Antarctic krill have a circumpolar distribution, but the highest densities are found in the Atlantic sector of the Southern Ocean in the areas around and to the North-east of the Antarctic Peninsula. This seems to be a preferable area due to the strong phytoplankton blooms in summer and the extensive ice cover in winter providing food from ice algae. Moreover, the ice cover provides protection and food for the fry and is therefore a significant factor for the survival in the early phases of life. The high concentrations of Antarctic krill in the Atlantic sector suggest that they have mechanisms to maintain their distribution in this area withstanding the forces of the circumpolar current. Most of the krill is found in the open water masses in swarms with densities reaching as high as 20000-30000 individuals m-3.
Antarctic krill is the main focus organism for the IMR research activity in the Southern Ocean, and aspects that are investigated include acoustic properties related to acoustic biomass estimation, distribution, demography, swarm characteristics and interactions with predators and prey.