Diadromous fishes are migratory and cross-border resources: they move between fresh and marine waters and their populations share individuals between river basins, crossing administrative boundaries (e.g. states, countries). Diadromous fishes are threatened by various human activities and climate change. A generalized decline has been noticed for many species with, in some cases, a climate-induced shift in the species ranges. The situation is obviously changing, causing new socio-economic and ecological interactions among territories to appear. Consequently, a transnational approach is required in Europe and elsewhere to account for and facilitate these spatial changes in fish populations through better-adapted management plans, and ease the adaptation of territories in the face of climate change. As a consequence, DiadES, a recently-funded European project, will bring together ecologists, economists and key stakeholders from the five European member states bordering the Atlantic Ocean, i.e. France, Portugal, Spain, U.K. and Ireland, to start a joint valuation of ecosystem services associated to diadromous fishes and their potential evolution under climate change. DiadES adopts the innovative approach to convert fish abundances into monetary units, thus circumventing the difficulty to orientate public decision on diadromous fish management with only observed numbers of fish or stock estimates from models. DiadES is a multi-species initiative but its methodologies will be presented through the Allis shad (Alosa alosa) case study. Among the ecosystem services provided by diadromous fishes, the transfer of matter, nutrients and energy operated by these fishes between the continental and marine domains is directly connected to food-web functioning and thus to ecosystem state (Limburg and Waldman, 2009). Even being a widely recognized process, few quantitative estimates of this fish-based nutrient flows exist. The application of the mechanistic species distribution model (GR3D) could help in estimating such transfer at large spatial scale and under past, present and future climatic conditions. Allis shad (Alosa alosa), and its American counterpart, the American shad (Alosa sapidissima), could benefit of such model-based estimates, with arising conclusions on fish and ecosystem management being strengthened by this comparative approach.