MULTI-SCALES APPROACH OF THE RELATIONSHIP S BETWEEN BROWN TROUT (SALMO-TRUTTA L) POPULATIONS AND HABITAT FEATURES IN THE CENTRAL PYRENEES

The influence of spatial scales, of reach, of sequence and morphodynam ic units on occupation by trout populations of the physical habitat ca lculated by IFIM methodology was studied on 264 morphodynamic units of 15 streams of the Central Pyrenees (France). A variance analysis mode l explained respectively 51.1% and 69.8% of the variability of the occ upation of physical habitat by total density and by total biomass of t rout. The results are discussed in relation to the interest of multi-s cales approach for the carrying capacity concept of salmonid streams a nd the relation between biological processes and spatial scales.