Comparison of Scales, Pectoral Fin Rays and Opercles for Age Estimation of Ontario Redhorse, <em>Moxostoma</em>, Species

Opercle based age estimates of four redhorse species ( Moxostoma anisurum , M. carinatum , M. macrolepidotum and M. valenciennesi ) were compared with those from two structures that can be obtained non-lethally (scales and pectoral fin rays). For all species, age estimates from scales were significantly lower than those obtained from fin rays and opercles. After ages 4 to 5, age estimates from scales were consistently lower than those from the opercle. Overall differences between age estimates from fin rays and opercles were only detected for M. anisurum . For all species, age estimates from fin rays were consistently lower than opercles after ages 12 to 15. Closer agreement among different structures was identified for populations of M. macrolepidotum comprised of younger individuals. Maximum ages reported for Ontario populations were higher than those previously reported across the species’ ranges, reflecting either geographic differences in growth and longevity, or the historical use of scales for age estimation.