著者

大島 正満

出版者

日本動物学会

雑誌

動物学雑誌 (ISSN:00445118)

巻号頁・発行日

vol.66, no.1, 1957-01

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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.

著者

大島 正満

出版者

日本動物学会

雑誌

動物学雑誌 (ISSN:00445118)

巻号頁・発行日

vol.68, no.7, pp.259-262, 1959-07

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It was affirmed previously by means of continuous breeding experiments carried on by the former Director of the Fisheries Experiment Station of Gifu Prefecture(1924-1927) that the hybrid between the sea-run type of Oncorhynchus masou and river-type of Oncorhynchus rhodurus is fertile, while the back-cross between F_1 and the latter is entirely sterile instead. The most clear specific difference between the two river-types of the above mentioned Oncorhynchus are (1) the colouration of the round spots scattered above and below of the lateral line and (2) arrangement of the circuli in the somatic scales. In the artiffcially crossed hybrid black spots of Oncorhynchus masou reveals as an apparently dominant character while crimson spots of Oncorhynchus rhodurus subsides as recessive character while the concentric circular circuli of Oncorhynchus rhodurus becomes dominant to the broken external circuli of Oncorhynchus masou. Whether such cross exists in nature or not was a question among ichthyologists long time since. Quite recently, however, dubiuous specimens supposed to be the river from of Oncorhynchus masou have been obtaind in the upper stream of Tenriu River, mingling with 'Amago' the river-type of Oncorhynchus rhodurus. Specimens obtained by Mr. Takeo Iwasaki of Ina City has been forwarded very kindly for examination. The writer came to conclusion that the specimens exposed is really the hybrid between two species of Oncorhyuchus although intrudence of Oncorhynchus masou into Tenriu tributaries is not solved yet. In the present paper is given the description of naturally produced hybrid between Oncorhynchus masou and Oncorhynchus rhodunus, given the new name Oncorhynchus hybridus sp. nov. (Japanese name 'Hiraki-masu'). Appreciations are due to Mr. Takeo Iwasaki by whose efforts such interesting specimens came to the writer's hand.

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.19, no.230, pp.359-362, 1907

著者

大島 正満

出版者

日本魚類学会

雑誌

魚類学雑誌 (ISSN:00215090)

巻号頁・発行日

vol.5, no.1-2, pp.1-11, 1956-01-30 (Released:2011-02-23)

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Kuma River of the Kumamoto Prefecture is famous in producing “ayu, ” Plecoglossus altivelis, of good quality, due to the suitable environmental conditions. Quite recently, however, utilization of the stream for the sake of generation of electricity necessitated to erect the darn of 34 meter high at the down stream in order to construct water reservoir. The Prefectural Government started the works last year and the dam. which is not provided any fish ways has been completed on 10 th of December, 1954, shutting up completely the passway of the anadromous fishes especially.Consequently, complains of fishermen and inhabitants of the upper streams opposing to the policy of the Government paying no attention for fish culture, especially to keep good name of Kuma River in “ayu” fishing, became furious. In order to solve this hard problems, viz, electricity nor fishing industry, authorities of the Government promissed to liberate large number of “ayu” fry in the upper streams per year, to meet the both ends.This attempts has been fulfilled for the first time in the spring ot the present year since, fries of sea-run form caught at the estuary of Kuma River and other parts in Kiushu as well as dwarf land-locked form of the Lake Biwa and Ikeda being libertated in the main and branch streams of Kuma River.In the present paper are shown morphological differences between sea-run form of “ayu, ” grown at the both sides of the dam; effect of suitable baits upon development of land-locked dwarf form of “ayu” originated in the Lake Ikeda ; distinction between sea-run form and land-locked form of “ayu” after fattening, from the stand-point of scale figurations, etc.