噴火湾周辺海域におけるスケトウダラの漁場学的研究-I : 索餌期

概要

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The bottom gill net fishery of the Alaska pollack has an economic significance in its spawning season in the adjacent waters of the Funka Bay, Hokkaido. Trammel nets were set at respective stations of 50, 100, 200, 300, 400, and 500m in depth for random sampling, and observations were made four times for its hydro-graphic conditions and food organisms of the fish in July-November, 1972. The shoal of Alaska pollack, Theragra chalcogramma (PALLAS), during its feed-ing season gets distributed at 300m depths with 3°-4°C of water temperature and 33.6-33.7‰ of salinity. These fish migrate toward the shore with the progress of maturation of their gonads. Their stomach contents comprised various organisms, such as euphausiids, am-phipods, crustacea, larvae of the Alaska pollack, and others. Euphausiids and larvae of the Alaska pollack appeared to be the most important food organisms. Particularly the latter were found abundantly in the stomach when they moved out of the bay. The rise and fall of the Tsugaru warm current affect their migration and selectivity of the spawning ground. Migration of the Alaska pollack, its yearly change and ecology of the fish in the spawning and feeding sea-sons are subjects for future study.