What are the best upland river characteristics for glass eel restocking practice?

• Published in: Science of The Total Environment
• Main Authors: Nzau Matondo, Billy, Benitez, Jean-Philippe, Dierckx, Arnaud, Renardy, Séverine, Rollin, Xavier, Dylan, Colson, Loïc, Baltus, Vasthi Rose, Myrielle Romain, Ovidio, Michaël
• Other Authors: FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège, AFFISH-RC - Applied and Fundamental FISH Research Center - ULiège
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2021
• Subjects: Restocking; Freshwater Ecosystem; Capture Marck Recapture; Endangered fish; Species Conservation; European eel; Life sciences; Aquatic sciences & oceanology; Sciences du vivant; Sciences aquatiques & océanologie; Anguilla anguilla
• Online Access: https://orbi.uliege.be/handle/2268/259190; https://orbi.uliege.be/bitstream/2268/259190/1/STOTEN_NzauMatondoetal2021_eel_restocking.pdf; https://doi.org/10.1016/j.scitotenv.2021.147042

peer reviewed The fitness of restocked European eel (Anguilla anguilla), an endangered fish species, was studied in relation to the environmental variables of habitats in six upland rivers that are typologically different in terms of their hydromorphological and physicochemical characteristics, food resources and fish communities. These rivers received a total of 76,370 imported glass eels in 2017. During a three-year period, we monitored eels with respect to total length, annual growth rate, condition factor and density using capture-mark-recapture experiments to understand the effects of the characteristics of receiving rivers on restocking success levels. Our results showed the survival of the restocked eels in the six rivers and revealed significant differences between them in terms of total length, condition factor and density. Better performance in eel yield variableswas observed in a eutrophic alkaline river with greater roughness of riverbed substrates, dominant pool- and riffle-type flowfacies and lower brown trout density. The variables conductivity and total hardness had higher explanatory power and were strongly associated with increased eel density. This study suggests that a well-selected habitat/river in a restocking programme can be beneficial for the species and recommends restocking practice as a management tool to achieve eel conservation goals.