Impact of methylmercury on the migratory behaviour, energetic status and detoxification processes in the European glass eel (Anguilla Anguilla): in situ and in experimental studies

• Main Author: Claveau, Julie
• Other Authors: Ecologie Comportementale et Biologie des Populations de Poissons (ECOBIOP), Institut National de la Recherche Agronomique (INRA)-Université de Pau et des Pays de l'Adour (UPPA), Université de Pau et des Pays de l'Adour, Valérie Bolliet
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2014
• Subjects: anguilla anguilla; methylmercury; glass eel; migratory behaviour; these; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDE.MCG]Environmental Sciences/Global Changes; Anguilla anguilla
• Online Access: https://hal.inrae.fr/tel-02801378; https://hal.inrae.fr/tel-02801378/document; https://hal.inrae.fr/tel-02801378/file/Claveau2014_1.pdf

Over the last three decades, the arrival of Anguilla anguilla glass eels has markedly declined which has lead to a decrease in the number of yellow eels in the watersheds. In 2007, the Regulation (EC) indicated that 60% of glass eels (<12cm long) caught by fisheries should be used for restocking. To migrate and colonize a new environment, glass eels must have a good energetic condition. However, during their estuarine migration, glass eels either feed very little or more likely not at all. The speed at which they expend their energy stores depends on various factors (temperature, contaminants etc.). In the Adour estuary, many studies have reported relatively high methylmercury (MeHg) concentrations in the sediments, and bioaccumulation in yellow eels. Exposure to MeHg requires energy for detoxification which, in starving organisms such as glass eels, might lead to weight loss, decreasing their ability to migrate up the estuary. To study the impact of MeHg on migratory behaviour in glass eels, we first conducted an inventory of MeHg concentrations of glass eels in the estuary of the Adour, (2) evaluate the effect of MeHg on two synchronizers of estuarine migration: dusk and tide on glass eels through the use of isotopic tracers and (3) to study the natural environment (Adour) migratory behavior, mercury contamination levels and detoxification mechanisms of glass eels. Our results show temporal and seasonal fluctuations in the concentration of MeHg glass eels collected input and middle of the estuary. Moreover, MeHg exposure, in a controlled environment, increased the activity of glass eels but not in response to migratory behavior. However, due to contamination, mitochondrial structure and metabolism have been modified suggesting a stronger oxidative stress and activation of antioxidant defences of glass eels, particularly those with low migration potential (non-migrant). In addition, the wild study showed a higher energy demand for non-migrating glass eels causing an increase in mitochondrial function which ...