A complete check-up of European eel after eight years of restocking in an upland river: Trends in growth, lipid content, sex ratio and health status

• Published in: Science of The Total Environment
• Main Authors: Nzau Matondo, Billy, Delrez, Natacha, Bardonnet, Agnes, Vanderplasschen, Alain, Joaquim-Justo, Célia, Rives, Jacques, Benitez, Jean-Philippe, Dierckx, Arnaud, Séleck, Emilie, Rollin, Xavier, Ovidio, Michaël
• Other Authors: UNIVERSITY OF LIEGE UR FOCUS BIOLOGY OF BEHAVIOUR UNIT LABORATORY OF FISH DEMOGRAPHY AND HYDROECOLOGY LIEGE BEL, 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), Immunology-Vaccinology, FARAH, Université de Liège, Ecologie Comportementale et Biologie des Populations de Poissons (ECOBIOP), Université de Pau et des Pays de l'Adour (UPPA)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratory of Animal Ecology and Ecotoxicology, SPWARNE-DNF-Public Service of Wallonia - Agriculture, Natural Ressources & Environnement, Wildlife & Forestry Department, This research was funded by the‘Definition of the scientific andtechnical bases for an optimisation and evaluation of the efficiency ofEuropean glass eel (Anguilla anguilla) restocking practices’projectfinan-cially supported by the European Maritime Affairs and Fisheries Fundand the Wallonia Public Service, under Grant numbers FEAMP No. 44-1604-008 Glass eel and 44-1604-009 Eel4ever projects)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: Life history traits; AngHV-1; Phenotypic sex; Organic pollutants; Freshwater ecosystems; Endangered species; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDV.EE.ECO]Life Sciences [q-bio]/Ecology; environment/Ecosystems; European eel
• Online Access: https://hal.inrae.fr/hal-03470887; https://doi.org/10.1016/j.scitotenv.2021.151020

International audience By combining field research and careful laboratory analysis of samples over the course of an eight-year study, we met the challenge of assessing the life history traits and health status of eels restocked in freshwater ecosystems. We found that restocked eels exhibited good growth performance; moreover, the stocks were female-dominated, showed a good Fulton's condition factor (K) and lipid stores and had high survival probability estimated using the best model of Jolly-Seber stock assessment method for open populations. A necropsy revealed the absence of internal lesions. A swim bladder examination revealed the absence of the parasite Anguillicola crassus. Polymerase chain reaction (PCR) analyses revealed an increase of Anguillid herpesvirus-1 (AngHV-1) prevalence throughout the study. Most positive subjects expressed viral loads compatible with a latent infection and correlated positively with K. All restocked eels were contaminated by at least one of the organic pollutant congeners studied, but the pollution loads corresponded to the lowest range of pollutant concentrations reported in the available literature for European eels and did not exceed the maximum residue and contaminant limits in food and feed of several national and international regulations. Pollutant loads were negatively correlated with K, lipid content and eel density for polychlorinated biphenyls PCB 138, 153 and 180 and K for pesticides p.p’-DDE, p.p’-DDD, p.p’-DDT and PBDE47. This study highlights the potential role played by upland aquatic ecosystems in enhancing riverine silver eel production from the perspective of species conservation. To be successful, restocking must be accompanied by improved ecosystem quality and migration routes for eels in inland freshwaters. We also provide some recommendations for future research to improve the management of restocking programmes.