Identifying core areas for mobile species in space and time: A case study of the demersal fish community in the North Sea

Identifying well suited sites for spatial conservation measures to protect mobile species is a challenging task. Intra- and interannual movements of individuals due to foraging, reproduction and environmental change make it difficult to identify the best placed locations. This study presents a generic approach for determining a species’ consistent core areas in space and time by using point abundance data from annual surveys. For this approach no statistical modelling is required and thereby it is well suited to obtain distribution maps for all surveyed species without knowledge on environmental predictors, thereby ignoring any issues related to data availability, quality and model confidence. Generating distribution maps for a suite of demersal fish species by using data from a scientific fisheries survey allowed to identify consistent core areas for 53 species in winter and summer over a period of 21 years (1998–2018). By overlaying single species’ distribution maps, hotspots of fish diversity could be compared to designated sites of marine protected areas (MPA) within the European Natura 2000 network. A majority of the identified diversity hotspots as well as the core areas of threatened and endangered species are currently not overlapping with the designated Natura 2000 MPAs. These MPAs might therefore not contribute sufficiently to the protection of marine demersal fish as an important component of marine ecosystems. Alternative spatial management options and tools implemented through other marine policies are needed to amend the Natura 2000 MPA network for the effective conservation of demersal fish in the North Sea.