Nebraska Cooperative Fish & Wildlife Research Unit
Date of this Version
2012
Citation
North American Journal of Fisheries Management 32:1175–1179, 2012; DOI: 10.1080/02755947.2012.717523
Abstract
Scales are perceived to give reliable estimates of age of fish in northern latitudes and unreliable estimates of age in southern latitudes, whereas otoliths are perceived to give reliable estimates of age regardless of latitude. The objective of our study was to assess the influence of latitude on the estimates of ages derived from scales and otoliths for bluegill Lepomis macrochirus. Our hypothesis was that a south-to-north gradient exists for precision between scales and otoliths with partial agreement between age estimates derived from scales and otoliths for fish in southern latitudes and nearly complete agreement between age estimates derived from scales and otoliths for fish in northern latitudes. Fish were sampled from Louisiana (latitude = 30º43'48''N) to North Dakota (latitude = 47º05'49''N). Contrary to a priori expectations, we did not find greater agreement in age estimates between structures in northern bluegill stocks than in those in the southern USA. The low agreement between structures increases uncertainty in the source of aging error, given that both scales and otoliths are valid structures (i.e., age estimates validated as accurate) for estimating ages of bluegills. Biologists should not compare age-dependent parameters for bluegill populations derived from different aging structures.