Dispersion and abundance of Antarctic krill in the vicinity of Elephant Island in the 1992 austral summer

Antarctic krill Euphausia superba distribution and abundance were estimated from 4 acoustic surveys conducted in the vicinity of Elephant Island, Antarctica, from mid-January to mid-March 1992. The first and last surveys covered a 105 by 105 n mile study area centered on Elephant Island; the second and third surveys covered a 60 by 35 n mile area immediately north of Elephant Island. During the first survey, krill were distributed in a wide band extending along the north side of Elephant Island and wrapping around the western end; biomass was estimated to be 2.2 million metric tons (t). During the second survey, the highest densities of krill were over the shelf extending to the northwest from Elephant Island and including the Seal Island archipelago; high densities of krill also extended off the shelf from the northeast end of Elephant Island into deeper water. Biomass in the smaller survey area was estimated to be 0.7 million t. Three weeks later, high krill densities were still apparent in the vicinity of Seal Island, but the area of high density previously mapped off the northeast end of Elephant Island had diminished considerably; biomass was estimated to be 0.4 million t. During the final survey, conducted 6 wk after the first survey, krill were mapped in reduced densities primarily to the west of Elephant Island; biomass over the larger survey area had declined to 1.1 million t.