Northern coastal ecosystems are experiencing environmental perturbations due to changing climate and human activities like harvesting and aquaculture. The project is aimed to investigate ecosystem structure and dynamics using ecosystem models (Ecopath wit h Ecosim) that integrate data from classical sampling methods and stable isotope data. The project will attempt to answer if it is possible to advocate exploitation and management regimes that enhance fishery yield, resilience, resistance and biodiversity in coastal ecosystems. Ecopath models will be parameterized for a fjord system, the Ullsfjord system at 70oN in northern Norway, based on data that will be collected in 2009 and data that were collected during the period 1993-96. The project has a compar ative approach with a local (comparison between the fjord ecosystems Ullsfjord and Sørfjord, and between time periods), regional (comparison of Ullsfjord/Sørfjord and Porsanger ecosystems) and intercontinental dimension (comparison of Norwegian and Canadi an northern coastal ecosystems). The model output will be compared to fishermens knowledge with regard to spatial and temporal variability in coastal ecosystems.