Just go with the flow? Route selection and mortality during downstream migration of silver eels in relation to discharge

• Main Authors: Henrice M. Jansen, Hendrik V. Winter, Maarten C. M. Bruijs, Harry J. G. Polman
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2007
• Subjects: fisheries; hydropower; individual eel behaviour; migration; radio telemetry; river discharge; route selection; silver eels; Anguilla anguilla
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.576.2187; http://icesjms.oxfordjournals.org/content/64/7/1437.full.pdf

The European eel (Anguilla anguilla) has been in steep decline for several decades. Fisheries and hydropower-induced mortality pre-sumably play an important role during the downstream migration of silver eels, and downstream-migrating silver eels must make various navigation and route-selection decisions to reach the sea. We examined the influence of river discharge on route selection of silver eels. To quantify the impact of hydropower and fisheries on silver eel mortality, radio-telemetry experiments were performed in the River Meuse in 2002 and 2004, surgically implanting 300 silver eels with Nedap-transponders. Route selection and passage beha-viour near detection stations was assessed. Silver eels were distributed over the alternative migration routes in the river in proportion to the discharge until the silver eels reached the entrance to the turbines. The eels altered their behaviour when approaching the turbines of hydropower plants and showed stationary and recurrent behaviour. We discuss the consequences of this on route selection and mortality rates caused by hydropower facilities and fisheries.