Euphausia superba and E. crystallorophias were the dominant species in the area studied, Thysanoessa macrura, E. jrigida and E. triacantha were also present. The abundance of krill was changing during the year; minimum occurred between March and August and maxima between December and February and from September till November. Age structure of three most frequently occurring species showed seasonal variations. The periods of development and Reproduction were different for T. macrura, E. erystallorophias and E. superba.

The distribution and some aspects of the ecology of Euphausia crystallorophias, Euphausia frigida, Euphausia triacantha and Thysanoessa macrura are presented. The investigations in the Polish Sector "A" show that E. triacantha is the northernmost and E. crystallorophias the southernmost species. These two species occurred least frequently. T. macrura was the most numerous and most regularly distributed species in the region under investigations.

In the investigated area, mass occurence of krill was observed in the vicinity of islands and the Antarctic Peninsula, in the waters above the shelf and shelfs slope. Small quantities of krill were found in the open oceanic waters. Immature individuals dominated close to the Antarctic Peninsula. Large, sexually mature kril dominated farther from the continent. Gravid females contributed little to the total populations. Krill of the largest size occured near the Palmer's Archipelago, and of the smallest size at the Antarctic Peninsula and the Elephant Island. It is likely that krill observed west and north of the Palmer Archipelago had been brought by currents from the Bellingshausen Sea. Krill in the Bransfield Strait originated probably from the mixing of populations carried by currents from the Weddell Sea and the Bellingshausen Sea.