European eel distribution and body condition in a river floodplain: effect of longitudinal and lateral connectivity

• Published in: Ecology of Freshwater Fish
• Main Authors: Lasne, Emilien, Acou, A., Vila-Gispert, A., Laffaille, P.
• Other Authors: Biodiversité et gestion des territoires EA 7316, Biologie des organismes marins et écosystèmes (BOME), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), DIREN Pays-de-la-Loire; Agence de l'eau Loire-Bretagne; Conseil Regional Pays-de-la-Loire
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2008
• Subjects: Anguilla anguilla; body condition; lateral connectivity; distribution; large river; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDV.EE]Life Sciences [q-bio]/Ecology; environment
• Online Access: https://hal.science/hal-00440331; https://hal.science/hal-00440331/document; https://hal.science/hal-00440331/file/Lasne%20et%20al.%202008%20EFF_1.pdf; https://doi.org/10.1111/j.1600-0633.2008.00307.x

International audience We studied eel population characteristics (size classes, densities and body condition) in the lower Loire River floodplain (France) to evaluate the effects of longitudinal and lateral gradients. A total of 36 sites were electrofished in June 2005. The sites were grouped first into three river segments according to the distance inland corresponding to a longitudinal gradient and secondly into three lateral connectivity categories. Results indicate that small eels, especially those ≤300 mm, were very abundant downstream but density rapidly decreased upstream. In addition, eels ≤150 mm tended to be most abundant in connected waterbodies. Conversely, the distribution of larger eels was quite uniform across both dimensions. Eel condition decreased upstream. In parallel, in downstream river segment, eels had a lower condition in disconnected waterbodies than in connected ones. Eel specialists still have only a longitudinal perception of eel habitat. Our results suggest that lateral gradients should be also taken into consideration