Karen E. van de Wolfshaar

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.

The standard Dynamic Energy Budget (DEB) model provides a mechanistic framework for describing how organisms allocate energy to growth, maintenance, development, and reproduction. The DEB model has been widely applied across taxa and environmental contexts; however, under seasonal food limitation, the standard formulation may predict insufficient reserve mobilization to meet somatic maintenance. The options to meet somatic maintenance in such cases, namely paying from structural tissue, resulting in shrinkage of body size, or paying from reproductive material, are unrealistic for many species. To address this limitation, we propose a modified formulation, termed the DEB-Storage model, which introduces an additional energy storage compartment. This compartment provides an auxiliary energy pool that can be mobilized when reserves alone cannot meet maintenance demands, preventing unrealistic structural shrinkage and avoiding depletion of reproductive tissue. The advantages of DEB-Storage and the storage compartment was demonstrated using a fish species (Pleuronectes platessa) under realistic seasonal forcing of temperature and food availability. The results show that compared to the standard DEB model, the DEB-Storage formulation reproduces observed seasonal patterns in growth, reproduction, and body condition more accurately, providing a mechanistically consistent framework for modelling organisms in seasonal environments.

The ability to predict how fishes respond to changes in temperature and resource variability is paramount to developing sustainable management plans and for projecting the direct and indirect effects of climate change. We developed a versatile, physiological model capable of providing size-specific estimates of fish growth and fecundity across varying temperatures and resource levels. The model includes a mechanistic representation of individual-level life history processes across diverse biogeographic and functional fish guilds, using direct, species-specific parameter estimates. We demonstrate its application to five marine species (Atlantic cod, Atlantic herring, five-bearded rockling, European sprat and thinlip mullet), which differ in life history strategies and biogeographic distributions, but all rely on intertidal nursery habitats—areas particularly susceptible to anthropogenic change. In all simulations, resource availability had a stronger influence on fish performance than temperature. Nevertheless, the model also revealed how and why higher temperatures often decreased fitness and/or survival of specific types of species. We made no changes to the model structure for different species, and the resulting model predictions were not fitted but were based on eco-physiological first principles. Comparison between modelled and empirical data collected in the shallow Wadden Sea (southern North Sea) confirmed benefits of warming to thermophilic, range-expanding species, while core (established) species at their lower latitudinal limits of their distribution face local extirpation. The model allows insight into more variables than often reported from survey and monitoring efforts, such as reproductive output. The model’s broad applicability across a range of species, geographic regions and research objectives makes it valuable for generating knowledge needed to buttress actions aimed at addressing ecological and conservation challenges in a future climate.