Spatially resolved past and projected changes of the suitable thermal habitat of North Sea cod (Gadus morhua) under climate change

Previous studies have identified changes in habitat temperature as a major factor leading to the geographical displacement of North Sea cod in the last decades. However, the degree to which thermal suitability is presently changing in different regions of the North Sea is still unclear, or if temperature alone (or together with fishery) is responsible for this displacement. In this study, the spatial distribution of different life stages of cod was modelled from 1967 to 2015. The model is fit point-to-point, spatially resolved at scales of 20 km. The results show that suitability has decreased south of 56°N (>12% in the Southern Bight) and increased north of it (with maximum of roughly 10% in southern Skagerrak). Future changes to suitability were estimated throughout the century using temperature projections from a regional climate model under the Intergovernmental Panel on Climate Change scenario RCP8.5. The results show that southern Skagerrak, the central and northern North Sea and the edge of the Norwegian trench will remain thermally suitable for North Sea cod throughout the century. This detailed geographical representation of thermally suitable key zones for North Sea cod under climate change is revealed for the first time through the improved resolution of this analysis.