北海道東部オホ-ツク海における早期来遊シロザケの遊泳行動〔英文〕

概要

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This paper deals with the swimming behavior of chum salmon Oncorhynchus keta, the sea condition of swimming azea of the test fish in the '85 experiment, and summary of the experiments conducted in and after '82 in eariy migratory season at Okhotsk sea off the coast of Shiretoko peninsula and its neighborhood, Hokkaido. On the swimming behavior of the test fish in '85 experiment, swimming direction showed a notable eastward element, and mean horizontal swimming speed was faster than Ichihara's es-timated value (1.0 FL/s), the trend of vertical movement showed that the test fish swam com-paratively deep before and after noon, just below the sea surface without vertical movement at mid-night, with notable vertical movement at sunrise. The sea condition of the '85 experiment can be considered as normal condition by oceano-graphic observation at the experiment. As the results of the experiment, conducted in and after '82, the migration of chum salmon was assumed to be as follows, chum salmon migrated to Kitamiyamato bank along the East Sahalin Currents, and diverged to east and west at an area from Kitamiyamato bank to Cape Notoro or off shore Monbetsu. On swimming depth, it was recognized that maximised depth is not always shown in a sea area with enough depth and the test fish swam at comparatively shallower layer in deep sea, bottom layer in shallow sea.