DISTRIBUTION OF ANTARCTIC KRILL CONCENTRATIONS EXPLOITED BY JAPANESE KRILL TRAWLERS AND MINKE WHALES (Eleventh Symposium on Polar Biology)

Based on Japanese krill fishing and minke whaling data, the distribution of Antarctic krill (Euphausia superbd) concentrations was investigated in relation to bottom topography, sea-ice and hydrographic features. Data were from the Indian, Pacific and western Atlantic sectors. In early summer (December) high density concentrations of krill frequently occurred in the vicinity of southerly positioned pack-ice edges and in the embayments surrounded by the pack-ice edge. In mid and late summer (January-March) when the ice-edge was at its southern-most limit, krill fishing data indicated that harvestable areas were associated with the continental and insular shelf breaks, not with the pack-ice edge. Minke whaling data also suggested that not only sea-ice but also topographical features such as the continental shelf breaks and banks may be important factors affecting minke whale (Balaenoptera acutorostratci) distribution. Krill harvesting areas in the vicinity of the shelf breaks were often coincident with hydrographic fronts. These results suggested that hydrographic features caused by uneven bottom topography (e. g. shelf breaks or banks) may induce the formation of krill concentrations in mid and late summer. The extremely high concentration of minke whales and their food composition suggested the high abundance of E. superba around a bank on the Ross Sea shelf.