Biogeographic Changes in a High Latitude Marine Fish Community: Short‐Time Reversals in Response to Climate Variation

ABSTRACT Aim Determine whether changes in fish biogeographic composition and key facets of biodiversity are reversible at short time scales in a high latitude marine ecosystem experiencing ocean warming in the context of a recent short‐term cooling, and an increasing then declining dominant apex predator population. Location Barents Sea. Methods Survey data from an 18‐year time series of demersal fish communities, delineated as Arctic, Arctic‐boreal and boreal assemblages, was used to examine temporal changes in (i) biogeographic composition across the Barents Sea, (ii) taxonomic, functional and phylogenetic (alpha) diversity at a sub‐regional scale and relationships to abiotic and biotic drivers, and (iii) beta diversity at regional and sub‐regional scales. Results Community composition changes across the Barents Sea that were attributed to ocean warming showed signs of a reversal during short‐term cooling. At a sub‐regional scale, several biodiversity measures showed a reversal of changes in the north‐east, but different biodiversity measures as well as abiotic and biotic drivers revealed distinct patterns and trends. Species richness of the Arctic‐boreal group increased but then declined in the north‐east, while species richness of the Arctic group showed a persistent decline. Main Conclusions Our approach of dividing the Barents Sea into sub‐regions and different biogeographical groups revealed patterns that were different from those observed at a large spatial scale and for whole communities. The Barents Sea is heterogeneous regarding temporal changes in diversity, and the recovery potential of fish communities varies among biogeographical groups. Such heterogeneity needs to be accounted for in future conservation strategies and ecosystem‐based management.