This paper presents an integrative approach to define the migration status of Salmo Salar and Anguilla Anguilla in various scales (work scale, site scale, global scale) according to the results of on-site studies led on the low Belgian Meuse river. According to the stocks repartition, fishes are introduced in the model along each reach. The losses along the reaches are than evaluated according to the loss percentages observed during the on-site fish tracking. On each site, composed by several

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... ructures (dam, sluice, hydropower plant, and/or industrial water intake), the fish repartition is realized according to the repartition observed in the tracking studies. A correction of these values is also proposed based on the literature to take into account variations of the river discharge. The fish survival related to the turbines is than applied to the part of the stock passing through the plant. This enable to define the part of the stock passing the site safely to the next reach. This approach provides results in terms of fish survival in each structure, on each site, and globally downstream the whole studied area. It also enables to analyze the sensitivity of the global system response function of the expected effectiveness of local solutions for downstream migration such as turbine replacement, predictive models, behavioral barriers and downstream fish passes.