tIn this study we developed a novel methodology based on fish communities to assess the ecologicalpotential of central European reservoirs. Using the hindcasting approach, our index predicts values thatcould be observed in the absence of pressures for each reservoir depending on their environmental char-acteristics. Fish data were collected from 144 French and Czech reservoirs between 2005 and 2013 bystandardized benthic gillnet sampling and transformed to functional and taxonomical metrics. After allvalidation by multiple testing of models redundancy and pressure-response, the final index was com-posed of three metrics: total biomass of fish, abundance of invertivores/piscivores, and abundance ofplanktivorous fish. The index accurately identifies reservoirs that are lightly, moderately and heavilyaffected by eutrophication. In addition to French and Czech reservoirs, this index could be a useful toolfor countries with few reservoirs and the basis for further collaborative studies.