Future climate change and fisheries reorganize a high Arctic food-web toward benthic and invertebrate dominance

High-latitude marine ecosystems are particularly exposed to climate change, which transforms habitats and reshapes biological communities. Atlantic generalist consumers are expected to profit from extended ranges of suitable environments and novel trophic interactions, whereas Arctic specialist species are often confronted with habitat loss. Additionally, growing fish stocks may increase the likelihood of industrial fisheries, thereby triggering changes that alter community composition. Here, we employ topological network analysis and dynamic modeling to explore the impacts of climate change and fisheries on the Kongsfjorden, an Arctic fjord ecosystem. We find that the decline of Polar cod (Boreogadus saida), an Arctic endemic species threatened by habitat (sea-ice) loss through warming, indirectly increases the trophic pressure on high trophic-level fishes, piscivore seabirds, and marine mammals, and leads to decreased habitat connectivity. An increase in Atlantic cod (Gadus morhua) can partially mitigate the ecological impact on high trophic-level consumers. However, by lengthening food chains, it lowers trophic-transfer efficiency and limits the energy available for piscivore birds. The decline of both cod species, driven by the concomitant action of ocean warming and over-fishing, reduces functional network integrity. It further disrupts the connectivity between benthic and pelagic food webs, thus increasing the vulnerability of pelagic top predators. Our results highlight the importance of adopting a holistic perspective when exploring the indirect impacts of multiple anthropogenic stressors. They indicate that fishing in the Arctic can profoundly modify ecosystem structure, often amplifying the negative consequences of borealization. This work identifies the parts of the Kongsfjorden community that are particularly vulnerable to emerging pressures, providing stakeholders with guidance on conservation priorities.