回遊性資源の来遊量指数

Abstract

This paper proposes an abundance index of immigrants in exploited migratory populations. The abundance index is derived, as an example of adult yellowtail population immigrating into coastal areas along the main land of Japan in the Japan Sea, on the following assumptions. First, the adult yellowtail population immigrates into the Sea through the Straits of Tsushima and migrates northward along the main land. Second, fishing effort is constant in each fishing area over a period in question. Third, exploited rate is independent of the size of the im-migrant population in each area. Here the exploited rate in an area is defined as the ratio of catch to the immigrant population size into coastal areas along the main land. Finally, the rate in each area is independent of the ones in others and follows a log-normal distribution. As a numerical example, the derived index is applied to the adult yellowtail population along the main land of Japan in the Japan Sea. In addition, this paper compared the index with the one proposed by Hara.