Abstract
My observations on 64 males (54-64cm long) and 61 females (52-65cm long) of O. keta as well as 69 males (54-64cm long) and 84 females (50-62cm long) of O. nerka caught in Kamchatski Gulf during a period from May 26th to June 17th, 1940 confirmed that the former is distinguishable from any other species of the genus Oncorhynchus in having 13-17 silvery caudal rays besides ordinary ones (Fig. 2, B). The silvery lustre is preserved for a long duration of time in salted or smoked condition whereas it does not last more than three weeks when fixed in formalin, a fact that accounts for the total absence of such a feature put on record. The depth (vertical diameter or median width, Fig. 1, A) and thickness (side diameter or sagittal width Fig. 1, B) of the caudal peduncle are variable, but the depth proved smaller in O. keta than in O. nerka and the ratio of depth to thickness was also found smaller in the former than in the latter when statistically examined (Tables 1-3, Fig. 3).
