| Summary: | International audience European sea bass is a highly mobile species whose spatial dynamics remain poorly understood. In order to analyze adult migration patterns, we carried out tagging experiments (acoustic telemetry and data storage tags) off the coast of west Brittany. Acoustic tracking provided 3D behaviour used to parameterize a geolocation method from DST data (depth and temperature). To date, 21 DSTs out of 246 have been recovered. Our geolocation model (daily predicted probability maps issued from a HMM - hidden Markov model) combines both satellite SST data and the hydrodynamic model MARS3D, and a sensitivity analysis demonstrates it robustness to recover consistent movement patterns. Fish with long times at liberty exhibited strong site fidelity to summer feeding ground. Reconstructed individual trajectories revealed different spawning migration patterns (mostly in the Bay of Biscay but also in the Celtic sea/English Channel). The joint analysis of horizontal and vertical movements showed seasonal behavioural shifts. Our results support the hypothesis of a fine scale spatial structuring at the population scale, a key issue poorly addressed by current management frameworks. It also provides key information for the understanding and the modelling of the spatial dynamics of the species under environmental forcing.
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