Composition of population and transport of juveniles of Antarctic krill in Powell Basin region (northwestern Weddell Sea) in January 2020

Abstract

This paper presents the data on distribution and size composition of the Antarctic krill (Euphausia superba) population in the northwestern Weddell Sea (Powell Basin) and adjacent areas in summer 2020. Juvenile krill dominated in the western Powell basin and the eastern Bransfield Strait as a result of transport with the advected Weddell Sea water and drifting sea ice. Using a distribution mixture analysis made possible to identify up to 9–10 size groups of krill. Groups 1–4 corresponds to juveniles (average size about 22, 25, 27–28 and 32 mm respectively). They may reflect the transport of different “waves” of recruitment of the Atlantic sector krill population with the waters of the western branch of Weddell Gyre as well as the presence of juvenile krill of local origin. Groups 5–7 are intermediate in size (average length within 38–43 mm) and include mostly immature specimens. Larger groups 8–10 comprise of mostly mature females and mature and immature males. The maximum average size of the largest group reaches about 53 mm. the Wedell Front zone in the north of Powell Basin plays an in important role for retention and growth of krill, originating from different sources: western Weddell Sea, Bransfield Strait and the zone of the southern branch of Antarctic Circumpolar Current.