Migratory behaviour of glass-eel (Anguilla anguilla) in the Adour estuary according to variability of environnemental conditions

On the Adour estuary, fishing gear filtered the upper part of the water col umn, only individuals located close to the surface were accessible. Consequ ently factors acting on the migration of glass eels in the water column hav e a great importance, on the fishing success. Experimental sampling data co llected in the Adour estuary since 1996/1997 were used to study glass eels behaviour according to variability of hydroclimatic factors and observed de nsities in near shore and surface layers, to quantify their run flow and to evaluate their rate of exploitation. Vertical migration depends of night b rightness and turbidity, speed of horizontal migration in estuary depends t o river flow and tide coefficient level. In front, glass-eels morphometric characteristics were sampled : length. we ight and pigmentary age. Adverse, hydrological conditions for migration ind uced additional weight modifications to the seasonal decrease in weight and length. To complete those results and better characterised on eel flow. ph ysiological examination and embryonic past will be undertaken.