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Antarctic blue whales (Balaenoptera musculus intermedia) are the largest and formerly most abundant blue whale subspecies, but were hunted to near extinction last century. Estimated whaling mortality was unsustainable from 1928 to 1972 (except during 1942–1944), depleting them from 239,000 (95% interval 202,000–311,000) to a low of 360 (150–840) in 1973. Obtaining statistical evidence for subsequent increases has proved difficult due to their scarcity. We fitted Bayesian models to three sighting series (1968–2001), constraining maximum rates of increase to 12% per annum. These models indicated that Antarctic blue whales are increasing at a mean rate of 7.3% per annum (1.4%–11.6%). Informative priors based on blue whale biology (4.3%, SD = 1.9%) and a Bayesian hierarchical meta‐analysis of increase rates in other blue whale populations (−3%, SD = 11.6%), suggest plausible increase rates are lower (although the latter has wide intervals), but a meta‐analysis of other mysticetes obtains similar rates of increase (6.7%, SD = 4.0%). Possible biases affecting the input abundance estimates are discussed. Although Antarctic blue whales appear to have been increasing since Sovier illegal whaling ended in 1972, they still need to be protected‐their estimated 1996 population size, 1,700 (860–2,900), was just 0.7% (0.3%–1.3%) of the pre‐exploitation level.

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To study whether or not wide-rang~ng pelagic predators should be affected by localized changes in prey availability, interannual variab~lity in body fat condition index (assessed from girth measurements) of minke whales Balaenoptera acutorostrata was analyzed in relation to their distribution, stomach-content mass and sea-ice extent during the austral summer in the Antarctic Ocean between 130°E and 170°W. The research area comprised offshore, ice-edge and Ross Sea areas. Of the 3 years (1990/91. 1992/93 and 1994/95) included in the study, 1994/95 was a year of significantly poor body fat condition compared with the other 2 years. The 1994/95 year was characterized by extensive sea-ice conditions, covering the usually krill-rich slope region throughout the season. Since minke whales were scarce and their stomach-content mass small in the ice-edge area during 1994/95, food availability in the area during the season was considered to be poor as a result of the high sea-ice extent. Antarctic krill Euphausja superba was regularly the dominant prey species throughout the survey area, although on the Ross Sea shelf E. crystallorophias was the codominant prey with E. superba. The spatial distribution of body size and maturity of E. superba Indicated apparent unsuitability of the Ross Sea area as a nursery and spawning ground for that species. The Ross Sea area was considered to be an area of low food supply throughout the study period, considering the lower level of stomach contents. Paradoxically, this area usually contained numerous minke whales, especially pregnant females. In conclusion, minke whales appear to have been affected by considerable interannual variability in food availability in the ice-edge area, i.e. potentially the most krill-rich area along their migratory route.