An Eel`s Life: Stock Assessment and Estimation of Silver Eel Escapement in a German Eel Management Unit with Intense Stocking

A combined methodological approach, including analyses of fishery datasets, field surveys, stocking experiments, and monitoring of local sub-stocks, was applied to estimate population parameters as recruitment, growth, and mortality rates to aid eel stock assessment in a tributary to German EMU Elbe. In the study area recruitment has been dominated strongly by stocking of 4.4 Mio. young eels as opposed to an estimated natural immigration of 33,000 elvers per year on average. Natural mortality was estimated to account for 86% of total yearly losses in the stock. With 13%, fishing (including angling) ranked highest among anthropogenic mortality causes. When parameterizing the German Eel Model by estimates obtained from our studies, the current number of annually produced silver eel was computed to reach 44,000 individuals, corresponding to 0.4 kg ha^-1. This compares to a silver eel escapement estimate of 19,000 specimens from a mark-recapture-study. Possible reasons for this deviation are discussed.