Session C4: Downstream Migration Dynamic of Silver Eel on the Rhine River, Based on RFID Telemetry

Abstract: The European eel stock collapsed in the 1980’s and continues to decline gradually. In 2004, the European Union (EU) council established a management plan and a regulations were initiated in 2007 to improve the recovery of the European stock. In France, an R&D program was launched in 2008 to study and understand the eel’s behaviour and the impact of dams, including hydropower stations. The aim of this study action is (1) to estimate the migration route distribution (power house, spillway, dam, navigation locks) and (2) to study the migration dynamics of the silver eel according to environmental parameters. The NEDAP trail system, based on Radio Frequency Identification method, was used. Between 2010 and 2013, 6 detections stations were operational in the French part of Rhine River, and 2 additional stations have been installed in 2013. This network is connected to the Nedap network in Netherland and Germany. Therefore, eels can be monitored form French part of the Rhine River to the estuary, around 1000 km downstream the release point. Environmental parameters, temperature, turbidity, conductivity are measured at 4 positions on the French part of the Rhine River. On the first hydropower plant (upstream site), all the migration routes are monitored, i.e. power house, navigation locks and spillway. Downstream, a fifth station observes the difference of dynamic migrations between 2 parallel stretches, one with 4 HPP and the other without any obstacle. Between 2010 and 2014, more than 800 fishes have been tagged and released. Eels have been caught in the Rhine watershed, directly in the Rhine River (French part and German part) and in 2 tributaries of The Rhine, Moselle River and Ill River. We analyse the migration dynamic, i.e. migration routes distribution and migration velocity, according to environmental parameters, eel origins and location of the release point. Even if tagged eels comes from the same watershed, migration dynamic is different with the origins. We show that the movement of eels during the 10 days cannot be considered as migration behaviour with this telemetry method. This result has an impact on the migration routes distribution