Climate change and spatial management reshape ecological and economic outcomes in North Sea fisheries

Abstract Climate change is reshaping marine ecosystems by altering primary productivity, shifting species distributions, and modifying ecosystem structure, adding a layer of complexity to spatial management. In parallel, the establishment of Marine Protected Areas (MPAs) and the rapid expansion of offshore wind farms (OWFs) are transforming the spatial footprint of human activities across the seascape. Together, these environmental and spatial drivers are changing ecosystem dynamics and fishing opportunities, with potential consequences for both ecological integrity and socio-economic viability. However, most approaches address these dimensions in isolation, underscoring the need for integrated modelling frameworks that can evaluate their combined and interacting effects. This study applies the North Sea Object-oriented Simulator of Marine ecOSystEms (OSMOSE) model to assess how climate change and spatial management shape ecosystem structure and function. The model represents trophic interactions and population dynamics of 14 ecologically and commercially important fish species, supporting scenario-based evaluations within an Ecosystem-Based Fisheries Management (EBFM) framework. Climate impacts are represented as bottom-up changes in productivity, economic drivers through projections of fish and fuel prices and efficiency, and spatial closures as top-down shifts in fishing effort. Across scenarios, climate change alone was found to reduce higher trophic level biomass by approximately 7%, with some variability across species groups. Climate impacts were also found to drive declines in proportion mature and typical length indicators for most species groups. Impacts of spatial effort displacement in combination with climate scenarios were comparatively subtle relative to the effects of climate alone, but revealed localized biomass gains inside closed areas, particularly inside the large Dogger Bank MPA, indicating potential sheltering effects. Effort reduction, in contrast, amplified both ecological and economic shifts, showing the largest changes in biomass composition relative to climate impacts alone, increases in maturity indicators, and improved value per unit effort for some metiers despite overall biomass losses. This work underscores the importance of adaptive, ecosystem-informed approaches that integrate both ecological and socio-economic dimensions to ensure a holistic evaluation of marine ecosystems under future environmental and management conditions.