Elucidation of the relationship between migration pattern and sea environment, and prediction method of relative abundance for yellowtail [Seriola quinquenradiata] in the Japanese waters

1-(1)-1) Experiment of release and recapture using archival tag revealed that the area of migration of 0 and 1 year old yellowtail in the Sea of Japan is restricted small scale. 0 and 1 year old fish in western waters thean Noto Peninsula stayed near release points all of the year. 0 and 1 year old fish in northern waters than Nato Peninsula, northern area of the Sea of Japan stayed among Noto Peninsula (Wajima) and off Aomori Prefecture. They did not move to west of Noto Peninsula even in winter, differ from in 1980s when ocean regime was cold.1-(1)-2) Young yellowtail occurred in northern waters than Noto Peninsula even when the water temperature showed the minimum (March and April). The ambient water temperature exceed 10degC at that time according to the analysis of water temperature record obtained from archival tag record. So, it is supposed that young yellowtail can pass winter where waters exceed 10degC in Japan Sea. It is also supposed that yearly change of water temperature in winter (when water temperature is the minimum, i.e. March and April) may cause the change of migration pattern of young yellowtail in this area.1-(2) It is estimated by synthesis of the past and present study that young yellowtail (0 to 2 years old) in the Sea of Japan form small scale migration group and the group west of Noto Peninsula and that northern part of Noto Peninsula do not exchange until their maturation age, 3 year old under present environment. Catch number between at age 0 and at age 3 of the same year-class in each area show high correlation. It is suggested that the forecast of fishery of yellowtail may possible, if catch number of 0 year old fish in each migration group will be used as one of the index as strength of the year-class. 1-(3) Rearing experiment of pre-larval yellowtail at different water temperature revealed that growth of otholis is faster as water temperature is higher. Comparing this relationship and otholis of larval, juvenile and young yellowtail sampled in the East China Sea and the Sea of Japan, the possibility that spawning ground and period may shift from south of East China Sea in February to western waters of the Sea of Japan in June pointed out recent environment, and may not return to Tohoku region coast again even in summer. It seems that exchange among those migration groups or between migration group and resident group may occur at some probability.