Distribution of naturally recruited wild Japanese eels in Japan revealed by otolith stable isotopic ratios and document investigation

Abstract

To clarify the natural distribution of Japanese eels in Japan, otolith oxygen and carbon stable isotope analyses were conducted by analyzing collections of data on Japanese eels in scientific archives. The stable isotope analyses can segregate naturally recruited eels from stocked eels. As a result, coastal regions of the whole area of Kyushu, the Seto Inland Sea, the Pacific side south of Aomori Prefecture, and the Sea of Japan side south of Kyoto Prefecture were identified as main areas of natural distribution, and coastal regions from Fukui Prefecture to Aomori Prefecture facing the Sea of Japan were identified as marginal areas of natural distribution. Even in the main area, some rates of naturally recruited eels were less than 30%, suggesting that the eel resources inhabiting Japanese rivers and lakes are dependent on stocked eels.