Western Antarctic Peninsula and Islands IMMA

Size in Square Kilometres

2,441,313 km2

Qualifying Species and Criteria

Humpback whale – Megaptera novaeangliae

Criterion B (ii); C (ii)

Fin whale – Balaenoptera physalus

Criterion A; B (ii); C (ii)

Antarctic minke whale – Balaenoptera bonaerensis

Criterion C (ii)

Killer whale – Orcinus orca

Criterion B (i; ii); C (ii); D (i)

Antarctic fur seal – Arctocephalus gazella

Criterion B (ii); C (i; ii)

Southern elephant seal – Mirounga leonina

Criterion C (i; ii)

Leopard seal – Hydrurga leptonyx

Criterion B (ii); C (i; ii)

Crabeater seal – Lobodon carcinophaga

Criterion B (ii); C (i; ii)

Weddell seal – Leptonychotes weddellii

Criterion B (ii); C (i; ii)

Marine Mammal Diversity 

Criterion Dii

Balaenoptera borealis, Balaenoptera musculus intermedia, Balaenoptera acutorostrata, Eubalaena australis, Hyperoodon planifrons
Berardius arnuxii, Lagenorhynchus cruciger

Summary

The West Antarctic Peninsula and Islands IMMA is an important feeding area for large baleen whales, killer whales, and five species of seals. Humpback whales are the most abundant whale species in the area and largely occupy the coastal areas on the shelf. Vulnerable fin whales, with increasing numbers reported in recent years, tend to concentrate along the shelf edge and in waters beyond the shelf. The Near Threatened Antarctic minke whales mainly inhabit the coastal inshore waters of fjords and bays along the Antarctic Peninsula. Several killer whale ecotypes are distributed throughout the area, with relatively high concentrations in areas such as Gerlache and Bransfield Straits. Antarctic fur, southern elephant, crabeater, leopard, and Weddell seals reside, breed and forage in the West Antarctic Peninsula. In addition to these abundant species, Endangered sei and blue whales, as well as southern right whales, occasionally occur in this area.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

This area hosts high post-whaling densities of Vulnerable fin whales (Balaenoptera physalus) (Herr et al. 2016, Viquerat and Herr 2017). Southern Hemisphere fin whales were heavily exploited in the Southern Ocean during the commercial whaling period. Catch data suggest that they once were one of the most abundant Southern Hemisphere whale species and that they were reduced to ~2% of their pre-whaling population size (Clapham and Baker 2002). Today, the recovery status of the Southern Hemisphere fin whale population is unknown. Based on IDCR/SOWER data from surveys between 1991 and 1998, circumpolar fin whale abundance south of 60°S was last estimated at 5,445 (95 % CI 2,000–14,500) individuals (Branch and Butterworth 2001). However, this estimate almost certainly represents an unknown fraction of the total abundance of Southern Hemisphere fin whales only, as they are assumed to be extensively distributed in latitudes between 40°S and 60°S (Reilly et al. 2013) and less common south of 60°S. Recently, high sighting numbers and observations of large aggregations of fin whales in the area of the West Antarctic Peninsula have repeatedly been reported (Burkhard and Lanfredi 2012, Joiris and Dochy 2013, Santora et al. 2014; Baumann-Pickering et al. 2015; Edwards et al. 2015; Orgeira et al. 2015; Herr et al. 2016: Viquerat and Herr 2017, Seyboth 2018). In 2013, abundance of fin whales around the South Shetland Islands alone was estimated at 4,898 (95% CI 2,221–7,575) animals (Herr et al. 2016) based on an aerial line-transect survey. This estimate may be indicative of a large distributional change, with increasing numbers of fin whales moving to this area in the austral summer. Alternatively, this number is related to population recovery and increasing numbers of fin whales, returning to an area that was known for high fin whale densities during the whaling period (Kemp and Bennet 1932). Independent of these possible explanations, the number of fin whales using the shelf waters of the West Antarctic Peninsula between January and June is indisputably high and certainly represents a large fraction of the Southern Hemisphere fin whale population. The animals coming to the northern West Antarctic Peninsula in austral summer use the area as a feeding habitat, which apparently is capable of providing for a potentially recovering population and high numbers of individuals who rely on the high krill biomass of this region. Very recently, increasing use also of the inshore waters of the Bransfield Strait by fin whales has been observed (Seyboth 2018, Dalla Rosa et al. unpublished data).

Criterion B: Distribution and Abundance

Sub-criterion Bi: Small and Resident Populations 

The Gerlache type B killer whale (B2) is currently known only from the Western Antarctic Peninsula (Durban et al. 2016). Although all killer whale ecotypes that occur in the WAP region migrate to low latitudes, they spend relatively little time there, returning to Antarctic waters following short seasonal migrations (Durban and Pitman 2012, Pitman et al. unpublished data).

Sub-criterion Bi: Aggregations

High densities of marine mammals at the West Antarctic Peninsula are supported by the extremely high krill biomass in this area (Nicol 2006, Ducklow et al. 2007, Orgeira et al. 2015, 2017). Historical whaling records underline the importance of the area for whales, with large numbers of catch records indicating high abundances of humpback, fin and blue whales before over-exploitation by commercial whaling (Kemp and Bennett 1932). Fin whales regularly aggregate in the shelf waters along the continental shelf break around the South Shetland Islands, Elephant Island and the South Orkney Islands between January and June (Burkhard and Lanfredi 2012; Joiris and Dochy 2013; Santora et al. 2014; Reyes Reyes et al. 2014, 2015; Baumann-Pickering et al. 2015; Edwards et al. 2015; Orgeira et al. 2015; Herr et al. 2016, Viquerat and Herr 2017, Seyboth 2018). As described for criterion A, abundance of fin whales is high and has to be considered to represent a considerable share of the Southern Hemisphere population. Densities have been estimated at 0.0268 ± 0.0183 ind. km−2 around Elephant Island, and at 0.0588 ± 0.0381 ind. km−2 around the South Orkney Islands based on a shipboard visual survey in 2016 (Viquerat and Herr 2016). A ship-based helicopter survey estimated fin whale density at the South Shetland Islands at 0.117 (0.053–0.181) ind. km-2 (Herr et al. 2016). The high occurrence of fin whales in the proposed area has been related to krill distribution and favourable oceanographic parameters (Santora et al. 2014, Herr et al. 2016, Viquerat et al. 2017, Seyboth 2018).

Humpback whales occur in high densities throughout the inshore waters of the area, in particular in areas such as the Bransfield Strait, the Gerlache Strait and its surrounding bays, as well as other straits and bays further south, including Marguerite Bay (Secchi et al. 2001, 2011, Friedlaender et al. 2006, 2011, Dalla Rosa 2010, Dalla Rosa et al. 2012, Nowacek et al. 2011, Johnston et al. 2012). The humpback whales migrating to this area belong to Breeding Stock G (Stevick et al. 2004, Acevedo et al. 2017). Encounter rates are available for Bransfield and Gerlache Straits (Secchi et al. 2001, 2011). Abundance has been estimated for just a portion of Bransfield Strait at 865 (95% CI 656 -1,141) individuals in 2006 (Secchi et al. 2011, Fig. 6) and at 3,024 (95%CI 944–5105) for the Bransfield Strait and adjacent areas in 2013 (Herr et al. 2016).

High encounter rates of killer whales, especially Gerlache type B, have been registered in the Gerlache Strait, although they may be found regularly throughout the West Antarctic Peninsula (Pitman and Ensor 2003, Dalla Rosa et al. 2007, unpublished data). Tracking data has revealed the importance, during post mating dispersal, of the South Orkneys and Antarctic Peninsula regions to the male Antarctic fur seals that breed on South Georgia. These male seals have been tracked as far south as Adelaide Island where numbers of males hauling out have increased over the last three decades (Lowther et al. unpublished). The connectivity between the largest breeding population, which represents 95% of the world population, and the South Orkney Islands is evidenced by the build-up of large numbers of males after the December mating season (Carlini 2006). This movement by nearly 50% of the world’s population of this species represents a significant immigration to and use of this region. The accessible beaches and pack-ice in this region provides important substrate for these animals to haul-out to rest, thermoregulate and avoid predation. Additionally, female Antarctic fur seals from Cape Shirreff are central place foragers in the region during the summer months (December-April, Hinke et al. 2017, Goebel et al. 2000). Females tracked from this site during the non-breeding period also utilise the Marguerite Bay region in April/May prior to migrating further north (Arthur et al. 2017, 2018). Approximately 15% of the crabeater, 15% of leopard and 24% of the Weddell seal population (from surveyed areas) reside, breed and forage in the Western Antarctic Peninsula (Southwell et al. 2012).

Criterion C: Key Life Cycle Activities

Sub-criterion Ci: Reproductive Areas

The Western Antarctic Peninsula region encompassing the IMMA is a breeding area for a proportion of crabeater, leopard and Weddell seal populations (Southwell et al. 2012). Also, the most southerly Antarctic fur seal and southern elephant seal breeding colonies are located in the South Shetland Islands and Elephant Island (Le Boeuf and Laws 1994, Goebel et al. 2000).

Sub-criterion Cii: Feeding Areas

The Western Antarctic Peninsula region is characterized by a complex bathymetry and circulation, which favours enhanced biological productivity, influencing the distribution and abundance of cetaceans (e.g. Friedlaender et al. 2006, Dalla Rosa 2010). The area is known for extremely high krill biomass (Nicol 2006) supporting high predator densities. The area serves as a feeding ground for several baleen whale species, which migrate from their breeding grounds in more temperate waters to feed on krill during the austral summer. A variety of sympatric krill predators has been shown to occur in the area (Friedlaender et al. 2008, Santora and Veit 2013). Satellite tracking of humpback (Dalla Rosa et al. 2008; Curtice et al. 2015, Weinstein and Friedlaender 2017) and fin whales (Dalla Rosa et al. unpublished data) has shown that individuals consistently use this area for extended periods of time during the feeding season. Feeding behaviour has been described for humpback whales by means of telemetry (Friedlaender et al. 2013). Visual observations of bubble nets and other observed feeding behaviour prove feeding of humpback and fin whales in the area (Acevedo et al. 2008, Herr et al. 2016). Large aggregations of up to 60 surface feeding fin and humpback whales have been observed in the proposed area, preying on krill (Nowacek et al. 2011, Burkhardt and Lanfredi 2012, Joiris and Dochy 2013, Herr et al. 2016). Their distribution has been proposed to be linked to high densities of krill (Santora et al. 2014, Herr et al 2016). For humpback whales the area encompasses the major part of the feeding grounds of Breeding Stock G (Stevick et al. 2004, Dalla Rosa et al. 2012, Acevedo et al. 2017).

All Antarctic killer whale ecotypes also use this area for feeding, as differences in foraging ecology or prey preferences have helped to distinguish among them (e.g. Durban et al. 2016). Approximately 15% of the crabeater seal population (from surveyed areas) reside, breed and forage in the WAP (Southwell et al. 2012). The majority of crabeater seal feeding dives occur within the top 50 m, although they can dive up to 600 m with a maximum duration of 24 minutes (Burns et al. 2004, 2008). They appear to favour foraging locations on the continental shelf within the 50 to 450 m depth range, with a tendency to avoid depths of 600 m or greater. Crabeater Seals feed primarily on Antarctic Krill (Euphausia superba), which accounts for over 90% of their diet, with the remainder made up of fish and squid. Deeper dives at dawn and dusk indicate that their feeding activity is tied to the daily vertical migrations of Krill. Daytime foraging appears to exploit zooplankton schools compressed along the bottom. Their high density within the Western Antarctic Peninsula is likely related to the abundance of krill in this region. Winter tracking data suggests that they alter their behaviour to accommodate seasonal and/or annual fluctuations in seasonal sea ice and associate with bathymetric features likely to concentrate prey patches (Burns et al. 2004). They are most likely located in nearshore waters where bathymetric gradients and ice concentration are high (Burns et al. 2004).

The Western Antarctic Peninsula is home to 24% of the Weddell seal population (from surveyed areas, Southwell et al. 2012). The abundance of prey and availability of suitable sea-ice habitat makes this area ideal for this pagophilic species. Weddell seals are generalist predators, and their diet likely varies at a regional scale. In the Western Antarctic Peninsula they are known to feed on Antarctic krill, notothenioid fish (icefishes), particularly the Antarctic silverfish, but the diet also includes Antarctic toothfish, myctophids and cephalopods. Weddell seals typically forage within two depth layers, surface waters (0-160m) and near the bottom. While both pelagic and benthic diving occur during daylight, seals forage almost exclusively in the upper water column at night (Plötz et al. 2001). Leopard seals have a circumpolar distribution concentrated in, but not limited to, the Southern Ocean. They are most commonly found in and around the outer fringes of the pack ice or close to the Antarctic Continent. The Western Antarctic Peninsula represents 15% of the surveyed populations (Southwell et al. 2012). They are top predators in the Antarctic marine ecosystem and feed on a diverse range of prey that varies seasonally, spatially and ontogenically including krill, fish, squid, penguins and other pinnipeds. Penguins are eaten throughout the year but form an especially large proportion of the leopard seal diet in January to March, when these birds are breeding (Siniff and Stone 1985). Newly weaned crabeater seal pups can also be an important part of the diet in the pack ice near the Antarctic Peninsula (Siniff and Stone 1985). Leopard seal predation has been implicated in slowing the recovery of the Antarctic fur seal population at Elephant Island (Boveng et al. 1998). At Cape Shirreff, studies monitoring leopard seal predation on Antarctic fur seal pups suggest that they consume up to half of the annual pup production within this area. In addition to fur seal pups and penguins, leopard seals were found to take two species of demersal fish (Gobionotothen gibberifrons and Notothenia coriiceps) and scavenge carcasses of fur seals and penguins.

Male Antarctic fur seals from South Georgia have been tracked traveling to and moving within the South Orkney Islands and Western Antarctic Peninsula region (Boyd et al. 1998, BAS unpublished). This southwards migration of a large predator biomass has significant implications for consumption of krill, fish and penguins within the region (Davis et al. 2006). The growing body of at sea movement data shows that male fur seals at South Georgia display some level of central place foraging alternating time at sea with periods ashore resting, very similar to lactating females. These seals also predominantly foraged on-shelf, close to their haul out locations (<100 km), and so have a greater spatial overlap with penguins than the more pelagic foraging female seals. Post breeding males often have very poor body condition resulting from their prolonged fast whilst competing for territory and potential mates. The abundant food resources in the South Orkney Islands and the Western Antarctic Peninsula, in close proximity to accessible haul-out locations makes this an ideal area for these predators. The post-breeding foraging areas of southern elephant seals are close to their breeding grounds for both males and females (Huckstadt et al. 2012; Muelbert et al. 2013, Hindell et al. 2016). They feed along the continental shelf and in the trough areas, and satellite tracking shows they range throughout the entire area the IMMA. Criterion D: Special Attributes

Sub-criterion Di: Distinctiveness

Though three killer whale ecotypes frequently occur in this area (Pitman and Ensor 2003, Dalla Rosa et al. 2007, Durban et al. 2016), this area is particularly important for Gerlache type B ecotype, as these are only found around the Antarctic Peninsula (Durban et al. 2016).

Sub-criterion Dii: Diversity

Species richness and abundance of seabirds and marine mammals and areas that are persistently attractive to top predators have been demonstrated for the proposed area (Lazaneo et al. 2013, Santora and Veit 2013). At least 9 marine mammal species occur regularly in the proposed area (humpback, fin, Antarctic minke and killer whales, Antarctic fur, leopard, Weddell, crabeater and elephant seals). The highest cetacean diversity has been recorded in the northern Antarctic Peninsula, including the area around Elephant Island (e.g. Lazaneo et al. 2013). Additional records of marine mammals throughout the proposed area include encounters of sei whales (Balaenoptera borealis) (Secchi et al. 2001), dwarf minke whales (Balaenoptera acutorostrata) (Acevedo et al. 2011), Antarctic blue whales (Balaenoptera musculus intermedia) (Herr et al. 2016) and southern right whales (Eubalaena australis) (Stone and Hammer 1988, Aguayo-Lobo et al. 2008, Johnston et al. 2012, Dalla Rosa, unpublished data, Herr et al. unpublished data). Odontocete species that have been reported from the proposed area include hourglass dolphins (Lagenorhynchus cruciger) (Santora 2012, Dellabianca et al. 2012), southern bottlenose whales (Hyperoodon planifrons) (Santora and Brown 2010, Herr et al. unpublished data) and Arnoux’s beaked whales (Berardius arnuxii) (Johnston et al. 2012, Friedlaender et al. 2010, Herr et al. unpublished data).

Supporting Information

Anonymous, 2012. ‘National Conservation Strategy and Action plans for Dugongs and their habitats in India.’ Ministry of Environment, Forests and Climate Change, New Delhi.

Apte, D., D. Parasharya & B. Patel. 2019. Feeding trails of Dugong Dugong dugon (Müller, 1776) (Mammalia: Sirenia: Dugongidae) in the Gulf of Kachchh, western coast of India. Journal of Threatened Taxa 11(1): 13151–13154; https://doi.org/10.11609/jott.4315.11.1.13151-13154

Pathan, S. 2019. Field Report Submitted to the CAMPA Dugong Recovery Project, Wildlife institute of India, Dehradun, India.

Sivakumar, K. and Nair, A. 2013. Dugong Distribution, Habitat and Risks Due to Fisheries and Other Anthropogenic Activities in India. Wildlife Institute of India – Technical Report. 1-74

Sutaria, D., Panicker, D., Jog, K., Sule, M., Muralidharan, R., and Bopardikar, I. 2015. Humpback Dolphins (Genus Sousa) in India: An Overview of Status and Conservation Issues. In ‘Conservation status of Humpback Dolphins (Sousa spp.). T.A.Jefferson and B.E.Curry (Ed.) Advances in Marine Biology Series. Vol. 72. Elsevier/Academic Press.

Sutaria, D., Arthur, R., & Satashivam, K. 2014. Marine mammals in subcontinental waters. In Mammals of South Asia: Johnsingh, A. J. T. & Manjrekar, N. (Ed.). New Delhi: Permanent Black.

Sutaria, D., and Jefferson, T. A. 2004. Records of Indo-Pacific Humpback Dolphin (Sousa chinensis Osbeck, 1765) along the coast of India and Sri Lanka – An Overview. Aquatic Mammals Special Issue 30(1) 125-136

MMRCNI 2019. Database on Sousa plumbea and Neophocaena phocaenoides from Gujarat: www.marinemammals.in

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