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, Agnès, Vanderplasschen, Alain, Joaquim-Justo, Célia, Rives, Jacques, Benitez, Jean-Philippe, Dierckx, Arnaud, Séleck, Emilie, Rollin, Xavier, Ovidio, Michaël
• Other Authors: FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège, AFFISH-RC - Applied and Fundamental FISH Research Center - ULiège, FARAH - Fundamental and Applied Research for Animals and Health - ULiège
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2022
• Subjects: Life history traits; AngHV-1; Phenotypic sex; Organic pollutants; Restocking; European eel; Life sciences; Environmental sciences & ecology; Sciences du vivant; Sciences de l’environnement & écologie
• Online Access: https://orbi.uliege.be/handle/2268/264482; https://orbi.uliege.be/bitstream/2268/264482/1/Soten_eel_NzauMatondoetal_2022.pdf; https://doi.org/10.1016/j.scitotenv.2021.151020

peer reviewed 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 femaledominated, 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 swimbladder 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 aquaticecosystems 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.