IMPORTANCE OF ARTIFICIAL BACKWATERS FOR J UVENILE FISH RECRUITMENT INA HEAVILY REGULATED LARGE RIVER, THE LOWER-RHONE

During the last century, submersible dikes have been built in the main channel of the Lower Rhone River. A comparison of the juvenile fish a ssemblages of the channel, of 10 dike fields and 2 dead arms, showed a clear faunistical distinction between these sites dike fields were qu alitatively and quantitatively the richest. We found that juvenile ric hness in these biotopes depends on habitat diversity and submersion ra te. The abundances of the 7 main species were also influenced by at le ast one of the 10 variables that described these sites. Thus, the dike fields now play a major role as nursery sites instead of the ancient floodplain, and contribute in maintaining fish biodiversity in this ar ea.