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母船式鮪漁業の漁況に関する研究―VII 西南太平洋における鮪類の体長組成について(1959年8月~11月)

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Title: 母船式鮪漁業の漁況に関する研究―VII 西南太平洋における鮪類の体長組成について(1959年8月~11月)
Other Titles: Studies on the Fluctuation in Catch of the Tuna-fshing Fleet―VII Length Frequency of Tunas Caught from the Western South Pacific Ocean during four Months from August to November 1959
Authors: 古賀, 重行
Authors (alternative): Koga, Sigeyuki
Issue Date: 31-Aug-1961
Publisher: 長崎大学水産学部
Citation: 長崎大学水産学部研究報告, v.11, pp.89-95; 1961
Abstract: Basing on the data gathered by Koyo tuna-fishing fleet in the Fiji area during four months from August to November 1959, the following characters are shown in regard to the size composition in the Western South Pacific Ocean. 1 Yellowfin tuna In the Fiji area, according to proceed on southward, larger fishes-more than 100cm in length-are increased and the small fishes-less than 100cm in length-are decreased. But, in the bigeye tuna, this phenomenon is quite contrary. The modal size of the principal catch become smaller year after year, in regard to the hooked-rate, it decreased gradually from season after season. Therefore, these phenomena are supposed to be within the bounds of possibility that it is caused by the influence of the intense fishing effort. In the South Equatorial Pacific Ocean, the size of fishes are larger to the eastward. But in the south of 20°S, fish to east will be smaller just opposite. Size compositions differed by season and area, but the former difference are not distinct. 2 Southern bluefin tuna In the sex-ratio, the size of male is bigger than that of female. It is recognized clearly that there is a remarkable difference of size composition by area. The catcher of the southern bluefin tuna are consist of larger size in the north of 27°S and between 95°E-125°E, in the south of 30°S and between 170°E-170°W, however, the fish group are composed of middle size. / 第19次広洋鮪船団操業を通じて,南太平洋におけるマグロ類の体長組成を検討した結果,次のような傾向が認められた. 1. フィジー海域にみられる現象 (1) キハダマグロ ① 南緯する程大きい型の体長群が増加して小さい型の体長群減少の傾向がうかがわれる.② 季節の移行に伴って次第に魚体は小型化している.且,釣獲率もそれに従つて減少傾向を示している.従ってこの現象は当フィジー海域に加えられた漁獲強度の増大によって,130cm以上の大型群減少の傾向を招来したことに起因するものと思われる.(2) メバチマグロ ① 南緯する程大きい型の体長群が減少してキハダと逆の傾向を示している. ② 季節の移行に伴って魚体はキハダと同様,小型化しているように考えられる. (3) 濠洲鮪 性による魚体差が明瞭にうかがわれ,雄は雌より大きい傾向を示した. 2 南太平洋赤道海域にみられる現象 (1) キハダマグロ 東方へ移行する程大型のものの割合が増加する傾向を認めた.20°S以南の東経海区は赤道海域と逆の地域的変化を認めた. 体長組成の季節変化は地域的な差異に比して著しく小さいように思われる. (2) 濠洲鮪 顕著な地域的魚体の差が認められる.
URI: http://hdl.handle.net/10069/31691
ISSN: 05471427
Type: Departmental Bulletin Paper
Text Version: publisher
Appears in Collections:第11号

Citable URI : http://hdl.handle.net/10069/31691

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