Age determination of chum salmon using scales becomes difficult as sexual maturation progresses. We examined and compared the working efficiency and accuracy of aging methods using scales, otolith surface, and otolith section with chum salmon. The percentage of age estimated correctly, cross-checked with known age by the otolith thermal mark and release protocol, was under 80 for the otolith surface and the common otolith sectioning methods in which otoliths are sliced to around 150 mm thickness. The accuracies were 100 using scales and thinner otolith sections of around 80 mm thickness. We therefore recommend employing the more accurate aging methods using scales and thinner otolith sections in line with the working efficiency and maturational conditions.
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