Migration Dynamic of Silver Eel in the Rhine River: Importance of Eel Origin and Release Locations

The European eel population has been declining since the 1980s. Hydro stations have been identified by the European Council as one of the causes of the stock decline. The aim of this study is to analyse the migration dynamic of the silver eel according to environmental parameters and to estimate the migration routes distribution on a river with hydro stations. The monitored river is the French part of the Rhine River, 100 km long and equipped with 10 hydropower plants. Upstream, Rhine River is divided in 2 parallel sections, one with 4 hydropower plants and one without any obstacle. Eels are monitored with the NEDAP trail system, based on RFID technology, well adapted to large rivers. Downstream the confluence, an antenna compares the migration dynamics in the 2 sections. At the most upstream hydro station, every migration routes are covered (i.e. power house, locks, dam). Environmental parameters, such as temperature, turbidity and conductivity are measured at 4 positions. From 2010 to 2013, around 400 eels, caught in the Rhine River and 2 tributaries, have been monitored. We analyze the migration dynamics according to environmental parameters, origins of eels and locations of release points