Kelly Natalie

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Kelly
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Natalie
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  • Article
    Counting whales in a challenging, changing environment
    (Nature Publishing Group, 2014-03-13) Williams, R. ; Kelly, N. ; Boebel, Olaf ; Friedlaender, Ari S. ; Herr, H. ; Kock, K.-H. ; Lehnert, L. S. ; Maksym, Ted ; Roberts, Jason J. ; Scheidat, M. ; Siebert, U. ; Brierley, A. S.
    Estimating abundance of Antarctic minke whales is central to the International Whaling Commission's conservation and management work and understanding impacts of climate change on polar marine ecosystems. Detecting abundance trends is problematic, in part because minke whales are frequently sighted within Antarctic sea ice where navigational safety concerns prevent ships from surveying. Using icebreaker-supported helicopters, we conducted aerial surveys across a gradient of ice conditions to estimate minke whale density in the Weddell Sea. The surveys revealed substantial numbers of whales inside the sea ice. The Antarctic summer sea ice is undergoing rapid regional change in annual extent, distribution, and length of ice-covered season. These trends, along with substantial interannual variability in ice conditions, affect the proportion of whales available to be counted by traditional shipboard surveys. The strong association between whales and the dynamic, changing sea ice requires reexamination of the power to detect trends in whale abundance or predict ecosystem responses to climate change.
  • Article
    Have whales returned to a historical hotspot of industrial whaling? the pattern of southern right whale Eubalaena australis recovery at South Georgia
    (Inter Research, 2020-11-05) Jackson, Jennifer A. ; Kennedy, Amy S. ; Moore, Michael J. ; Andriolo, Artur ; Bamford, Connor C. G. ; Calderan, Susannah ; Cheeseman, Ted ; Gittins, George ; Groch, Karina ; Kelly, Natalie ; Leaper, Russell ; Leslie, Matthew S. ; Lurcock, Sarah ; Miller, Brian S. ; Richardson, Jessica ; Rowntree, Victoria ; Smith, Patrick ; Stepien, Emilie N. ; Stowasser, Gabriele ; Trathan, Phil N. ; Vermeulen, Els ; Zerbini, Alexandre N. ; Carroll, Emma
    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.
  • Article
    Georgia blue whales five decades after the end of whaling
    (Inter Research, 2020-11-19) Calderan, Susannah ; Black, Andy ; Branch, Trevor A. ; Collins, Martin A. ; Kelly, Natalie ; Leaper, Russell ; Lurcock, Sarah ; Miller, Brian S. ; Moore, Michael J. ; Olson, Paula A. ; Širović, Ana ; Wood, Andrew G. ; Jackson, Jennifer A.
    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.