Size in Square Kilometres
Qualifying Species and Criteria
Antarctic fur seal – Arctocephalus gazella
Criterion B (2); C (1; 2)
Southern elephant seal – Mirounga leonina
Criterion C (1; 2)
Marine Mammal Diversity
Megaptera novaeangliae, Ommatophoca rossii
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Bouvetøya (Bouvet Island) is one of the most isolated islands on earth. Situated in the southern Atlantic Ocean, it hosts the second largest breeding population of Antarctic fur seals (Arctocephalus gazella) in the world as well as a small breeding population of southern elephant seals (Mirounga leonina). The isolation of the island accentuates its importance as a breeding haulout for pinnipeds that forage in the region. Tracking data has demonstrated how the waters surrounding the island within a radius of around 400 km serve as foraging grounds for resident Antarctic fur seals and elephant seals, but also pinnipeds that breed elsewhere, but visit these rich feeding grounds (e.g. Ross seals, Ommatophoca rossii, from Antarctica). Humpback whales (Megaptera novaeangliae) that breed along the coast of Africa also forage on the dense krill (Euphausia superba) biomass in the waters around the island. Despite being declared a Norwegian Nature Reserve in 1971, the exclusive economic zone (EEZ) around the island has experienced significant illegal and unreported fishing activity, justifying further conservation status efforts.
Description of Qualifying Criteria
Criterion B: Distribution and Abundance
Sub-criterion B2: Aggregations
Nyrøysa beach, on the west coast of Bouvet, represents arguably the largest single Antarctic fur seal aggregation globally (Hofmeyr et al. 2005). This one breeding aggregation presumably established in the mid-1950’s when a large landslide created the available substrate at Nyrøysa, has increased rapidly and currently supports ~2.5% of the global breeding population of the species.
Criterion C: Key Life Cycle Activities
Sub-criterion C1: Reproductive Areas
Antarctic fur seal pup production at Bouvet Island increased rapidly in the 1980s and 1990s, and has since stabilized at around 15000 pups per year (1996-2002), indicating a total population of about 66000 at the single site (Nyrøysa) monitored on the island (Hofmeyr et al. 2005). While the Bouvet population is (at least) the second largest for this species, pup production at the Nyrøysa beach monitoring site accounts for ~2.5% of the global total. The most recent estimations of pup production during expeditions in 2007, 2014 and 2017 seem to indicate continued stability or possibly a slight decline in pup production (Norwegian Polar Institute, unpublished data).
A small population of southern elephant seals breed and moult on the beaches of Nyrøysa, Bouvetoya (Kirkman et al. 2001). Expedition timing has precluded consistent or confident enumeration of the breeding population of elephant seals, although the total island population certainly contributes a small percentage to the global total (McMahon et al. 2005). However, the remoteness of this site provides the only potential breeding or moulting substrate for land-breeding pinnipeds within this vast oceanic sector – functionally surpassing its apparent numerical importance in a global perspective.
Sub-criterion C2: Feeding Areas
Tracking data show that lactating Antarctic fur seals that pup at Nyrøysa forage in an area within 200 km around Bouvet Island, ranging from over the mid-Atlantic ridge to the north of the island, to roughly equidistant regions west, south and to a lesser extent east of the island (Biuw et al. 2009, Blanchet et al. 2013, Lowther et al. 2014; see Figs 1-3).
Antarctic fur seals feed mainly on krill in waters around Bouvetøya, though they also do take variable amounts of myctophid fish (Kirkman et al. 2000, Tarroux et al. 2016). Subadult male (n = 7) and adult female (n = 12) southern elephant seals tracked after moulting (2007/2008) from Bouvet foraged in a vast expanse of ocean over a period spanning ~ 10 months. Males foraged all the way south to the Antarctic continent, while females tended to stay north of the ice edge or alternatively remained close to Bouvetøya, targeting the ACC (Biuw et al. 2010, Fig 4). Southern elephant seals from other populations, notably the Prince Edward Islands, also forage close to Bouvet Island (e.g. McIntyre et al. 2017).
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Tarroux A, Lowther AD, Lydersen C, Kovacs KM. 2016. Temporal shift in the isotopic niche of female Antarctic fur seals from Bouvetøya. Polar Research 35: 31335.