Assessing the yellow eel stock in a river catchment is required to quantify the impact of anthropogenic pressures and to prioritize management actions. EDA model (Eel Density Analysis), coupling a GIS approach and a statistical eel distribution model, was used as the standard tool during for French national Eel Management Plan implementation. We propose an alternative model named TABASCO for "spaTialised Anguilla Basin colonization assessment model" to overcome some of the limitations of EDA, especially regarding the modelling of weirs impacts. TABASCO is halfway between strictly statistical approaches and mechanistic models. Two versions of the model were developed in parallel. The first one is based on the spreading of a Gaussian distribution through a graph to model a diffusive process. The second implements a more mechanistic and more rigorous vision of the diffusion, simulated with a transition matrix. Both approaches are tested on the Garonne-Dordogne Basin (South west of France). Comparison of simulations with or without obstacles highlights the relative impact of migration barriers in that area.