Utility of Scales and Whole Otoliths for Aging Largemouth Bass in North Carolina

Fishery managers routinely collect scales from black basses (Micropterus spp.) for age determination; however, the validity of these ages is often unknown. The objectives of this study were to evaluate the accuracy and precision of scales and whole otoliths relative to sectioned otoliths for determining ages of largemouth bass (M. salmoides) in North Carolina. Scales and sagittal otoliths were collected from largemouth bass during spring and summer of 1997 from the Chowan river, Neuse River, B. E. Jordan Reservoir, W. Kerr Scott Reservoir, Hyco Reservoir, Tillery Reservoir, and Santeelah Reservoir. Sample sizes varied between 94 and 149 largemouth bass per water body and were pooled for data analysis. Reader-derived ages, mean total length at age capture (TL, mm), and between reader precision for scales and whole otoliths were compared against otolith sections. For comparative purposes in this study, ages determined from otolith sections were considered to be the correct ages. Overall, only 40% of the largemouth bass scale ages were in agreement with otolith section ages. Errors tended to result in age overestimation, although variation in scale aging errors increased markedly with TL. Scale ages were significantly different (P≤0.05) from otolith section ages at TL ≥230 mm. Overall, 91% of largemouth bass whole otolith ages were in agreement with otolith section ages. Largemouth bass >300 mm tended to have their ages underestimated when whole otoliths were used. Whole otolith ages were significantly different from otolith section ages at TL ≥357 mm. Differences in largemouth bass mean total lengths at age at capture between scales and otolith sections were found by age 2. No significant differences in largemouth bass mean lengths at age of capture were found between whole otoliths and otolith sections. Average percent error and coefficient of variation were in order of magnitude higher when largemouth bass were aged with scales compared to whole otoliths or otolith sections. Scales were ineffective in aging largemouth bass in this study, had relatively low levels of precision, and failed to provide quality management information. Whole otoliths were found to be relatively accurate and precise age predictors.

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ID
12169