The objective of this study is to determine the general features of civelle migration in Gironde estuary from CPUE time series collected from the more cooperative professional fishermen daily reports. We use spectral method and multivariate analyses to strengthten previous results. This phenomenon is influenced not only by tide coefficient (migration vector), but also by temperature and freshwater flow (migration inhibitor). A first modelisation is attempted with a simplistic reactor including a cryptical stock on estuary bottom. The tide coefficients action are approximated by a linear function, the temperature and the flow by logistic functions.