| Summary: | The distribution pattern of demersal fish and food habits of the dominant fish species were studied off the Pacific coast of eastern Hokkaido during the summer of 2003-2004 and the winter of 2005. In summer, the assemblages on the upper continental slope (<400m) were primarily dominated by single species such as walleye pollock Theragra chalcogramma. The assemblages on the upper-middle slope (400-700m) were dominated by threadfin hakeling Laemonema longipes, longnose eel Synaphobranchus kaupii, and soft eelpout Bothrocara molle. The assemblage on the lower-middle slope (>700m) was dominated by macrourids(chiefly, Coryphaenoides cinereus and C.pectoralis). However, in winter, the boundary between assemblages on the middle slope was obscured slightly by the bathymetric descent of threadfin hakeling from the upper-middle slopes to the lower-middle slopes. Most dominant fish species preyed primarily on nekton, micronekton and zooplankton. However, the dominant fish species utilizing common food organisms belonged to different assemblages. This pattern of assemblage structure is characteristic of weak inter-specific competition for food and appears to be an important factor underlying increased biomass of demersal fish.
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