Evaluation of Otoliths and Four Non-lethal Structures for Estimating Age and Population Characteristics of Three Black Bass Species

Black bass (Micropterus spp.) are the most popular freshwater sportfishes in North America and are intensively managed. Successful management of fish populations relies on dependable age data for estimation of age determined population rate functions (growth, mortality, and recruit- ment). Otoliths provide accurate age estimates compared to most other aging structures, but otolith removal requires fish to be sacrificed, leading some fisheries managers to rely on alternative, non-lethal methods for estimating ages of fish. However, non-lethal aging structures may produce biased age estimates when compared to otoliths. In this study, we evaluated age-estimate precision for largemouth bass (Micropterus salmoides), smallmouth bass (M. dolomieu), and spotted bass (M. punctulatus) using otoliths, dorsal fin spines, anal fin spines, pectoral fin rays, and scales. Further, we com- pared growth and mortality parameters derived using age estimates from each structure. For all species, between reader agreement (97.5%–98.2%) and precision (CV = 0.01%–2%) were high using otoliths but were low for the four non-lethal structures. In general, final consensus ages from dorsal fin spines, anal fin spines, and scales overestimated ages of younger fish and underestimated ages of older fish when compared to otolith consensus ages. Using final consensus ages from each aging structure resulted in significant differences in von Bertalanffy growth parameters calculated using non- lethal structures compared to otoliths. Estimated annual mortality rates varied among structures; however, we rarely observed significant differences in instantaneous mortality among structures. Based on these results, fisheries managers should only use otoliths for aging largemouth bass, smallmouth bass, and spotted bass. If for some reason this is not possible, managers should recognize that there may be management consequences due to imprecise and inaccurate age estimates.

Publication date
Starting page
Ending page