噴火湾周辺海域におけるスケトウダラの漁場学的研究. III, 海況の季節変化

• Published in: NIPPON SUISAN GAKKAISHI
• Main Authors: 前田, 辰昭, 高橋, 豊美, 上野, 元一
• Format: Article in Journal/Newspaper
• Language: Japanese
• Published: 日本水産学会
• Subjects: 664; Oyashio; Theragra chalcogramma; Alaska
• Online Access: http://hdl.handle.net/2115/38570; https://doi.org/10.2331/suisan.45.1137

In the previous papers, the distribution and migration in feeding and spawning seasons of adult Alaska pollack, Theragra chalcogramma (PALLAS), in the adjacent waters of the Funka Bay, Hokkaido were examined. However, the relationship between the habits of adult Alaska pollack and environmental conditions throughout the year is not clear. For this reason, the authors investigated water temperature, salinity, food organisms and biological factors of fish once a month from February 1974 to February 1975 six definite stations. This paper deals with the examination of the seasonal variations of water mass in this area. 1. The Tsugaru warm current (salinity more than 33.8‰ as an indicater of presence) enters this area through the mid-water layer in June and occupies the widest sphere in November. In December the current falls off and disappears in January. 2. The surface layer water of the Oyashio current (salinity less than 33.2‰) occupies most of the surface and mid-water layers in February and gradually declines from March. In June this water is thrust toward the coastal area by the inflow of the Tsugaru warm current and almost disappears in November. 3. The bottom layer water of the Oyashio current (temperature less than 3.5℃ and salinity less than 33.7‰) occupies about 200-450m in depth near the bottom in February, but the range gradually decreases with the inflow of the Tsugaru warm current and shows the minimum range during December and January. 著者らは前報で噴火湾周辺海域におけるスケトウダラ成魚群の索餌期と産卵期の生態について報告した。本報では年間を通した魚群環境を明らかにするために，6定点で1974年2月から1975年2月にかけて毎月1回水温と塩分を調査した結果から，水塊の季節変化を検討した。1. 津軽暖流系水は6月に沖合の中層から増勢し始め，11月には最も広範囲を占めるようになる。しかし12月には劣勢に転じ，1-2月には消滅する。2. 親潮系表層水は2月に最も分布域が広いが，3月以降は次第に衰退し，6月以降の津軽暖流系水の流入期には沿岸に押しやられ，11月には完全に消滅する。3. 親潮系底層水は親潮系表層水とその起源を共にすることから，盛衰の季節変化がほぼ一致し，2月に最も強く，12-1月に最も弱く分布域も小さい。