The age determination of fish species is fundamental to the assessment and management of fisheries worldwide (Morison et al., 1998a). The accuracy of assessments is highly dependent on age estimates, so it is vital that age estimates provided are as accurate as possible. Most fish ages are determined using otoliths (ear-stones) found in the sacculus of the inner ear. Otoliths grow continuously throughout the life of a fish and the formation of annual growth zones provides a mechanism to allow individual fish age to be determined (Pannella, 1971). The annual zones (annuli) are laid down incrementally over days, months or years, and counts of annuli provide estimates of fish age.