Satellite-tagged eel migration survey

The Institute of Freshwater Biology of Nagano University tagged and released Japanese eels off the coast of Lake Hamana on December 9, 2021, using pop-up satellite tags to track the spawning migration of Japanese eels. In the study, pop-up satellite tags were attached to five silver eels weighing approximately 1 kg (maximum 1.2 kg) caught in Lake Hamana. This will allow continuous behavioral recording of water temperature and depth, as well as measuring the spawning migration route.

This research is being conducted as part of the Fisheries Agency’s International Fisheries Resource Change Mechanism Analysis Project (Eel Unit: Unit Leader: Professor Hiroshi Hakoyama, IFB, Nagano University). The Japanese eel was listed as endangered by the Ministry of the Environment in 2013 and as vulnerable by the IUCN in 2014, raising concerns about its extinction. In addition, the recent decline in Japanese eel catches has become an international issue, and there is a need to accumulate scientific knowledge through CITES considerations, domestic management measures promoted by the Fisheries Agency, and the establishment of an international resource management system (Informal Consultation on International Eel Resource Conservation and Management). In this context, one of the important issues for understanding the resource structure is to track the spawning migration of Japanese eels, to link their nursery and spawning grounds, and to identify the origin (habitat) of the parent eels that contribute to reproduction.

The silver eels used in the research were provided by Ebisen, a seafood broker in Lake Hamana. As part of efforts to conserve eel resources in Lake Hamana, a stocking project is being conducted by the Lake Hamana Eel Release Liaison Committee, and it is hoped that this research will provide baseline data to verify the effectiveness of stocking in Lake Hamana.