Abstract
Studies on the effects of introduction of species have mainly focused on introduction of exotic species. However, introductions across smaller geographical scales with species that naturally coexist in other regions of the species' geographical distribution are probably more common, particularly for the commercially important freshwater fishes. The project will study the effect of introducing Atlantic salmon into parts of rivers with brown trout as the only fish species. The project will study effects of the introduction on the morphology and behaviour of the closely related brown trout, and cascading effects on other organisms in the ecosystem, exemplified by the freshwater pearl mussel - a species that depend on the presence of salmonids for reproduction. The field studies aim at studying morphological variation and habitat use of brown trout in populations living in allopatry and in sympatry with salmon. For the freshwater pearl mussel the field study will explore the presence of host specific populations in different parts of rivers. In the lab the project will experimentally study morphological selection gradients on brown trout in the presence and absence of salmon, and to what extent freshwater pearl mussels from different populations within the same river system are host specific.
Norway