千葉県の漁獲高に及ぼすエル・ニーニョの影響

概要

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The catch in the seas near Honshu, the main island of Japan, fluctuates significantly in accordance with the occurrence of ENSO events. This is not clear in the open seas. It is considered that the catch depends closely upon the conditions of the Kuroshio currents near Japan. An example is given by the Pacific saurel and mackerel in Chiba Prefecture on the Pacific side of Honshu, Japan. In most El Nino years, the catch decreased, but more significantly is the increase in the next years of the El Nino event. The average of saurel caught increased in the five cases after an El Nino year to the next year was 14,700 ton and that of mackerel was 18,600 ton. Such phenomena seem to be caused by the negative effect for the catch in the El Nino years, which resulted in the change of spawn regions in the seas under the influence of the Kuroshio current affected by the El Nino event. It was also shown that sardine catch decreased sharply in the El Nino years and recovered in the next years. In the La Nina years, the tendencies were reversed. These tendencies, however, were different between the periods of low level (total catch less than 800,000 ton) and high level in the long-term cycles of sardine catch for example.