The interspecific competition between brown trout (Salmo trutta L) and rainbow trout (Oncorhynchus mykiss Walbaum): Influence on habitat models

The influence of interspecific competition on the occupation of physical habitat of the Estibere stream was studied in two rainbow trout populations (Oncorhynchus mykiss), one in allopatry and the other in sympatry with brown trout (Salmo trutta L.). The occupation of the Weighted Usable Area (WUA) was calculated by the PHABSIM model of the IFIM methodology (BOVEE, 1982). The occupation by rainbow trouts was significantly greater (t test, p < 0.05) for the allopatric population than for the sympatric population. Surface of cover, gradient and the occupation of the physical habitat by adults of brown trout explained 77% of the variation of the occupation of the physical habitat by rainbow trout. For the adults of brown trout, the surface of cover explained 81% of the variation of the occupation of physical habitat. Interspecific competition may influence the occupation of physical habitat by the different species and life-stages.