The impact of fisheries is of great importance on biological, economic, social and political levels. There is still a high uncertainty about the relationships between climate, fish and management decisions. This dissertation provides methodological contributions to several of the data analysis activities necessary to reduce this uncertainty. Firstly, this dissertation deals with finding a trade-off between the performance and the number of zooplankton taxa to classify. The contribution in this domain is a wrapper method where the expert can evaluate the training set in terms of this...