During the timber floating era, most of Sweden?s watercourses were altered. This decreased the amount of available spawning habitats for salmonids, and hence had a negative effect on the riverine brown trout (Salmo trutta) populations. Reconstruction of spawning grounds is today a common measure in restoration of altered streams in Sweden. However, very little evaluation of the effectiveness of these reconstructed spawning grounds exists.

The population of seatrout and salmon are threatened by over-fishing in the sea and loss of spawning and growing habitats caused by logging activities in many swedish rivers. The knowledge of the spawning migration and the habitat use of the seatrouts and salmon are limited. This study analyse the upstream spawning migration of Atlantic salmon and sea-running brown trouts from the lower part of the rivers to their spawning sites in the rivers Vindelälven and Piteälven. A knowledge about the distribution of spawning sites in the rivers will help these fish population in future restoration programs. In the fishladder at Norrfors in the river Umeälven were 29 sea trout and 20 salmon radio tagged and subsequently released and followed during their spawning migration upstream Vindelälven. They were tracked on their position in the river once a week.

Timber floating operations in Scandinavia during the 19th and 20th centuries has contributed to severe negative impacts on riverine ecosystems. Increase in water velocity and lack of stream bed heterogeneity as a result of stream channelization lead to increased bed load transport. Since availability and recruitment of new suitable spawning substrate in Scandinavian watercourses is sparse, spawning habitats for salmonids has become a scarce commodity. Lately, increasingly more attention has been given to the recreation and improvement of brown trout (Salmo trutta) spawning habitats in restoration projects. While much of the research on spawning habitat has been focused on evaluation of the influence that the constructed spawning grounds have on fish populations, few studies have been conducted to evaluate the persistence of these constructions over time. I evaluate erosion of constructed Spawning beds as an effect of sediment transport attributable to water discharge.

In many regulated rivers, authorities have stocked hatchery salmon to compensate for loss of wild populations. However, hatchery fish have not always behaved as wild fish do, and stocking them has not always fully compensated for the loss of wild fish. The purpose of this study was to compare swimming behaviour in the river before spawning, the choice of spawning areas and body size between wild and hatchery-reared salmon in the river Klarälven. Salmon behaviour in the river before spawning was analyzed using radio telemetry. The salmon were caught at Forshaga power plant, radio-tagged and returned to Klarälven at Ekshärad, 107 km from the river?s mouth.

In this study the spawning migration activity, habitat choice (depth and temperature), foraging activity, duration of stay in the spawning site and homing-behavior was studied for anadromous pike (Esox lucius) in the wetland Österby myr, Gotland.The spawning migration was concentrated to dusk and dawn, a homing behavior was confirmed and there was no significant difference between sexes with respect to duration of stay. A difference in habitat choice and small variation in foraging activity between individuals was established..

There are several thousands shallow bays along the Swedish east coast. Most of them are disturbed by different human activities, and undisturbed bays can be considered as quite unique. In the sheltered shallow bays water warms up more rapidly than adjacent water favoring the growth of vegetation, which in turns is beneficial to spring spawning fish species like perch and pike. It is nowadays more common that coastal habitats are inventoried to facilitate future preservation and planning. The aim of this study was to investigate the shallow bay Utanåfladen (59° 53`31.38 N 19°00`44.90 E) in the north Stockholm archipelago and evaluate its habitat value.

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 last two hundred years many wetlands and streams in Sweden have been lowered to provide land for agriculture and forestry. Some of the coastal wetlands and streams probably served as spawning sites for certain species of fish in the Baltic Sea, but the present situation is not well known. As standardized methods to monitor fish in running waters are carried out during late summer or autumn, there is a need for methods to sample spring-spawning fish in these streams.The aim of this study was to survey the lower kilometer stretch of Hammerstaån in Stockholm, to investigate the extent to which the stream is used by spring-spawning fish. Furthermore, the study aims to evaluate a new type of survey fishing gill net called strömöversiktsnät (SÖN). This was done by comparing the catch of fish by SÖN with that of fyke nets.

During the last two hundred years many wetlands and streams in Sweden have been lowered to provide land for agriculture and forestry. Some of the coastal wetlands and streams probably served as spawning sites for certain species of fish in the Baltic Sea, but the present situation is not well known. As standardized methods to monitor fish in running waters are carried out during late summer or autumn, there is a need for methods to sample spring-spawning fish in these streams.The aim of this study was to survey the lower kilometer stretch of Hammerstaån in Stockholm, to investigate the extent to which the stream is used by spring-spawning fish. Furthermore, the study aims to evaluate a new type of survey fishing gill net calledströmöversiktsnät (SÖN). This was done by comparing the catch of fish by SÖN with that of fyke nets.

Habitat selection of migratory brown trout at the upper reaches of River Vindelälven, wasstudied in September during the pre-spawning period. The fish migrate from down- orupriver lakes for spawning in the river and data was collected by habitat mapping andradio-telemetry. Habitat selection of fish was analysed with preference curves andstatistical modelling, using the physical variables; depth, stream velocity and streambedsubstrate. Preference curves were derived by comparing fish habitat use with their nearbyavailable environment while the statistical modelling aimed to answer three main questions.1) Do the trout have a specific preference of depth, water velocity and streambed substrate?2) Is there any difference in habitat selection between sexes? 3) Is there a shift in habitatselection over time? The preference curves indicated that trout favored water depths of 1-2m, velocity compositions characterized as glides (c.

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).

Many watersheds have lost stocks of migrating fish species because of the development of hydroelectric plants and other fragmenting barriers. The remaining stocks of migrating Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in River Klarälven, Sweden are five times smaller compared to one hundred years ago. A fish-trap at the hydroelectric plant in Forshaga has been vital for the continued existence of the stocks. This is the first hydroelectric plant of eight, blocking the way to the spawning grounds. Spawners are collected in the trap for both hatchery and transport by truck upstream and past seven more hydroelectric plants to the spawning grounds, where they are released for possible natural reproduction.

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.

I have done a follow up study of the restoration of two rivers, Röälven and Grundan, in order to evaluate the effects of the restoration on the endemic population of trout. Both rivers have been used for timber floating during many years throughout the 20th century, and because of this, had all obstacles such as rocks and wood parts removed. In 2004-2005 both rivers were restored, and rocks and wood were put back into the rivers. Spawning grounds were created and boulder dams were constructed to promote the streaming water. The result showed that the trout population of both rivers increased after the restoration, but also that the trout population of Röälven increased more than that of Grundan.

Ammerån which is a small forest river in eastern Jämtland is a well-known river that has been a popular fishing river for a long time. The actual Ammerån begins downstream the lake Solbergsvattnet at Hammerdal and flows into the Indalsälven 10 km upstream Hammarstrand. The river environment switches between forests with wilderness feeling and open agricultural land. The entire Ammerån is today a nature reserve and protected from hydropower development. Fishing in Ammerån has mainly been focused on trout and grayling, and is so even today.