Abstract
The understanding of glass-eels (Anguilla anguilla L.) progress in estuary is a complex phenomenon which requires to better analyze their behavioural response towards environmental parameters. Two experiments on the influence of the ligth/dark diel change on glass eel movement were carried out in a flume, during February and March 2000. The upstream and downstream dynamics of catches, as well as some fish characteristics (length, weigth, pigmentary stage) were recorded. Glass-eels were caught mainly by night and in the downstream trap. These downstream catches mean that fish moved with the waterflow, which is in agreement with the hypothesis on selective tidal transport generallly admitted (swimming behaviour adapted to the migration in estuary, where upstream displacement occurs during the flood tide). Fish caught in the traps, (Movers) were slightly longer than fish collected in the substratum (Stayers). In one of the two replicates, movers were also more pigmented and heavier than stayers. Results suggest that swimming activity lasted for 3-4 hours.
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