The ayu Plecoglossus altivelis of the Japan and Ryukyu Islands were recently found to differ considerably in both morphological and biochemical-genetic characters, and, within the Japan lslands region, a landlocked population of Lake Biwa to bear traits somewhat different from those of other amphidromous populations.1,2) Azuma3) showed a large difference in the number of longitudinal scales in two samples of Lake Biwa and amghidromous populations, but so far, this particular aspect has not been

more »

... investigated in much detail. In the present study, investigation was made of geogaphic variation in this number using the same samples from various localities in the Japan and Ryukyu Islands as those in the previous study.2) The following 7 population samples were examined (the sample codes were the same as in the previous study2)): 3) Yoshida River, Miyagi Pref., 43 inds.