Use of passive integrated transponder tags to analyse the behaviour of young eels in specific eel passes and in a multispecies fishpass (#61)
The European eel (Anguilla anguilla), catadromous fish once widespread and abundant, is now the subject of a preservation policy at a European level since 2007. Concerning upstream migration, managers now have technical solutions to enable the migration of young eels with specific passes that demonstrate their functionality, still being improvable. The desire to improve knowledge of fish behavior in fishpasses has led to the installation of passive integrated transponder (PIT Tag) antennas networks associated with significant fish tagging campaigns. Three different kinds of fishways have been monitored, a brush, a studs and a multispecies vertical slot fish pass. More than 5,000 eels have been tagged since 2004 in a brush eel pass (Garonne River), 6,000 since 1999 in a studs eels pass (Dordogne River) and 268 eels in a vertical slot fishpass (Rhine River) in 2014. These data can improve knowledge on the use of the fishpasses by the species in relation to its biology, but also potentially provide solutions for improving the devices. The first results of the brush eels pass suggest that eels generally quickly reach the upstream area but hardly come back if they fail at the first attempt. Eels of the size range tested on the Rhine River do not seem to have any significant difficulties to pass through the vertical slot fishway. Moreover, eels behavior and passage time were compared with existing data with salmonids (2010) and cyprinids (2011-2012) in the same fishway.