| Summary: | The eel (Anguilla anguilla L.) is a fish that is mainly found in European waters. The River Moselle is among the bodies of water inhabited by this specimen. During the downstream migration into their Atlantic spawning ground, silver eels often experience severe to fatal injuries while passing the turbines at the barrages. This annual migration takes place in a relatively narrow timeframe. Therefore, knowing the trigger or beginning of said migration, the mortality rate of the eels could be reduced by a fish-adapted turbine control or comparable protective measures. This thesis introduces an early warning system, which predicts the periods of silver eel emigration by means of certain abiotic factors. On the basis of the information gleaned from different studies and the experience gained from many years of professional fishing, those environmental factors were identified which are connected with the migration of the silver eel. Extensive data analyses were used to substantiate these findings. The water flow, the flow differences and the lunar phase were particularly relevant. Furthermore, the season and the water temperature were taken into account. In view of the different sources of information (experience and expert knowledge, data sets and the findings derived from it), a hybrid structure of the early warning system was realized. After examining different methods from the fields of soft computing and mathematics or statistics, the fuzzy logic (knowledge-based), the case-based reasoning (casebased) and the artificial neural networks (data-based) were selected. With each of these methods, an independent prediction model was designed, tested and optimized. Special characteristics were found during the data analysis and were taken into account by the use of adequate modifiers. The models were tested on the basis of the present data sets for the Moselle. It was shown that it is possible to correctly predict most of the situations with increased catches (suggesting a migration). Threshold values for a migration ...
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