The overall aim of the project is to evaluate the role of acoustic telemetry in improving the assessment of the European eel, with a focus on the Mediterranean stock, for which recent assessments highlight coastal lagoons as key habitats. The selected pilot site is the Orbetello Lagoon (Italy), one of the largest basins in the western Mediterranean, where eel fishing has significant economic and cultural importance. Acoustic telemetry is combined with a mark–recapture survey to quantify silver eel escapement from the lagoon. In addition, yellow eels were tagged to investigate habitat use and seasonal spatial behaviour. A total of 11 receivers (NexTrak R1) were deployed, and 250 eels were tagged with Innovasea transmitters selected according to animal size (V9, V8, and V7). The results will help refine population estimates and validate key assumptions and the accuracy of the Mediterranean eel stock assessment model (ESAM 3.0), supporting the definition of management measures to regulate fishing activities