VANN: Spatial and temporal variation in production of juvenile Atlantic salmon: the importance of small streams as rearing habitats

Being able to identify the primary nursery habitats for juveniles in salmon populations is of prime importance for managers, especially as river systems are coming under pressure from anthropogenic disturbances. The smaller streams in river systems are es pecially vulnerable. Earlier studies from the subarctic Tana River system show that salmon parr migrate in large numbers into small streams in which no spawning occurs. These small streams can therefore be of great importance for the production of salmon. We will in this project choose three small streams (including historical data from these streams) in the Tana River system, and use a combination of traps, individually unique PIT tags, electrofishing, stable isotope tracing and manipulative experiments to get knowledge on parameters like growth, survival, energy budgets, migratory choice and production. As a part of this project, we will partake in an ongoing long-term project in West Brook (USA), in which the same methodology is used to study interacti ons between salmon, brown trout and brook trout. Models of competition parameters from West Brook will be applied to the data from Tana as a test. The Tana River system is still relatively undisturbed, so knowledge from this system will have important val ue for managers planning habitat restoration projects in other more anthropogenically disturbed systems. The study will include a post doc-project and cooperation with several national and international research institutes, including a half-year long rese arch stay in USA.