Antarctic krill under perennial sea ice in the western Weddell Sea

The results of underwater observations and sampling of krill (Euphausia superba) in the western Weddell Sea during the joint Russian-USA Ice Station Weddell-1 Expedition (11 February-9 June 1992) are presented. Krill was sampled from the same large ice flee composed of both 1- and 2-year ice as it drifted northward for a distance of c. 700 km. Abundance estimates for krill under this flee were in the range 0.1-6.25 ind m(-2). Krill aggregate in areas where rafting of ice floes and formation of new ice occur, or around a protected diving hole. The krill sampled consisted mainly of furcilia 6 and post-larvae which did not belong to the 0+ group originating in this (1991-92) year, but presumably hatched in the summer season of 1990-91 and developed very slowly so that at the end of the following summer season, larval stages were still present in the population. No increase of the mean krill size was observed during 2.5 months of observation. The role of larval advection for the maintenance of krill population in the Weddell Sea is discussed.