噴火湾周辺海域におけるスケトウダラ成魚群の生活期別生態について
The authors examined the biological data of adult Alaska pollack Theragra chalcogramma (PALLAS) caught by bottom gill net at three definite stations (100m, 200m and 300-350m depth) in the adjacent waters of Funka Bay from February 1974 to February 1975. 1. In the spawning period, gonads of males rip...
| Published in: | NIPPON SUISAN GAKKAISHI |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | Japanese |
| Published: |
日本水産学会
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| Subjects: | |
| Online Access: | http://hdl.handle.net/2115/38657 https://doi.org/10.2331/suisan.49.577 |
| Summary: | The authors examined the biological data of adult Alaska pollack Theragra chalcogramma (PALLAS) caught by bottom gill net at three definite stations (100m, 200m and 300-350m depth) in the adjacent waters of Funka Bay from February 1974 to February 1975. 1. In the spawning period, gonads of males ripen earlier than females and males migrate from the feeding grounds (300-350m depth) to the spawning grounds (near 100m depth) before females. Most of the males remain in the spawning grounds through the period, while females migrate to the spawning grounds in the order in which gonads ripen and leave soon after spawning. Consequently, males abound remarkably in the spawning grounds. There is no feeding activity among the spawners. 2. In the transitional period from the end of spawning period to the beginning of feeding period, almost all the fish disperse chiefly to the offshore area in search of their food organisms. 3. In the feeding period, adult fishes concentrate in the bottom layer water of the Oyashio current (300-350m depth) which is abundant in Euphausiids and Amphipods. But, in 1974 when these food organisms were scarce fishes migrated to area near 200m depth and fed chiefly on the young Alaska pollack and shrimp. 4. In the transitional period from the end of feeding period to the beginning of spawning period, adult fishes mature rapidly. Males begin to migrate to the spawning grounds and females continue light feeding activity in the feeding grounds. 噴火湾周辺海域において1974年2月から1975年2月にかけて毎月1回底刺網を用いてスケトウダラを漁獲し，その標本の生物学的資料に基づいて成魚群の生活期を4期に区分して月別，地点別に検討し，各生活期における生態について考察した。1. 産卵期（12-3月）には雄が雌より生殖巣の成熟が早く，雌に先行して産卵場になる水深100m付近の浅海域に集中する。雌は沖合の水深300-350m付近に多いが，生殖巣の成熟したものから順次産卵場に回遊し，産卵を終えると沖合に去る。したがって産卵場の群は雄の割合が多く，ほとんど摂餌することなく産卵活動をしている。2. 産卵期から索餌期への移行期（3月末-4月末）の魚群は一部産卵しているものもあるが，ほとんどのものは産卵を終え，産卵活動によって消耗したエネルギー補充のため，餌を求めて主に沖合へと広範囲に分散する。3. 索餌期（5-10月）には浅海域が津軽暖流系水の流入と夏期の昇温および餌料プランクトンの減少のため，寒冷で餌料プランクトン豊度が高い水深300-350mの親潮系中層水域を餌場として集群する。しかし餌料プランクトン豊度が低い年には噴火湾内から沖合の底層に回避し始めるスケトウダラ幼魚群やホッコクアカエビを捕食対象として水深200m以浅域にまで餌場を拡大する。4. ... |
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