ベーリング海におけるアラスカメヌケの鱗相-I

Abstract

The scale characters of Pacific Ocean Perch, Sebastodes alutus, and its variations by body regions were investigated for two specimens caught in the Bering Sea in 1965 (Table 1 and Fig. 1). The scale is of a ctenoid type by many characters recognized on the surface of scale (Fig. 2). There are many ridges concentrically around the central plate on the covered portion. The widely spaced ridge zone and the close one appear alternately, and they are considered to be the growth zone and the resting zone respectively (Figs. 2 and 3). The radius of the resting zone, measured from the converged point of grooves to the each outer edge, shows a smooth curve (Fig. 4), but the cumulative number of ridges indicates a inflective line (Fig. 7). The resting zones are supposed to be formed periodically from the Walford's graphic method for their radii (Fig. 6). These characters aforementioned were observed similarly on every scale of the same fish irrespectively of samlping region, and of the shape and the size of scale (Fig. 4, 5, 6 and 7). Therefore, there is a good possibility for determining the age of S. alutus by the scale character, and so far as age determination is concerned, there is no need of strictly defining of scale sampling region.