Very few tidal power plants exist in the world. The first one was built in the Rance estuary (Brittany, France) in 1966 and the second one in South Korea. However, with the increasing demand in renewable energy, other tidal power plant projects are being studied. These power plants are larger than unidirectional fluvial hydropower plants and strongly modify the natural tidal cycle in estuarine systems. As such, their effect on megafaunal movements might strongly differ from those caused by unidirectional fluvial hydropower plants and should be specifically considered and studied before the development of similar constructions. In this study, an acoustic telemetry array was deployed to track 25 silver eels released 16 km upstream of the Rance tidal power dam. Only 1/3 of the tagged eels passed the dam and reached the sea. Data suggested that eels interrupted their migration up to 5 km upstream of the dam. We assume that the noise and tidal disturbance generated by the dam could lead to a disruption of a high proportion of silver eels' reproductive migration.