Drivers of marine groundfish community composition in shallow- and deep-water subarctic habitats

Species distribution modelling is a widely used approach for studying species’ environmental niches and identifying the main drivers of species distribution. These modelling frameworks have been gaining popularity owing to the growing need among conservation ecologists and nature managers to understand and anticipate the distribution shifts accompanying ongoing environmental changes. To investigate the drivers of marine groundfish community composition in the subarctic, a joint species distribution model (JSDM) was applied to fish community data from the continental shelf and slope of Iceland. In a novel approach, the JSDM was used to compare the ecological niches of demersal and benthopelagic species with the niches of bathydemersal species. Depth and sea bottom temperature resulted as strong predictors of species distribution, with depth being more important for shallow-water species and temperature for deep-water species. Salinity, sea bottom slope, time at trawling, chlorophyll a concentration, and fishing intensity each explained ≤4% of the variance in distribution. Strong residual species’ co-occurrence patterns indicated the presence of additional spatially-structured processes that influence the distribution of marine fish in the area. Evidence for trait-environment relationships between sea bottom slope and three biological traits – age of maturity, growth coefficient, and aspect ratio of the caudal fin – are also discussed. This model, one of the first applications of a JSDM in subpolar seas, indicates a great susceptibility of subarctic and deep-water fish communities to changes in climate.