Precision Analysis of Three Aging Structures for Amphidromous Dolly Varden from Alaskan Arctic Rivers

Author： Stolarski Jason T. Sutton Trent M.

ISSN： 0275-5947

Source： North American Journal of Fisheries Management, Vol.33, Iss.4, 2013-08, pp. : 732-740

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

The 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 malma have 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 otoliths beginning 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