The Opercular Bone of the Yellow Perch, Perca flavescens, As a Tool for Age and Growth Studies

Abstract

IT is agreed upon by fishery biologists that scales are a most useful and often the most satisfactory tool in the assessment of fish age and growth. Yet, other bony parts of fishes are known to bear year marks, and when scales are absent or for other reasons are not satisfactory for reading the age of fish, otoliths, vertebrae, dorsal spines, opercular bones, and other structures can be employed for the purpose. In a study aimed at following the size increase of yellow perch in Lake Mendota, Wisconsin (Bardach, 1951), a secondary objective was to determine whether the opercular bone could be used in this species for calculating the sizes of fish at previous ages of their lives. These structures have been shown to bear yearly marks in Perca fluviatilis Linnaeus, the closely related European species; in fact, the opercle was found to be extremely well suited for growth analysis as an alternative or even in lieu of scales (Roper, 1936; Svetovidov, 1929; LeCren, 1947).