Abstract
We conducted aerial surveys in the austral summer of 2009-2010 to count and record the spatial distribution patterns of pack-ice seals hauled-out along the Ingrid Christensen and Princess Astrid coast of East Antarctica. A total of 3,601 hauled-out seals were counted from six aerial surveys totalling a length of approx. 1,200km, with each survey lasting about two hours. Weddell Seal Leptonychotes weddellii was the most commonly sighted species in both the areas surveyed (98.2%), and had an encounter rate of 2.9 seals/km. The other species encountered during the survey were Crabeater Seal Lobodon carcinophaga (1.7%) and Leopard Seal Hydrurga leptonyx (0.03%). Group size of hauled-out Weddell Seals varied considerably and ranged from solitary to maximum of 42 individuals. The median group size of Weddell seals hauled-out along the Ingrid Christenson Coast was found to be significantly different between the December 2009 and January 2010 survey. Further, along this coast Weddell Seals were found hauled-out mainly close to the ice shelf and their spatial distribution appeared to be influenced by the extent of sea ice in the area.
Highlights
Five of the 18 extant species of true or earless seals of the family Phocidae: the Southern Elephant Seal Mirounga leonina, Weddell Seal Leptonychotes weddellii, Crabeater Seal Lobodon carcinophaga, Leopard Seal Hydrurga leptonyx and Ross Seal Ommatophoca rossii occur exclusively in the southern Hemisphere
Seal survey A total of six aerial surveys were flown during this study, totalling a length of approx. 1200km, comprising four surveys in the Prydz Bay region totalling 800km, and two surveys along the Fimbul Ice Shelf totalling 400km
Except for the Southern Elephant Seal and Ross Seal all the other species of pack-ice seals were recorded during the aerial surveys (Image 2)
Summary
Five of the 18 extant species of true or earless seals of the family Phocidae: the Southern Elephant Seal Mirounga leonina, Weddell Seal Leptonychotes weddellii, Crabeater Seal Lobodon carcinophaga, Leopard Seal Hydrurga leptonyx and Ross Seal Ommatophoca rossii occur exclusively in the southern Hemisphere They have a circumpolar distribution around the Antarctic Continent and occur a little further north in the southern Ocean and on sub-antarctic islands (Folkens et al 2008). In the 19th and early 20th centuries, the Southern Elephant Seal was hunted almost to extinction, while the other species were free from commercial exploitation (Shirihai 2008) These other species escaped by virtue of their range being in dangerous and ice-filled seas (Testa & Siniff 1987).
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