Japanese Glass Eels Seen Increasing in Hokkaido

Tokyo, Jan. 7 (Jiji Press)--A Japanese research team said Tuesday that glass eels, or baby Japanese eels, are believed to have increased in rivers in Hokkaido, northernmost Japan, in recent years because of an ocean current moving northward due to global warming.

Researchers from the Japan Agency for Marine-Earth Science and Technology, or JAMSTEC, the University of Tokyo and Hokkaido University said the fact that the Kuroshio Current, which flows northward along the Japanese archipelago, is shifting north is believed to be behind the rising prevalence in Hokkaido of glass eels, which mainly grow south of Japan's Honshu main island.

The finding was published in the international oceanography journal Ocean Dynamics the same day.

Glass eels are 5 to 6 centimeters long. They hatch from eggs in waters west of the Mariana Islands and travel on the Kuroshio Current to estuaries on the coasts of Japan, Taiwan and China in winter and early spring.

The research team found glass eels during an investigation of rivers in the Iburi region of Hokkaido from April to July 2021. It used data on the Kuroshio Current and the Oyashio Current flowing south along the Kuril Islands to simulate the movement of glass eels in waters surrounding Japan.

[Copyright The Jiji Press, Ltd.]