During the survey of Subarea 48.4 from 17 January to 1 February 2000 it was observed that krill was present in non-aggregated and scattered forms, as well as in swarms. Differences between spatial distribution patterns of different krill aggregation forms in relation to water mass structure and dynamics were revealed.

Distributional features and physical characteristics of some 2 400 krill swarms detected in the study area were sized acoustically and are described in this paper. Results of comparisons of swarm parameters by area and season are given.

The effect of spatial distribution patterns of krill aggregations on the horizontal and vertical distribution of krill biomass is shown. About 64% of the krill biomass was concentrated in krill swarms in the upper 80 m depth layer within meander and eddy zones of the Weddell Sea (14% of the study area).

Spatial distribution patterns of krill aggregations and distribution of krill biomass density were analysed with a view to detecting potential fishing grounds where the recommended precautionary catch limit could be taken. Such fishing grounds could be located within the zones in which swarms were concentrated and where the biomass density was greater than 1.5 g m^-3. The biomass in these potential fishing grounds amounted to about 1.7 million tonnes. It was shown that the removal of biomass up to a recommended precautionary limit could be possible from such grounds despite a predicted low catch per hour of trawling.