Comparison of Aging Methods and Validation of Otolith Ages for the Rainbow Darter, Etheostoma caeruleum

Abstract

Etheostoma caeruleum were sampled from the James River, southwest Missouri, during eight months, July 1996 through May 1997. Ages were estimated from whole and sectioned otoliths (sagittae) and from scales by counting annuli. Edge analysis indicated that otolith annuli (opaque zones), visible in whole and cross-sectioned otoliths, formed yearly, primarily during July through September. In contrast, scale edge analysis indicated no clear pattern of annulus formation. Independent readers agreed on 63–73% of ages using otoliths but only 38% of ages using scales. Sectioned and whole otolith age estimates made by one experienced reader agreed for 68% of individuals. Scales underestimated age compared to otoliths, and maximum otolith age was five years.