German Eel Model (GEM III) -a Size and Age-Structured Model for Describing the Dynamics of Male and Female Eel Stock, Anguilla Anguilla (L.), in the River Elbe System

The eel, Anguilla anguilla (L.), stock of the river Elbe severely decreased during the last decades. Detailed knowledge of the stock dynamics in freshwater and especially of the impact and mortality factors is necessary to take effective measures for stock conservation and improvement. The dynamics of the male and female eel stock are modelled based on immigration, stocking, natural mortality and mortalities caused by fishing, angling, cormorants and hydropower plants. In addition, the effect of “catch & carry” in barrier-free water bodies is taken into account. The model estimates the number and biomass of emigrating eel. Moreover, it enables to study the sensitivity of the estimates related to the uncertainty of the source data of the different influencing factors. The model may be used to develop management strategies and to assess the efficiency of different management options.