Out of management reasons, eels are tagged in both freshwater and on the coasts of Sweden. Different tagging methods have been used throughout the years since eel tagging started in 1903. At the time being with minor fishery, acoustic telemetry is suitably to study migrating eels. Receiver lines increases in number yearly, sometimes in cooperation with projects for other species at different locations in the Baltic Sea area and in freshwater lakes. In the near future we also intend to use pop-up satellite tags for further understanding of migration behavior of eels passing through Swedish waters on their way to the spawning grounds.