東支那海および沖繩近海におけるマグロ延繩漁業に関する研究-I : 魚種の構成

概要

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Marlins and tunas immigrating in respective fishing grounds (SAISHUTO Gr., MESHIMA Gr., TURBULENT Gr. and UOTSURIJIMA Gr., AMAMIOSHIMA Gr., DAITOJIMA Gr., KUMEJIMA Gr. and MIYAKONANBU Gr. belonging to Okinawa Region) (Fig. 1), and caught by long line, were analized by the rank correlation of Spearman with the following results -: 1. Significant difference was found to exist in the species composition in the East China Sea and Okinawa Region (Fig. 2). Catch of marlins amounts to 95% of the total in the former region, and that of tunas over 60% in the latter (Fig. 3, Table 2). 2. Composition of kinds of marlin slightly varies all year round in the East China Sea. Fish composition in a ground bears a close resemblance to that of adjoining ground, but discrepancy is evident between two grounds which are rather widely spearated from each other (Fig. 4). 3. Sudden change in fish composition takes place in two periods, viz., April and October-November. Thus two types are recognized in the species composition for the whole year; the 1st type is composed of typical species, Albacore, Yellowfin tuna and Bigeye tuna, former whereas the 2nd one is comprised in Bluefin tuna, Yellowfin tuna and Striped marlin. The is easily seen from December to March, but the latter from May to July.
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