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Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/6178

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Sirvi Artiklid Märksõna "Anguilla anguilla" järgi

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  • Pisipilt
    Kirje
    Conservation restocking of the imperilled European eel does not necessarily equal conservation
    (Oxford University Press, 2021) 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; Institute of Agricultural and Environmental Sciences, Centre for Limnology
    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.
  • Pisipilt
    Kirje
    How do environmental factors affect the yield of European eel (Anguilla anguilla) in a restocked population?
    (Elsevier, 2020) Bernotas, Priit; Öglü, Burak; Nõges, Peeter; Chair of Hydrobiology and Fishery. Institute of Agricultural and Environmental Sciences
    Restocking of European eel (Anguilla anguilla) is a widespread practice throughout Europe. Conditions during restocking activities and mortality related to restocking practices have been discussed, however, factors affecting these restocked populations afterwards are mostly not considered. In this study we used a machine learning method followed by generalized linear model to analyze long time eel restocking, commercial fishery and environmental data from Lake Võrtsjärv, Estonia, to detect whether significant relationships exist within these data. It was found that environmental parameters can have an effect on the commercial eel yield both retrospectively and during the particular fishing year. Considering that 7-year old eel was the most common age group in commercial catch, we introduced a 7-year gap between eel restocking and yield to study the most important abiotic and biotic factors during the first year of eel restocking that have an effect on the yield. According to our results, cyanobacterial biomass and summer water temperature during the year of restocking had the strongest negative impact on the yield 7 years after, while the number of restocked individuals and copepod biomass had a positive effect. During particular fishing year, however, the yield was most notably positively affected by total phosphorous concentration, number of individuals restocked 7 years before and metazooplankton biomass in the lake.