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Among large cetaceans in the Southern Hemisphere, fin whales were the most heavily exploited in terms of numbers taken during the period of intense industrial whaling. Recent studies suggest that, whilst some humpback whale populations in the Southern Hemisphere appears to have almost completely recovered to their estimated pre-whaling abundance, much less is known about the status of Southern Hemisphere fin whales. Circumpolar estimates in the 1990s suggest an abundance of about 5500 animals south of 60° S, while the IDCR/SOWER-2000 survey for the Scotia Sea and Antarctic Peninsula areas estimated 4670 fin whales within this region in the year 2000. More recent studies in smaller regions indicate higher densities, suggesting that previous estimates are overly conservative and/or that fin whales are undergoing a substantial increase. Here we report findings from a recent multi-vessel single-platform sightings survey carried out as part of the 2019 Area 48 Survey for Antarctic krill. While fin whales were encountered throughout the entire survey area, which covered the majority of CCAMLR Management Area 48, they were particularly abundant around the South Orkney Islands and the eastern Bransfield Strait. Large feeding aggregations were also encountered within the central Scotia Sea between South Orkney Islands and South Georgia. Distance sampling analyses suggest an average fin whale density throughout the Scotia Sea of 0.0256 ( ) whales per km2, which agrees well with recent density estimates reported from smaller sub-regions within the Scotia Sea. Design-based distance sampling analyses resulted in an estimated total fin whale abundance of 53,873 (CV = 0.15, 95% CI 40,233–72,138), while a density surface model resulted in a slightly lower estimate of 50,837 (CV: 0.136, 95% CI 38,966–66,324). These estimates are at least an order of magnitude greater than the previous estimate from the same region based on the IDCR/SOWER-2000 data, suggesting that fin whales are und

Humpback whales (Megaptera novaeangliae) are showing strong recovery from commercial whaling in the western South Atlantic. In this region, humpback whales migrate annually from their winter breeding grounds off the coast of Brazil to their summer feeding grounds near to the Polar Front, an area that includes the waters of South Georgia and the South Sandwich Islands (SGSSI). This latter region includes a Marine Protected Area (MPA), which has been developed to ensure sustainable management of fisheries, and protection of foraging predators. To date, management measures within the MPA have primarily been concerned with foraging predators that rely upon Antarctic krill, including for a number of previously over-exploited species. This includes the regional humpback whale population now in recovery in the western South Atlantic. With humpback whales increasing, understanding their spatiotemporal distribution within the MPA is important as it will help inform management particularly in respect of interactions between humpback whales and the regional fishery for Antarctic krill. Here we develop habitat models from the distribution and movement patterns of 16 individuals at their high-latitude feeding grounds, south of 50°S. We show that whale habitat use varies throughout the foraging period. Upon reaching their feeding ground, whales use the area to the east of the South Sandwich Islands, moving westward into the centre of the Scotia Arc and towards South Georgia during the high summer, and then expanding back towards the east in the winter. Based on these findings, we discuss the implications for the future, including necessary research required for underpinning management.