Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) are an important economic, recreational, and ecological resource in the European Atlantic and Baltic seaboard, from northern Norway to Portugal. In economic terms, the worth of a single salmon and a single sea-trout has been assessed at €4273 and €593. The salmon and sea trout fishery on the River Spey alone contributes €13.5 million to household incomes annually. Eurasian beavers (Castor fiber), once largely extirpated in Europe, are now recolonising the salmon and sea trout range. Though beavers represent one of the major success stories of modern European conservation, their return to rivers holding economically and socially important salmon and sea trout resources is of concern because beaver dams can block fish movements, especially migrations to breeding grounds, and remove freshwater habitat. By altering the habitat use, survival, and growth of these fishes beavers may impact fish production. Although the potential for beavers to influence salmon and sea trout is very high, this phenomenon is largely unstudied in Europe leaving a knowledge gap for management of growing beaver populations. We propose to conduct a thorough study addressing this European scale knowledge gap based in Norway, through research and transfer of skills by an experienced N. American researcher which will create long-term collaborations. Norway is currently unique in having both an anadromous salmonid population of major economic and social importance, and a large Eurasian beaver population. The fellowship will bring a researcher at the forefront of her field (studying the impact of N. American beavers on Pacific salmon) to Europe, where many scientists will benefit from her knowledge of the field. This project is timely due to the continuing success of beaver recolonisation and extremely relevant due to the lack of data regarding the strong potential for beavers to impact important Atlantic salmon and sea trout fisheries.