The relationship between migration behavior and energetic status in the European glass eel (Anguilla anguilla)

• Main Author: Liu, Hengtong
• Other Authors: Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Université de Pau et des Pays de l'Adour, Valérie Bolliet
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2020
• Subjects: Anguilla anguilla; Glass eel; Facultative migration; Metabolism; Autophagy; Methylmercury; Stress; Civelle; Migration facultative; Métabolisme; Autophagie; Méthylmercure; [SDV.BC]Life Sciences [q-bio]/Cellular Biology
• Online Access: https://tel.archives-ouvertes.fr/tel-03411097; https://tel.archives-ouvertes.fr/tel-03411097/document; https://tel.archives-ouvertes.fr/tel-03411097/file/thesishengtongliu.pdf

Résumé en anglais : The European eel (Anguilla anguilla) present a complex life cycle with a glass eel stage migrating up estuary to reach river for growth. However, this estuarine migration is known to be facultative, with some individuals settling at sea, in estuaries or alternating stays in rivers and estuaries. As glass eels feed little or not at all during their migration, their divergent migration patterns may be closely associated with individual’s body condition. To date, one major theory of conditional strategy proposed that the facultative migration in European glass eels is based on energy stores, the individuals with a high migratory capacity presenting high energy stores. However, this theory has been proved controversial and the aim of this thesis was to investigate the conditional strategy in European glass eels based on more comprehensive measures of energetic status, including not only energy stores but also energy mobilization (metabolism and energy-related genes expression). We also focused on both autumn and spring glass eels, which present dramatic difference in energy stores. We first characterized the individual energetic status of marine glass eels sampled in autumn and spring and related this status to their migration behavior assessed in experimental facilities. Autumn glass eels presented higher energy stores and a higher ability to produce energy than spring ones. This confirmed that autumn and spring glass eels present strong differences in their energetic status and that they have to be studied separately. We hypothesized that a potential threshold in energetic status may exist below which migration could be conditioned by energetics. Then, to unveil the underlying mechanisms of settlement processes in estuaries in relation to energy-based conditional strategy, we investigated the relationship between energetic status and migration behavior in both marine and estuarine glass eels. Estuarine individuals displayed lower weight than marine ones in autumn but not in spring supporting ...