Acoustic telemetry was used to quantify the behaviour of 94 hatchery-reared European sturgeon (27–38 cm in fork length) released in their native watershed. The study took place between July and December 2008 and between April and May 2009 in the tidal part of the Gironde system (south-west France) from freshwater to mesohaline estuary. Survival rate for the first month was estimated at 87% and the individual trajectory of 82 fish was characterised. The mean distance covered per fish was 104 km, the mean ground swimming speed was 0.7 ms−1and no diel influence was highlighted. Three main downstream migration patterns were highlighted with a first group of individuals settling in the freshwater part of the system, a second group covering medium distances (105 km) and displaying fairly straight movement to reach the upstream estuary, and a third group of very active fish with repeated up and down movements into the mesohaline estuary covering two times more distances. We suspect that these patterns correspond to different exploratory behaviours and salinity tolerances among individuals of the same size and cohort. According to our experiment, both the downstream freshwater part of the rivers and the upstream estuary represent important habitats for this age class. The direction of individual trajectory indicates that most of the fish displaying upstream and downstream movements gradually shifted downstream between 1 and 6 months after their release.