Interspecific competition between stream‐dwelling brown trout and Alpine bullhead

摘要: Density and composition of benthic invertebrates the diet brown trout Salmo trutta Alpine bullhead Cottus poecilopus were studied at two sites in one Norwegian stream. The separated by an impassable waterfall, density was five to 10 times higher upper, allopatric site than downstream where it lived sympatry with bullhead. Benthic invertebrate communities did not differ between sites; however, size distribution chironomids trichopterans skewed towards lighter individuals sympatric site. Diet suggested that foraged more on drift from surface trout. significantly diet, except fed heavier individual prey within a few taxa consume chironomid pupae or insects. collected data support hypothesis living feed locations predation risk, which is probable explanation for their lower population density.