| Summary: | International audience Habitat-hydraulic models simulating habitat productive capacity for fish have met with limited success. Limitations of hydraulic modelling, particularly related to spatial scale relevant for hydraulic field data collection and model simulations, have attracted little attention. The hypothesis that hydraulic field sampling procedures and modelling scale per se affect results was tested using three habitat-hydraulic models that employed the same fish habitat data and similar hydraulic models. The PHABSIM, EVHA and HABITAT habitat-hydraulic models were compared on a 5.56 km long, 12-35 m wide , river segment in newfoundland, Canada. Approaches to hydraulic data collection allowed higher spatial resolution in the EVHA and HABITAT models on selected subsegments representing habitat types (with from 12 to 14 transects per subsegment), while the PHABSIM models covered the entire segment but at lower resolution (a total of 14 transects representing four habitat types placed along the enire segment). Habitat-hydraulic modelling results were similar between the PHABSIM and EVHA with respect to flow vs. Suitable habitat curves, but there were important differences between HABITAT and PHABSIM/EVHA. These differences were attributed mainly to different biological models because the hydraulic models performed similary. Weighted usable area (WUA) curves gave less information than separate suitability curves for habitat variables. It is important that habitat-hydraulic data be collected, and model simulations conducted, at scales that are relevant to habitat selection by species and age classes of interest. Les modèles d'habitat physique simulant la capacité d'accueil pour les poissons ont des limites à connaître pour mieux les utiliser et pour les améliorer. On s'est cependant relativement peu intéressé aux limites de la modélisation hydraulique, notamment du fait de problèmes d'inadéquation entre l'échelle spatiale des mesures sur le terrain et l'échelle spatiale des simulations. Dans cette étude, ...
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