Distribution, feeding and growth of hatchery-reared atlantic salmon (Salmo salar L.) parr stocked into rivers with various abiotic conditions

Within the research of efficiency of Atlantic salmon the artificial reproduction, feeding rate, distribution and growth of farm-raised one-year-old Atlantic salmon have been examined. The fish has been released into nursery areas with different hydrological characteristics located in the Rivers Kola, Umba, Srednyaya and Akkim in the Murmansk region. The observations have being conducted for 1-5 months since the moment of fish release. In natural habitat, juveniles rapidly distribute downstream and upstream regardless of water temperature, depth and current velocity. In all examined nursery areas adapting one-year-old juveniles prefer to stay at weak current sites close to the shore, hiding in the gravel. In all the cases farmed parr shows high feed rate, but qualitative composition of their food differs significantly from food composition of wild juveniles. Revealed peculiarities of adapting parr's distribution and qualitative food composition indicate the impact of long-term rearing at hatcheries on fish behavior. Growth rate of one-year-old juveniles is arcwise connected with fraction composition of gravel and the level of bottom fouling: the bigger bottom rocks are and the thicker the fouling is, the more intensive fish growth is. The revealed correlations have been described with equations of linear regression. Connections between juvenile growth and water temperature, current velocity and depth of the area have not been detected. The research outcomes could provide a basis for scientific advice for planning release sites and number of released one-year-old Atlantic salmon by hatcheries in the Murmansk region.