Abstract
A dense aggregation of krill Euphausia superba in the region of Prydz Bay, Antarctica, was investigated in March 1987 using hydroacoustic and net sampling techniques. Maximum aggregation density was estimated to be 1530 g m-3; total biomass 57000 tonnes wet weight. This is the first reported observation of an aggregation of this magnitude in the Pyrdz Bay region. The aggregation is also unique in that it consisted mainly of very large sexually immature males, the majority 48 to 58 mm in body length.