Genetic relationships among landlocked, resident, and anadromous Brown Trout, Salmo trutta L.

Abstract

Coexisting freshwater resident and anadromous (sea-run migratory) Brown Trout, Salmo trutta L., were compared genetically with landlocked populations (i.e. living above impassable waterfalls) in the same drainage system in western Norway. No genetic differentiation was found between resident and anadromous life-history types using the same locality and time for spawning. In contrast, significant genetic differences were found between Brown Trout (irrespective of life-history type) spawning in geographically separate localities, and particularly large differences were found between landlocked Brown Trout and those from localities accessible from the sea. These results are consistent with other multiple-locus studies of salmonid fishes, showing larger genetic differentiation between localities than between coexisting life-history types that differ in morphology and ecology.