Conservation restocking of the imperilled European eel does not necessarily equal conservation

• Published in: ICES Journal of Marine Science
• Main Authors: Rohtla, Mehis, Silm, Maidu, Tulonen, Jouni, Paiste, Päärn, Wickström, Hakan, Kielman-Schmitt, Melanie, Kooijman, Ellen, Vaino, Väino, Eschbaum, Redik, Saks, Lauri, Verliin, Aare, Vetemaa, Markus
• Other Authors: Institute of Agricultural and Environmental Sciences, Centre for Limnology
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Oxford University Press 2021
• Subjects: Anguilla anguilla; eel management plan; migration; otolith microchemistry; provenance; articles; Narva
• Online Access: http://hdl.handle.net/10492/8001; https://doi.org/10.1093/icesjms/fsaa196

To stop the decline of the European eel population, one of the measures taken is translocating eels for restocking, despite its conservational value being largely unknown. We aimed to contribute to this knowledge gap by (i) investigating the origin of eels caught in coastal waters of Estonia and Finland using otolith microchemistry and (ii) directly estimating restocked eel escapement from Narva River Basin District (NRBD), which is part of the primary Eel Management Unit in Estonia. In Estonia, 74% of the sampled eels (n ¼ 140) were natural recruits and 26% were restocked. In Finland, 27% of the sampled eels (n ¼ 235) were natural recruits and 73% were restocked. Only 1% of all the coastally collected eels were originally restocked to NRBD. These new data together with the reported commercial landings from the escapement route conflict with the current silver eel escapement estimation for NRBD and question the accuracy and value of such indirect calculations com- piled for most Eel Management Units throughout the European Union. It is concluded that restocking eels to freshwaters may be futile as a conservation measure in some situations, and better escapement is likely achieved in restocking eels to coastal waters or undammed freshwa- ter systems with a direct connection to the sea. This is Vegacenter publication no. 033. M.R. received financial support from the Norwegian Research Council (project MAREEL #280658). We thank all the people who participated in sample collection. We also thank two anonymous reviewers for their con- structive comments on the manuscript. This is Vegacenter publication no. 033. M.R. received financial support from the Norwegian Research Council (project MAREEL #280658). We thank all the people who participated in sample collection. We also thank two anonymous reviewers for their con- structive comments on the manuscript.