近年のスケトウダラ太平洋個体群年級群強度と摂餌開始期の海洋環境

概要

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To understand the survival in the first-feeding stage of walleye pollock, Theragra chalcogramma, of the Pacific population in strong year classes(1991, 1994, 1995 and 2000), hydrographic and food conditions in winter in Funka Bay (nursery ground for pollock larvae) were investigated from 1991 to 2003. A delete intrusion of the Oyashio coastal cold water were observed and relatively warm temperature conditions were measured in the inner area of Funka Bay in 1991, 1994, 1995 and 2000. Relatively high densities of copepod nauplii, which were main food for first-feeding larvae, were also observed. These results indicate that warm water temperature sustains high reproduction of Oithona similis that are main producer of copepod nauplii in winter in Funka Bay, and a high feeding activity of first-feeding pollock larvae. Therefore, it can be concluded that suitable oceanographic conditions for survival of first-feeding pollock larvae of the Pacific population were occurred in Funka Bay in 1991, 1994, 1995 and 2000.
2008-05-30