The distribution of skates (Order Rajiformes) along the Norwegian continental shelf and slope

Skates (Class Chondrichthyes, Order Rajiformes) are locally abundant in high latitude ecosystems that are experiencing rapid environmental change, increasing interests of primary industries, and changes in fishing activity. Effective management of these and other marine features depends on robust biological baselines from which ecological and demographic trends can be evaluated. Skates along the Norwegian continental shelf and slope, a biologically and commercially important region in the Nordic Seas, are severely underrepresented in the scientific literature compared to neighbouring seas. Despite being a regular feature of fisheries bycatch, skates are seldom identified to species in landings statistics, which impedes monitoring efforts. This has been attributed to issues of taxonomic confusion and the low commercial value of skates. Following recent taxonomic revisions within the Rajiformes and improved identification keys aboard research surveys, we evaluated the occurrence, geographic and size distributions of skates from 5005 demersal trawl hauls across the Norwegian continental shelf and slope (north of 62°N) in the period 2015–2024. The results were compared to existing literature from the surrounding seas. We confirm the occurrence of at least ten skate species in the region, half of which are threatened with extinction (IUCN Red-List). The skate fauna was dominated by the widely distributed Amblyraja radiata, A. hyperborea, Rajella fyllae, and Bathyraja spinicauda, for which all size classes were locally present. Their occurrence was modelled using generalized additive mixed models, which indicated species-specific but overlapping distributions in three-dimensional space. Six other species were occasionally caught (Rajella lintea, Dipturus oxyrinchus, D. nidarosiensis, Leucoraja circularis, Raja clavata, and Leucoraja fullonica). Rare catches of other members of the Dipturus, Leucoraja, and Raja genera could not be verified; however, D. intermedius has been confirmed from citizen science reports. The results fill an important knowledge gap concerning the skate community assemblage in the Norwegian Sea, highlighting its role as a transition zone between temperate (e.g. the North Sea) and Arctic community assemblages. The results can serve as a baseline to assess fisheries catches, habitat use, and future distribution and community shifts in this rapidly changing region.