Several countries have recently shown an interest in commercial krill fishing. An understanding of krill population structure is needed to establish sound management of krill fisheries. A short review is undertaken of recent studies in genetic and morphophysiological variability of krill and Antarctic water circulation. On the basis of the review, it is suggested that there is probably one composite population of E. superba in the Southern Ocean subdivided into several independent sub-populations. The number of these sub-populations is expected to correspond with the number of quasi-stationary cyclonic water circulations. At present, at least six stable cyclonic water circulations can be found and at least two or three of them may be habitats of independent krill sub-populations. A proposal is given for future studies into krill population structure.