Acoustic telemetry data of silver eels during their downream migration from the River Mondego (Portual). Escapement rate was estimated during two consecutive spawning seasons (2014-2016) and their migratory behaviour was studied. 47 silver eels (males and females) were tagged with acoustic transmitters and their migration was monitored with automatic receivers (VR2W - listening at 69kHz) deployed at four locations along the river course, from the first impassable obstacle (downstream Raiva Dam) up to the river mouth (67 km).