Distributions of krill and Antarctic silverfish and correlations with environmental variables in the western Ross Sea, Antarctica

Antarctic krill Euphausia superba, crystal krill E. crystallorophias, and Antarctic silverfish Pleuragramma antarctica are key mid-trophic level species in the Ross Sea, connecting primary production to the upper trophic levels. Distributions of these species were constructed from observations made in the western Ross Sea from 1988 to 2004. Distributions of environmental conditions were obtained from a 5-km resolution circulation model (temperature, mixed layer depth, surface speed) and satellite-derived observations (chlorophyll, sea ice cover). A hierarchy of statistical methods determined correlations and relationships between species and environmental conditions. Each species occupies a localized habitat defined by different environmental characteristics. Antarctic krill are concentrated along the northwestern shelf break in a habitat characterized by deep (>1000 m) bottom depth, warm temperature (1 to 1.25 degrees C), decreased sea ice, and proximity to the shelf break. Crystal krill and Antarctic silverfish are concentrated in Terra Nova Bay. Common characteristics of the habitat for these species are southwesterly location, coastal proximity, and cold temperature (-1.75 to -2 degrees C). The habitat characteristics obtained for the 3 species provide a basis for projecting potential distribution changes in response to environmental change and for delineating regions of the Ross Sea for focused management and selection of marine protected areas that support ecosystem-level conservation plans.