Since 2018, an acoustic camera monitors the escapement of silver eels in the channel of Port la Nouvelle that is linking the lagoon of Bages-Sigean to the sea. During the migration period, we observed that some of the eels are moving towards the lagoon. As acoustic camera images do not allow to differentiate between yellow eels (which remain in the lagoons to grow) and silver eels (future spawners that escape from the lagoons to the Mediterranean Sea), a telemetry study was set up to determine if these eels could be yellow eels that reside mainly in the port and occasionally move to the lagoon or reside mainly in the lagoon and occasionally move to the port.