Eels at the Edge: Science, Status, and Conservation Concerns

Present Status of the Japanese Eel: Resources and Recent Research

Katsumi Tsukamoto, Jun Aoyama, and Michael J. Miller


Abstract.—The Japanese eel, Anguilla japonica, is an important food fish in East Asia, and catches of glass eels and of eels in freshwater appear to have declined dramatically in recent decades, causing increasing concern for the health of wild stocks. During that time, research efforts to understand its biology have progressed considerably. The spawning area was successfully outlined to the west of the Mariana Islands in 1991, and other research suggests that their recruitment success may be related to El Niño events, which appear to affect the transfer of leptocephali from the north equatorial current into the Kuroshio Current. Otolith microstructure and microchemistry studies have revealed various aspects of their early life history that relate to their oceanic larval migration. The discovery of sea eels that live in marine habitats without entering freshwater may change the common understanding of freshwater eel ecology and affect management plans. Most genetic studies suggest that the Japanese eel is composed of a single panmictic population throughout East Asia. Therefore, international management is needed among the countries of China, Taiwan, Korea, and Japan, where glass eels recruit from a common stock and are used extensively for aquaculture.