Winter distribution of juvenile and sub-adult male Antarctic fur seals (Arctocephalus gazella) along the western Antarctic Peninsula

Detailed knowledge of habitat use by marine megafauna is critical to understand their ecological roles and for the adequate management of marine resources. Antarctic fur seals (Arctocephalus gazella) inhabiting the Atlantic sector of the Southern Ocean prey largely on Antarctic krill (Euphausia superba) and play a central role in managing the krill fishery. Here, we assessed the demographic structure of three post-mating, early moult male haul-outs in the South Shetland Islands in early March and calculated the relative contribution of juveniles (1–4 years old) and sub-adult males (5–6 years) to the population remaining in maritime Antarctica after the breeding season. We also satellite tagged 11 juvenile males and four sub-adult males to analyze their movements and develop a species distribution model including both age classes. Our results highlighted the dominance of young individuals in the male population, revealed that they do not behave as central place foragers and identified key environmental drivers that affected their distribution at-sea throughout winter. Predicted potential foraging habitat overlapped highly with the known distribution of Antarctic krill, and identified the waters off the western Antarctic Peninsula and the Scotia Sea as the core of the distribution area of juvenile and sub-adult male Antarctic fur seals in winter. This pattern is similar to that of adult males but totally different from that of adult females, as the latter overwinter in areas at latitude 45–55° S. This segregation has implications for the ecology and management of the krill fishery.

Wintertime overlaps between female Antarctic fur seals (Arctocephalus gazella) and the krill fishery at South Georgia, South Atlantic

The diet of Antarctic fur seals (Arctocephalus gazella) at South Georgia is dominated by Antarctic krill (Euphausia superba). During the breeding season, foraging trips by lactating female fur seals are constrained by their need to return to land to provision their pups. Post-breeding, seals disperse in order to feed and recover condition; estimates indicate c.70% of females remain near to South Georgia, whilst others head west towards the Patagonian Shelf or south to the ice-edge. The krill fishery at South Georgia operates only during the winter, providing the potential for fur seal: fishery interaction during these months. Here we use available winter (May to September) tracking data from Platform Terminal Transmitter (PTT) tags deployed on female fur seals at Bird Island, South Georgia. We develop habitat models describing their distribution during the winters of 1999 and 2003 with the aim of visualising and quantifying the degree of spatial overlap between female fur seals and krill harvesting in South Georgia waters. We show that spatial distribution of fur seals around South Georgia is extensive, and that the krill fishery overlaps with small, highly localised areas of available fur seal habitat. From these findings we discuss the implications for management, and future work.

Comparative analysis of the diet of Arctocephalus gazella (Pinnipedia), at two localities of the South Shetland Islands, with emphasis on the fish component

ABSTRACT We studied the diet of non-breeding male Antarctic fur Seals Arctocephalus gazella (Peters, 1875) at two different localities of the South Shetland Islands: Stranger Point, King George Island/Isla 25 de Mayo and Duthoit Point, Nelson Island, by the analysis of 65 faecal samples collected in February 2012. Overall, Antarctic krill Euphausia superba (Dana, 1850) and fish were the main prey taxa followed by penguins and cephalopods. Myctophids were dominant among fish; Gymnoscopelus nicholsi (Gilbert, 1911) was the most important prey species at both sampling sites, followed by Electrona antarctica (Gunther, 1878) at Stranger Point and by the nototheniid Pleuragramma antarctica (Boulenger, 1902) at Duthoit Point. The relative similarity found in the dietary composition of fur seals from both locations suggest they might have been sharing common feeding areas. Our results were compared with those reported in the literature for different localities of the South Shetland Islands and the Scotia Sea region. The absence of formerly harvested demersal notothenioid species in the diet of fur seals may reflect the negative impact that commercial fisheries had on some fish populations and supports the importance of implementing long-term monitoring studies on the feeding habits of A. gazella in the area.

Genome Sequence of a Novel Picorna-Like RNA Virus from Feces of the Antarctic Fur Seal (Arctocephalus gazella)

ABSTRACT A novel RNA virus was detected in a fecal sample collected from the Antarctic fur seal (Arctocephalus gazella) in King George Island, Antarctica. The almost-complete genome sequence reveals two open reading frames and a dicistrovirus-like gene order.