Lagoons are important habitats for eels and needs to be included in the stock assessment models. But due to their salinity, traditional electrofishing method to estimate densities cannot be used and other methods need to be tested. The objective of this project is to test the enclosure method in a Mediterranean lagoon in order to determine whether this method is applicable for assessing eel densities in lagoon environments. To do this, the system's airtightness was tested using an acoustic network that allows the positioning of tagged eels on a fine scale (VEMCO VPS positioning system). The purpose of this work is to determine, based on the results, whether this method can be applied more widely to other lagoon systems and under what conditions.