Age structure and growth of wild brown trout in relation to population density and habitat quality

Brown trout Salmo trutta L. is a fish species with high socio-economic value, which is favourable among anglers and a successful invader worldwide. The aim of this thesis is to explore environmental factors affecting body growth and survival of brown trout with emphasis on density dependent selection in juvenile life stages. This thesis is specifically focused on: (1) effect of population density on growth and survival with respect to a dynamic of a local group of individuals (papers I and II); (2) effect of inter-individual differences in behaviour on the relationship between individuals life-history traits and available resources (papers III and IV); (3) link between demo-genetic structure of population and growth and mortality rates of individuals (papers V, VI and VII). Datasets for this thesis were collected during a long-term mark-recapture study on wild brown trout population (2005-2011) in the catchment of the Otava River in Šumava National Park (Czech Republic) and a set of field and laboratory studies conducted on wild populations in streams on west coast of Sweden. In accordance with some previous studies, this thesis showed that growth of juvenile brown trout is negatively affected by population density. Nonetheless, this thesis reveals that the negative effect of density dependent..