Interannual changes in body fat condition, stomach content mass and distribution of minke whales in Antarctic Areas IV and V

As an indicator of body fat condition, interannual variability in girth of minke whales (Balaenoptera acutorostrata) was analyzed in relation to sea-ice extent, stomach-content mass and distribution of minke whales in Antarctic Areas IV (70° -130° E) and V (130° E-170°W) from 1989/90 to 1994/95. Of the six years included in the study, two were categorized as years of poor body fat condition, and three as years of good condition. Estimated body weight gain during the feeding season in poor years was 25 % lower than in good years. The relationship between girth and stomach content mass in the ice-edge zone suggests that girth can be a useful indicator of food availability. In Areas IV and V, krill (Euphausia superba) was the dominant prey species, but in the southern part of the Ross Sea (in Area V), E. crystallorophias was the dominant prey species. Distribution of minke whales showed a greater interannual variability in Area V than in Area IV, reflecting a greater degree of variability in sea-ice extent in Area V. In Area V, in a year of high sea-ice extent, the krill-rich slope region in the western zone was covered by ice. This may have led to poor food availability and resulted in a very low density of minke whales along the ice-edger The Ross Sea zone was an area of low food supply throughout the study period. Paradoxically, this zone always contained numerous minke whales, especially pregnant females.