Problematic: Which type of fish passes (FPs) are appropriate for small hydropower plants (HPPS) in Greece, based on their local characteristics (and thus, using the experience of the German experience)? Elaborate a decision making tool. Investigate dimensionless parameters for the generalization of the German experience on the topic. It will answer the following questions: What kind of FPs are used in Germany? Only conventional FPs will be considered (the ones that have shown that it works) and not special ones. Which type of FPs are suitable for small HPPs in Greece, which have a head difference of approx. 5-12 m (e.g. vertical slot)? What information on flow, fish species, design data, photos etc. need to be collected?