Benthos plays a significant role as substrate, refuge from predation and food for a wide variety of fish and invertebrates of all life stages and should therefore be considered in the ecosystem approach (EA) to management. Epibenthos from trawl catches, used in annual assessments of commercial fish stocks, was identified and measured on-board. The 2011 dataset present the baseline mapping for monitoring and included 354 taxa (218 to species level) analysed with multivariate statistical methods. This revealed four main megafaunal regions: southwestern (SW), banks/slopes in southeast and west (SEW), northwestern (NW), and northeastern (NE) which were significantly related to depth, temperature, salinity, and number of ice-days. The SW region was dominated by filter-feeders (sponges) in the inflow area of warm Atlantic water while the deeper trenches had a detritivorous fauna (echinoderms). In the SEW region, predators (sea stars, anemones and snow crabs) prevailed together with filtrating species (sea cucumber and bivalves) within a mosaic of banks and slopes. Plankton-feeding brittlestars were common in the NW and NE region, but with increasing snow crab population in NE. Climate change, potentially expanding trawling activity, and increasing snow and king crab populations might all have impacts on the benthos. Benthos should therefore be a part of an integrated assessment of a changing sea, and national agencies might consider adding benthic taxonomic expertise on-board scientific research vessels to identify the invertebrate “by-catch” as part of routine trawl surveys.
Biogeographical patterns have an ecological basis, but few empirical studies possess the necessary scale and resolution relevant for investigation. The Barents Sea shelf provides an ideal study area, as it is a transition area between Atlantic and Arctic regions, and is sampled by a comprehensive survey of all major functional groups. We studied spatial variation in species composition of demersal fish and benthos to elucidate how fish and benthos communities co-varied in relation to environmental variables. We applied co-correspondence analysis on presence-absence data of 64 fishes and 302 benthos taxa from 329 bottom trawl hauls taken at the Barents Sea ecosystem survey in August-September 2011. We found highly significant similarities in the spatial pattern of distribution of benthos and fishes, despite their differences in motility and other ecological traits. The first common ordination axis separated boreal species in the south-west (Atlantic temperate water) from Arctic species in the north-east (Arctic cold water, ice-covered in winter). The second common axis separated shallow bank species from species found in deep basins and trenches. Our results show that fish and benthos communities had a similar relationship to the environmental gradients at the scale of hundreds to thousands of kilometres. We further discussed how fish-benthos interactions vary between sub-regions in the Barents Sea based on species traits and a food web topology for the Barents Sea. This study forms a basis for further investigations on links between fish and benthos communities in the Barents Sea.
Knowledge of the distribution of seabed sediments, benthic communities and their associated environment (biotopes) provides important baseline information for sustainable management of the oceans. The Barents Sea comprises a vast area of continental shelf spanning international boundaries, where this type of information is in increasing demand for management related issues in these high-latitude waters. Synthesis of existing data originally obtained for other purposes can provide an important first step in making the required information available, as well as helping to identify areas where further mapping should be prioritised. We present two related regional-scale maps recently generated for a large part of the Barents Sea continental shelf where varying amounts of existing data were available from Norwegian and Russian institutions: (1) a map showing the distribution of seabed surface sediments (1:3,000,000), and (2) a map showing the predicted distribution of benthic biotopes (4 km raster resolution) based on Random Forest modelling. The biotope map makes use of the sediment map as a key predictor variable, together with bathymetric, oceanographic and other environmental variables. Biotope classes are based on species composition as identified from benthic trawl samples. Compilation and synthesis of geo-referenced data from various sources can produce valuable results but can also lead to uncertainties in the resultant map products which are important to convey to data users. To support our thematic maps we present a confidence assessment of the foundation datasets contributing to the sediment map. We also discuss further issues related to map confidence and scope for updating the maps as new data become available.
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