ESR 43:359-373 (2020) - DOI: https://doi.org/10.3354/esr01077
South Georgia blue whales five decades after the end of whaling
Susannah V. Calderan1,*, Andy Black2, Trevor A. Branch3, Martin A. Collins4, Natalie Kelly5, Russell Leaper6, Sarah Lurcock7, Brian S. Miller5, Michael Moore8, Paula A. Olson9, Ana Širović10, Andrew G. Wood4, Jennifer A. Jackson4
ABSTRACT: Blue whales Balaenoptera musculus at South Georgia were heavily exploited during 20th century industrial whaling, to the point of local near-extirpation. Although legal whaling for blue whales ceased in the 1960s, and there were indications of blue whale recovery across the wider Southern Ocean area, blue whales were seldom seen in South Georgia waters in subsequent years. We collated 30 yr of data comprising opportunistic sightings, systematic visual and acoustic surveys and photo-identification to assess the current distribution of blue whales in the waters surrounding South Georgia. Over 34000 km of systematic survey data between 1998 and 2018 resulted in only a single blue whale sighting, although opportunistic sightings were reported over that time period. However, since 2018 there have been increases in both sightings of blue whales and detections of their vocalisations. A survey in 2020 comprising visual line transect surveys and directional frequency analysis and recording (DIFAR) sonobuoy deployments resulted in 58 blue whale sightings from 2430 km of visual effort, including the photo-identification of 23 individual blue whales. Blue whale vocalisations were detected on all 31 sonobuoys deployed (114 h). In total, 41 blue whales were photo-identified from South Georgia between 2011 and 2020, none of which matched the 517 whales in the current Antarctic catalogue. These recent data suggest that blue whales have started to return to South Georgia waters, but continued visual and acoustic surveys are required to monitor any future changes in their distribution and abundance.
KEY WORDS: Blue whale · Balaenoptera musculus · South Georgia · Recovery · Whaling · Southern Ocean
Full text in pdf format  | Cite this article as: Calderan SV, Black A, Branch TA, Collins MA and others (2020) South Georgia blue whales five decades after the end of whaling. Endang Species Res 43:359-373. https://doi.org/10.3354/esr01077
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