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ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01072

Have whales returned to a historical hotspot of industrial whaling? The pattern of southern right whale (Eubalaena australis) recovery at South Georgia

Jennifer A. Jackson*, Amy Kennedy, Michael Moore, Artur Andriolo, Connor C. G. Bamford, Susannah Calderan, Ted Cheeseman, George Gittins, Karina Groch, Natalie Kelly, Russell Leaper, Matthew S. Leslie, Sarah Lurcock, Brian S. Miller, Jessica Richardson, Vicky Rowntree, Patrick Smith, Emilie Stepien, Gabriele Stowasser, Phil Trathan, Els Vermeulen, Alexandre N. Zerbini, Emma L. Carroll

*Corresponding author:

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 SRW 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-identifications. During 76 hours of visual observation effort over 19 expedition days, SRWs were encountered 15 times (~31 individuals). Photo-identifications, 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-identification 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 SRW 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 SRW and an increasing humpback whale presence in South Georgia waters following the cessation of whaling.