Survey of downstream migration of silver eels through discharge pipe on a reservoir dam

• Main Authors: Legault, A., Acou, Anthony, Guillouët, J., Feunteun, E.
• Other Authors: Fish Pass, Pôle OFB-INRAE-Institut Agro-UPPA pour la gestion des migrateurs amphihalins dans leur environnement (MIAME), Université de Pau et des Pays de l'Adour (UPPA)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Office français de la biodiversité (OFB)-Institut Agro Rennes Angers, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Patrimoine naturel (PatriNat), Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Office français de la biodiversité (OFB), Ecosystèmes, biodiversité, évolution Rennes (ECOBIO), Université de Rennes (UR)-Institut Ecologie et Environnement - CNRS Ecologie et Environnement (INEE-CNRS), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), LABORATOIRE DE BIOLOGIE ET D'ENVIRONNEMENT MARIN LA ROCHELLE, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)
• Format: Article in Journal/Newspaper
• Language: French
• Published: HAL CCSD 2003
• Subjects: Anguilla anguilla; silver eel; downstream migration; management; migration; dévalaison; aménagement; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Joli
• Online Access: https://hal.science/hal-04611118; https://doi.org/10.1051/kmae:2003035

International audience The survey of the catadromous migration of eels through a major dam was operated on a pipe insuring a minimal legal discharge of the dam of Bois Joli on the Frémur River (Northern Brittany, France : height, 13.7m Volume, 3 Millions of m3). Part of the silver eels used this pipe to emigrate, at the beginning of the downstream run when it represented the only possible downstream passage, but also later when the dam spill enabled a second emigration pathway. Because of the low discharge and of the design of the pipe, it is assumed that eels look for a possible seawards passage. Downstream passage through the pipe was estimated to represent 12% of the downstream run and thus contributes significantly to the transit of silver eels. The contribution of the migration pathways to the migration runs are thought to depend uponthe water discharge. Despite its modification to facilitate emigration, the discharge pipe induced the mortality of 11% of migrating silver eels. Mortality was mainly due to abrasion. In many cases, passage through discharge facilities probably induces high or even total mortality depending upon management options, characteristics of the dam and design of the discharge facility. This induced mortality is likely to reduce significantly the production of breeders by river systems. Marked eels that passed the dam before the emigration peak stopped for a few weeks to one year. This observation confirms that reservoirs decreases migrations speed and efficiency. The dams and other works should be managed in order to facilitate passage and reduce mortality of emigrating silver eels.