オホーツク海北部における夏季のニシンの研究. II, 魚群組成の特徴，および魚群の分布と海況との関係について

• Published in: NIPPON SUISAN GAKKAISHI
• Main Author: 高橋, 豊美
• Format: Article in Journal/Newspaper
• Language: Japanese
• Published: 日本水産学会
• Subjects: 664; Okhotsk; Oyashio; The Shoals; okhotsk sea
• Online Access: http://hdl.handle.net/2115/38566; https://doi.org/10.2331/suisan.42.427

In a previous paper, the size and age composition of the shoals and several biological characteristics of the herring, Clupea pallasi, in the northern part of the Okhotsk Sea in the summer of 1971 were reported. In the present study, the author attempted to clarify the features of the age composition of the shoals and the relationship between their distribution and hydrographic conditions on the surface layer. Fish samples and data of oceanographic observation were obtained by the research vessel "Oyashio Maru" in the northern part of the Okhotsk Sea in the summers of 1971-1973. The surface gill nets used were composed of nets of various mesh sizes 30, 35, 42, 48, 55, 63, 72, 82mm, and others, and the results of the analysis of these mesh selection curves suggested that these nets can relatively capture herrings non-selectively. The results obtained are summarized as follows: 1) The shoals were separated into 3 groups according to the type of their age composition; Shoal A was composed of fish older than 4 years old (3+), Shoal B was mainly composed of 2-3 year-old fish, and Shoal C was mainly composed of 4 year-old fish. 2) Shoal B was distributed in comparative warm waters (12-14℃), where the temperature and salinity gradient were small. 3) Shoal C was observed in only remarkably low salinity areas (27.1-31.2‰), where the discharges of rivers could have some influence. 4) There is a possibility that the extension of the low salinity waters helped to define the distribution of Shoal A. 5) It is deduced that each shoal generally separates from one another geographically due to the distribution of Shoal B and Shoal C in connection with peculiar water masses, respectively. 1971～1973年の8～9月にオホーツク海北部で行なわれたさけ・ます幼魚採集用の表層流網に混獲されたニシンの標本，および海洋観測結果に基づき，当海域における夏季ニシンの群組成の特徴，および魚群の分布と海況との関係について検討した。１） 夏季のニシン群は年令構成の特徴からみて，4才以上の年令魚で構成されている中・高令魚群，2～3才の若令魚主体群，および4才魚主体群の以上，3つの魚群集団に分けられる。これらの各群は一般に地理的な分離を示す。2) 若令魚主体群は表層が温暖（12～14℃）で，水温・塩分の傾度が小さい安定した海洋環境の中に分布する。3) ...