著者

大島,正満

出版者

東京動物學會

雑誌

動物学雑誌

巻号頁・発行日

vol.66, no.1, 1957-01-15

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As the results of the extensive collections made by the writer in the year 1949 and 1950, assisted by his student Mr. Sadahiko Imai, assistant professor of the Faculty of Fisheries of Kagoshima University, in order to compilate complete list of freshwater fishes inhabit in the streams of south werstern part of Kiushiu, it was affirmed that there exist two species of freshwater salmons in the head waters of main streams, treated under the same vernacular name 'Enoha''. One of which is evidently the river form of Oncorhynchus masou (Brevoort), while the other is the same of Oncorhynchus rhodurus Jordan & McGregor. Distributional area of the two is quite distinct, the former inhabiting in the headwaters of mam rivers which flow down to Pacific while the latter's habitats are limited to the upper streams of long rivers which enter into the Inland Sea. Oncorhynchus masou is the salmon of northern element, its distributional center being Hokkaido, instead of Oncorhynchus rodurus which is the form originated in Lake Biwa in the remote past. This facts show that the Pacific coasts of Kiushiu had been washed by the cold current coming down from Japan Sea in the prehistoric time, enabling southward migration of anadromous Salmonoid fishes like Oncorhynchus masou and Oncorhynchus keta as well. Occasional occurence of the former at the offshore of Kumamoto district and usual autumn run of the latter into several rivers in northern Kiushiu supports this supposition very strongly.