Abstract
Around 176500 whales were killed in the sub-Antarctic waters off South Georgia (South Atlantic) between 1904 and 1965. In recent decades, whales have once again become summer visitors, with the southern right whale (SRW) the most commonly reported species until 2011. Here, we assess the distribution, temporal pattern, health status and likely prey of SRWs in these waters, combining observations from a summertime vessel-based expedition to South Georgia, stable isotope data collected from SRWs and putative prey and sightings reports collated by the South Georgia Museum. The expedition used directional acoustics and visual surveys to localise whales and collected skin biopsies and photo-IDs. During 76 h of visual observation effort over 19 expedition days, SRWs were encountered 15 times (~31 individuals). Photo-IDs, combined with publicly contributed images from commercial vessels, were reconciled and quality-controlled to form a catalogue of 6 fully (i.e. both sides) identified SRWs and 26 SRWs identified by either left or right sides. No photo-ID matches were found with lower-latitude calving grounds, but 3 whales had gull lesions supporting a direct link with Península Valdés, Argentina. The isotopic position of SRWs in the South Georgia food web suggests feeding on a combination of copepod and krill species. Opportunistic reports of SRW sightings and associated group sizes remain steady over time, while humpback whales provide a strong contrast, with increased sighting rates and group sizes seen since 2013. These data suggest a plateau in SRWs and an increasing humpback whale presence in South Georgia waters following the cessation of whaling.
Highlights
The sub-Antarctic island of South Georgia lies in the high latitudes of the South Atlantic, just south of the Polar Front and within the Antarctic Zone of the Antarctic Circumpolar Current (Fig. 1)
Weather and sea conditions were suitable for visual observations for 76 h and spanned 327 nautical miles of survey
Fifteen sightings of 31 southern right whale (SRW) were documented (Fig. 3); 11 of these encounters were of singletons or pairs, and the largest group sighted was estimated at 5 whales
Summary
Our area of focus in this study was the South Georgia marine ecosystem, spanning the coastal and shelf waters around South Georgia and the shelf waters of Shag Rocks to the west of the island (33.5°−43° W, 53°−56° S; Fig. 1). The voyage was conducted on the R/V ‘Song of the Whale’ (owned and managed by Marine Conservation Research1), which departed from the Falkland Islands (Islas Malvinas) on Monday 22 January 2018. The vessel sailed to the north coast of South Georgia, where she remained for 19 d (28 January to 16 February 2018) before returning to the Falkland Islands (Islas Malvinas) on Wednesday 21 February (a total of 31 d sailing). All data collection was carried out under permit RAP/2017/017 issued by the Government of South Georgia and the South Sandwich Islands (GSGSSI) following review and approval of all data collection approaches by the British Antarctic Survey (BAS) Animal Welfare and Ethics Review Board (review #1040).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
