nonlethally in these cohorts using scales; otoliths should be used otherwise.Received April 27, 2012; accepted May 13, 2013 |
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