Temporal and spatial characteristics of warm and cold eddies in the Kuroshio-Oyashio transision regions, and their effects on larval survival.

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In the first year, statistical analysis of the past oceanographic data was proceeded. Obtained result are as follows, (1) Kuroshio water spreads toward Kuroshio-Oyashio transition region, whose behavior is described by an isotherm defined at the northern edge of the trough of the meandered path the Kuroshio Extension, (2) the predominant periods of the north-south fluctuation of the northern boundary of the Kuroshio Extension are 20-30 days and about 50 days, which correspond to the perio of the frontal waves of the Kuroshio in the south of Japan. Though the first and second years, field observations were persecuted by using R/Vs Hakuho-Maru and Tansei-Maru as well as a car ferry boa which is shutting between Tokyo and Tomakomai. Obtained results are as follows, (3) the cross sections of the current velocities near the ridge of the meandered path observed with CTD and ADCP shows peaks in the both sides of the axis, (4) origin of the spread Kuroshio water comes from the dept of 300-400m in the Kuroshio axis along the isopicnal surface, (5)drifting buoys near the Kuroshio front detrained from the Kuroshio in the down stream side of the ridge of the meandered Kuroshio path when the anticyclonic dcurvature increases, (6) local characteristics and their reasons of the spring bloom off the east coast of Japanese main island were made clear based on the continuous water sampling from the bottom of the ferry boat during February-June, 1997.