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

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0248071
Author(s):  
Connor C. G. Bamford ◽  
Victoria Warwick-Evans ◽  
Iain J. Staniland ◽  
Jennifer A. Jackson ◽  
Philip N. Trathan
Keyword(s):  
Antarctic Krill ◽  
Euphausia Superba ◽  
Arctocephalus Gazella ◽  
Habitat Models ◽  
South Georgia ◽  
Fur Seals ◽  
Fur Seal ◽  
Ice Edge ◽  
Future Work ◽  
Antarctic Fur Seals

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.

Dispersal of male and female Antarctic fur seals (Arctocephalus gazella)

1998 ◽  
Vol 55 (4) ◽  
pp. 845-852 ◽  
Author(s):  
I L Boyd ◽  
D J McCafferty ◽  
K Reid ◽  
R Taylor ◽  
T R Walker
Keyword(s):  
Arctocephalus Gazella ◽  
Adult Males ◽  
The South ◽  
Male And Female ◽  
Breeding Sites ◽  
South Georgia ◽  
Orkney Islands ◽  
Fur Seals ◽  
South Orkney Islands ◽  
Antarctic Fur Seals

This study examined the foraging locations of adult male and female Antarctic fur seals (Arctocephalus gazella) in the Scotia Sea during the postbreeding period. Satellite transmitters were used to track adult males and females and to obtain information about dive depths. Male fur seals migrated away from the breeding area during the postbreeding period whereas females remained close to the breeding grounds and foraged in the same area during two consecutive years. The most intensive foraging by females was associated with the edge of the continental shelf of South Georgia. Males dived deeper than females. Counts of males at South Georgia and at the South Orkney Islands support the result from satellite tracking data showing that males move from South Georgia to the South Orkney Islands at the end of the breeding season. Unlike males, females were limited in their foraging range by the necessity to return to feed dependent young, so breeding sites are likely to be located close to foraging areas that are optimal for females. Locations used for feeding by females were avoided by males, either because they were suboptimal for males or because foraging by females at South Georgia causes local depletion of food, and males, which have the option to forage further afield, can forage more successfully in regions where there are no females. Comparison with fisheries data also suggests that these fur seals are targeting the most abundant exploitable prey.

Pup production and distribution of breeding Antarctic fur seals (Arctocephalus gazella) at South Georgia

1993 ◽  
Vol 5 (1) ◽  
pp. 17-24 ◽  
Author(s):  
I. L. Boyd
Keyword(s):  
Initial Period ◽  
Population Expansion ◽  
Breeding Population ◽  
Arctocephalus Gazella ◽  
South Georgia ◽  
Long Term Study ◽  
Fur Seals ◽  
Production And Distribution ◽  
Breeding Grounds ◽  
Antarctic Fur Seals

A census of the breeding population of Antarctic fur seals (Arctocephalus gazella) at South Georgia was carried out during the 1990/91 breeding season. Using counts of adult females ashore at the breeding grounds during the pupping period, together with corrections for the likelihood of a female being ashore at a census and for pregnancy rate (71% in 1990/91), pup production was estimated as 269 000 (95% confidence intervals 188 000-350000). The breeding population in 1990/91 was reduced at long-term study sites probably because of limited food availability. Data from these sites were used to estimate the pup production of the population had 1990/91 been a typical year. Based on values from 1983/84 to 1990/91, pup production in 1990/91 would have been 378000 (se=19100) if it had been an average year. The annual increase in pup production from 1976/77 to 1990/91 has declined to 9.8% since the initial period of population expansion in the 1950s and 1960s. Increased population size has led to an expansion of the breeding range at South Georgia.

Fish in the diet of Antarctic fur seals (Arctocephalus gazella) at South Georgia during winter and spring

1996 ◽  
Vol 8 (2) ◽  
pp. 155-160 ◽  
Author(s):  
A.W. North
Keyword(s):  
Arctocephalus Gazella ◽  
South Georgia ◽  
Fur Seals ◽  
Fur Seal ◽  
Total Fish ◽  
Fish Remains ◽  
Gobionotothen Gibberifrons ◽  
Lepidonotothen Larseni ◽  
The Antarctic ◽  
Fish Otoliths

The occurrence of fish in the diet of the Antarctic fur seal (Arctocephalus gazella) at Bird Island, South Georgia was investigated by analysis of fish otoliths in scats (faeces) collected during late May to early November 1983. Of the 55 scats examined, 49 contained fish remains, and 45 contained fish otoliths. Ten fish species were represented by 415 otoliths, and 33 otoliths were too digested to be identified unequivocally. Fish size was estimated from otolith size based on published allometric equations. Four coastal notothenioid fishes dominated the fish component of the diet: Champsocephalus gunnari and Gobionotothen gibberifrons each comprised about 40% of the total fish mass; Chaenocephalus aceratus was ranked third by mass and the smaller Lepidonotothen larseni occurred in one quarter of the scats but was of lower importance in terms of mass. The length-frequency distribution of C. gunnari landed by the commercial fishery in October 1982 to June 1983 is similar to that which comprised the bulk of the diet in the present study. Compared with recent studies on the fish component of the diet in the literature, the dominance of C. gunnari is generally similar, however, there was a greater proportion of G. gibberifrons during the 1983 winter and spring than reported for recent winters.

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

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
David March ◽  
Massimiliano Drago ◽  
Manel Gazo ◽  
Mariluz Parga ◽  
Diego Rita ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Adult Male ◽  
Antarctic Krill ◽  
South Shetland Islands ◽  
Distribution Area ◽  
Arctocephalus Gazella ◽  
Western Antarctic Peninsula ◽  
Adult Males ◽  
Fur Seals ◽  
Antarctic Fur Seals

AbstractDetailed 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.

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