Scott Islands and Iselin Bank IMMA
Size in Square Kilometres
765,120 km2
Qualifying Species and Criteria
Humpback whale – Megaptera novaeangliae
Criterion C (2)
Antarctic Blue whale – Balaenoptera musculus intermedia
Criterion A; C (2)
Fin whale – Balaenoptera physalus
Criterion A
Antarctic minke whale – Balaenoptera bonaerensis
Criterion C (2)
Marine Mammal Diversity
Criterion D (2)
Lobodon carcinophaga, Globicephala melas edwardii, Hydrurga leptonyx,
Mirounga leonina, Orcinus orca, Balaenoptera acutorostrata
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Summary
The Scott Islands IMMA includes Scott Island, Balleny Island and the Iselin Bank. Situated at the northern end of the Ross Sea, they are far enough from the Antarctic mainland to be directly in the path of circumpolar ocean currents. Consequently, they create an upwelling of nutrient-rich deep water to the surface, which then generates high levels of biological productivity. This rich marine ecosystem serves as an important feeding area for humpback whales (Megaptera novaeangliae) and a hot spot for Critically Endangered Antarctic blue whales (Balaenoptera musculus intermedia) and Antarctic minke whales (Balaenoptera bonaerensis). The IMMA is used by many other species of marine mammals such as killer whales (Orcinus orca – both Type C and Type B1); Vulnerable fin whales (Balaenoptera physalus); southern long-finned pilot whales (Globicephala melas edwardii), southern elephant seals (Mirounga leonina), crabeater seals (Lobodon carcinophaga) and leopard seals (Hydrurga leptonyx).
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
Blue whales, Balaenoptera musculus, were hunted for over a century and whaling brought them to the brink of extinction before the species became protected by international agreement in 1966. The subspecies is red-listed as Critically Endangered (Cooke, J.G. 2018) and is of global interest as one of the most at risk baleen whale species in the Southern Ocean. The Antarctic form B. m. intermedia, which used to be the most abundant form of blue whale, occurs in the Antarctic in summer, from the Antarctic Polar Front up to and into the ice (Branch et al. 2006), including (in the past) the South Georgia area. Its winter distribution is poorly known, but the presumption has been that animals migrate in winter to lower latitudes, largely because blue whales were caught off Namibia, South Africa, in winter (Best 1998, Mackintosh 1965). Commercially exploited to critical population levels, the fin whale, Balaenoptera physalus, is currently a vulnerable species in the Southern Ocean (Reilly et al. 2013). Fin whales have a nearly circumpolar distribution in the Southern Ocean (De Broyer et al. 2014) with numerous records around the Balleny Islands (Naganobu et al. 2005).
Criterion C: Key Life Cycle Activities
Sub-criterion C2: Feeding Areas
This area has been identified as an important feeding area for humpback whales (Andrews Goff et al. 2018). Found in oceans and seas around the world, humpback whales typically migrate up to 25,000 km each year. Most populations feed in high-latitude waters, and migrate to tropical or subtropical waters to breed and give birth, fasting and living off their fat reserves. Their diet consists mostly of krill and small fish and their foraging habitat in the Scott Islands region is associated with the marginal ice zone (Andrews Goff et al.2018). This area has also been identified as an important feeding area, using passive acoustics, for Antarctic blue whales (Double et al. 2015, Miller et al., 2015). In addition, Antarctic minke whales are known to occur from around 7ºS to the ice edge (and into the ice fields) during the austral summer in the region where they feed mainly on krill (Ballard et al., 2012).
Criterion D: Special Attributes
Sub-criterion D2: Diversity
There is good tracking data to show that humpback whales use the area for feeding (Andrews Goff et al. 2018). This is also the case for some southern elephant seals (Hindell et al. 2017). Transect survey data show that this productive area is used by many species of marine mammals, including: Antarctic blue whales (Tangaroa Census of Antarctic Marine Life); minke whales (probably mainly B. bonaerensis but possibly also B. acutorostrata) (Tangaroa Census of Antarctic Marine Life); killer whales, Orcinus orca, (Tangaroa Census of Antarctic Marine Life); fin whales, Balaenoptera physalus, (Tangaroa Census of Antarctic Marine Life); southern long-finned pilot whales, Globicephala melas edwardii, and leopard seals, Hydrurga leptonyx. Satellite studies conducted in both McMurdo Sound and Terra Nova Bay show areas along the western Ross Sea coastline where Type-C killer whales engage in feeding activities and long-distance travel beyond the coast, outside the polar front (Eisert et al., 2015). The Type-B1 killer whale whales, which mammal-feed on mammals and birds that commonly occurs along the ice shelf in this region during the austral summer, taking advantage of both the seal and Adelie penguin colonies in the area (Andrews et al., 2008; Lauriano et al., 2007a,b). Antarctic minke whales are known to occur from around 7ºS to the ice edge (and into the ice fields) during the austral summer in the region. They feed mainly on krill and, in turn, are important prey for killer whales. High densities of Antarctic minke whales are recorded in the entire Ross Sea area (Ballard et al., 2012). The distribution of crabeater seals is tied to seasonal fluctuations of the pack ice. They can be found right up to the coast and ice shelves of Antarctica, as far south as the Bay of Whales, during late summer ice break-up. They occur in greatest numbers in the seasonally shifting pack ice surrounding the Antarctic continent (Hückstädt, L. 2015). Van Dam & Kooyman (2004) reported several sightings during a late autumn transect through the Ross Sea. Southern long-finned pilot whales are found circumpolar throughout the Southern Ocean in cold currents (Goodall and Galeazzi, 1985). The Australian ‘Southern Ocean Cetacean Ecosystem Program’ (SOCEP) surveys, whales were found near ice as south as 64° South (Waerebeek et al. 2004) and Brownell (1974) reported sightings near Scott Island (67°S, 179°W).
Supporting Information
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