The life cycle of the anadromous Atlantic salmon (Salmo salar) can span large geographic, political, and socio-economic boundaries. Management strategies and regulations that only concentrate on small spatial scales often overlook larger basin-wide problems, especially relating to post-Spawn seaward migration. In this master thesis one entire migration cycle of wild adult Atlantic salmon in the unregulated northern Swedish river Vindelälven was monitored by radio-telemetry tracking during upstream Spawning migration and downstream seaward migration back to the Baltic Sea. The effect of ladder passage variables (time to pass, total time in the ladder, passage day over the ladder) at a fish ladder downstream in the river Umeälven, as well as fish size, were evaluated to determine if differences in upstream migration distance in the river Vindelälven could be observed. Ladder passage variables did not affect migration distance, but size exhibited a negative relationship to migration distance.

During the migration season in 2013 a study on Spawning migrating salmon and the effect of water flow on the behavior was conducted of the salmon at the Forshaga hydropower station in the River Klarälven. The River Klarälven with its nine hydropower plants on the Swedish side, constituting migration obstacles for the migrating salmon. Fortum Generation AB has together with the County Administrative Board restored a salmon trap at the lowermost hydropower station in Forshaga, aiming at making it possible for the salmon to swim into the trap, and thereafter be transported by truck past the power plants and then continue their journey to the Spawning grounds on their own. Unfortunately, it is believed that the trap does not work as well as it should. In this study, I focused on salmon position in relation to water flow and if the number of salmon that swam into the fish trap differed between salmon with previous experience of the trap (experienced) and salmon without experience (unexperienced).

The classic view of trout (Salmo trutta) life history is that trout begins its life in freshwater, migrates to the ocean after about 1-4 years and then returns to freshwater to Spawn. As trout fry have been caught at the mouth of the River Emån, near the Baltic Sea, researchers have speculated that some trout emigrate during their first year of life. The purpose of this study was to describe the variation in the length of time trout reside in freshwater before they migrate to the ocean for the first time. Another purpose was to investigate whether it was possible to discern where and how long the fish spent in freshwater and saltwater during different parts of their lives. Between 2007 and 2009, 23 adult trout were captured in the River Emån in southeastern Sweden.

Sammanfattning I september 2008 fångades 311 juveniler (unga individer) av arten sill (Clupea harengus) in vid fyra olika områden på den svenska västkusten; Råssö, Hunnebo, Askerö- och Gullmarfjorden. Genetiska, kemiska och morfologiska data (längd och vikt) samlades in i syfte att bestämma vilka populationer de härstammade ifrån. Fångster av sill är så gott som alltid av blandat ursprung eftersom individer bara samlas i de populationer de stammar ifrån vid den tid på året då det är dags för parning (lek). I den här uppsatsen klassificerar jag juvenilerna till tre regioner i vilka populationerna ingår, genom att jämföra de data som samlats in från juvenilerna med motsvarande data i en stor databas över populationer i Nordsjön, Skagerrak, Kattegat och Östersjön samt med ytterligare en population, Risør, som inte ingår i denna databas. Data om populationerna kommer från samples och de sanna populationsparametrarna (dvs.