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

日本水産学会

日本水産学会誌

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.

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