Around 176 500 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.
This study forms part of the Ecosystems component of the British Antarctic Survey Polar Science for Planet Earth Programme, funded by The Natural Environment Research Council.
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