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

Connor C. G. Bamford,Iain J. Staniland,Jennifer A. Jackson,Philip N. Trathan,Andrew J. Hoskins,Victoria Warwick-Evans

doi:10.1371/journal.pone.0248071

Connor C. G. Bamford, Iain J. Staniland + Show 4 more

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https://doi.org/10.1371/journal.pone.0248071

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Abstract

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.

Highlights

Antarctic fur seals (Arctocephalus gazella) were heavily exploited by commercial sealing in the South Atlantic following the initial discovery of their abundance in the Southern Ocean [1]
Platform terminal transmitters (PTT, Sirtrack, Havelock North, NZ; Kiwisat 101; 245g, x 6.5 x 1.9 cm) were fitted to lactating female fur seals breeding on Bird Island, South Georgia during the late summer; 8 were deployed in 1999 and 6 in 2003 following procedures described in [30]
For each year and period, area under the curve (AUC) values showed that the variables that best described the distribution of female fur seals were distance from the colony (CDIST–Table 2)

Summary

Introduction

Antarctic fur seals (Arctocephalus gazella) were heavily exploited by commercial sealing in the South Atlantic following the initial discovery of their abundance in the Southern Ocean [1]. Populations inhabiting the Sub-Antarctic archipelago of South Georgia (54 ̊17’S 36 ̊30’W) were commercially targeted from 1786 onwards, with the population close to extinction by 1820, and likely extirpated by the end of the 19th Century [2] when the industry shifted its focus to populations further south [1]. Since the cessation of commercial sealing [3] the population of fur seals breeding at South Georgia has grown rapidly.

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