The mediterranean barbel, Barbus meridionalis (Risso, 1827), is currently classified as a near threatened species by the IUCN. For the purpose of instream habitat management and in order to determine the environmental flows requirements of this species we recently developed univariate Category Three preferences curves for use within the Instream Flow Incremental Methodology (IFIM). In two Mediterranean rivers of south of France a total of 883 Mediterranean barbel was collected at 406 electrofishing units, and measurements of local substrate and hydraulic features were performed. The 5M7 model was used to build the river-specific trajectories of the Mediterranean barbel in the (depth, mean velocity, total fish length) space. This model was then improved with the inclusion of a new system of species-environment equations. This revealed that the river-specific trajectories can be predicted by applying preferences curves related to the mean total length of each life stages to the river specific hydrosignatures. Results also indicated that the preferences curves of another Barbel species, Barbus barbus (Linnaeus, 1758), were compatible with the Mediterranean barbel trajectories. This new approach represents a valuable tool to assess the transferability of preferences curves and in a general way to assess the efficiency of fish habitat models.