Age Estimation and Length Back-calculation for Known-age Largemouth Bass

Scales and otoliths from largemouth bass (Micropterus salmoides) of known ages (age 6, 7, and 8) were prepared and examined by 3 experienced readers who were uninformed of specimen age or length. Results indicated limited agreement between readers and numerous inaccurate age estimations. Among 97 scale samples read, all 3 readers only agreed on the age of a single specimen which was older than estimated; using otoliths, readers agreed on 4 specimens which were correctly aged. Percentage of correctly-aged fish ranged from 10% to 30% with scales and 39% to 47% with otoliths. Percent of fish correctly aged ± 1 year ranged from 29% to 77% with scales and 78% to 98% with otoliths. Backcalculated lengths-at-age based on scale annulus measurements made by a fourth reader who knew specimen age, length, and sex were typically less than actual measurements taken each year (in October) with the greatest differences for earlier years of life. Therefore, accurately aged scales provided back-calculated lengths as expected for criteria in this study. Similar back-calculations based on otolith annuli yielded inconsistent results without obviously greater deviations from known length in younger fish and lesser deviations in older fish.

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