IMIS

Conflicts between nature conservation and anthropogenic interactions like urbanization, aquaculture, fisheries and recreation in coastal marine ecosystems are common and divisive for communities. In Europe, the increasing use of near-coastal areas for sea cage aquaculture may negatively influence anadromous brown trout (Salmo trutta; a.k.a. sea trout) and Atlantic Salmon (Salmo salar). Salmonids provide important social and ecosystem services in many countries, including Norway. However, during the last 10-20 years, the abundance of both Atlantic salmon and sea trout have declined markedly in many regions. Knowledge about the biology, ecology and habitat use of salmonids is limited and insufficient for successfully planning sustainable coastal developments. "The secret life of sea trout" research program is using acoustic telemetry linked with physiology, stable isotopes and genomics to document marine migrations and habitat use of anadromous brown trout, Atlantic salmon and Arctic charr from several Norwegian fjords. The findings show that sea trout exhibits diverse marine behavior in time and space depending on nutritional state, sex and morphology of the home watercourse. Thus, potential negative impacts from coastal developments may vary among individuals and watercourses. Acoustic telemetry has been used in several estuaries and fjord systems in Norway to document potential conflicts with human influences such as different infrastructure and fish farming. At the same time, habitat use of sea trout has been studied in undisturbed and pristine estuaries at Kerguelen Island to serve as a reference. Results show that estuaries are important transition zones, especially for younger individuals, between the nursery areas in freshwater and feeding grounds at sea. Additionally, during certain times of the year, estuaries may act as an important longer-term habitat, with fish residing there for weeks to months, and sometimes for the whole duration of the summer feeding migration. A consequence of longer-term residency in estuaries is an increased risk of disturbance from boat traffic, industrial development, harbours, local pollution, gravel extraction, and other physical developments that are often located in estuaries.The findings from the projects are used by stakeholders when decisions are made regarding locations of new fish farms and development of infrastructure in coastal areas. The participation of the public in the research project through community consultations has provided educational opportunities for the local communities, especially their youth, and has allowed for exchange of local and scientific knowledge, enriching both communities. The aim of the Beiarfjord project is to further investigate the migratory behaviour of brown trout and Atlantic salmon in a northern fjord system, where the inner part is a marine protected area, while open sea cage fish farming is located in the outer part of the fjord complex.