1
|
Calderan SV, Black A, Branch TA, Collins MA, Kelly N, Leaper R, Lurcock S, Miller BS, Moore M, Olson PA, Širović A, Wood AG, Jackson JA. South Georgia blue whales five decades after the end of whaling. ENDANGER SPECIES RES 2020. [DOI: 10.3354/esr01077] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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.
Collapse
Affiliation(s)
- SV Calderan
- Scottish Association for Marine Science (SAMS), Argyll PA37 1QA, UK
| | - A Black
- Government of South Georgia and South Sandwich Islands, Government House, Stanley FIQQ 1ZZ, Falkland Islands
| | - TA Branch
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195, USA
| | - MA Collins
- British Antarctic Survey, NERC, High Cross, Cambridge CB3 0ET, UK
| | - N Kelly
- Australian Antarctic Division, Department of Agriculture, Water and the Environment, Kingston, Tasmania 7050, Australia
| | - R Leaper
- International Fund for Animal Welfare, London SE1 8NL, UK
| | - S Lurcock
- South Georgia Heritage Trust, Dundee DD1 5BT, UK
| | - BS Miller
- Australian Antarctic Division, Department of Agriculture, Water and the Environment, Kingston, Tasmania 7050, Australia
| | - M Moore
- Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - PA Olson
- Southwest Fisheries Science Center, NMFS/NOAA, La Jolla, CA 92037, USA
| | - A Širović
- Texas A&M University at Galveston, Galveston, TX 77553, USA
| | - AG Wood
- British Antarctic Survey, NERC, High Cross, Cambridge CB3 0ET, UK
| | - JA Jackson
- British Antarctic Survey, NERC, High Cross, Cambridge CB3 0ET, UK
| |
Collapse
|
2
|
Jackson JA, Kennedy A, Moore M, Andriolo A, Bamford CCG, Calderan S, Cheeseman T, Gittins G, Groch K, Kelly N, Leaper R, Leslie MS, Lurcock S, Miller BS, Richardson J, Rowntree V, Smith P, Stepien E, Stowasser G, Trathan P, Vermeulen E, Zerbini AN, Carroll EL. Have whales returned to a historical hotspot of industrial whaling? The pattern of southern right whale Eubalaena australis recovery at South Georgia. ENDANGER SPECIES RES 2020. [DOI: 10.3354/esr01072] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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.
Collapse
Affiliation(s)
- JA Jackson
- British Antarctic Survey, High Cross, Cambridge CB3 0ET, UK For a full list of affiliations see Supplement 1 at www.int-res.com/articles/suppl/n043p323_supp1.pdf
| | | | | | | | - CCG Bamford
- British Antarctic Survey, High Cross, Cambridge CB3 0ET, UK For a full list of affiliations see Supplement 1 at www.int-res.com/articles/suppl/n043p323_supp1.pdf
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - G Stowasser
- British Antarctic Survey, High Cross, Cambridge CB3 0ET, UK For a full list of affiliations see Supplement 1 at www.int-res.com/articles/suppl/n043p323_supp1.pdf
| | - P Trathan
- British Antarctic Survey, High Cross, Cambridge CB3 0ET, UK For a full list of affiliations see Supplement 1 at www.int-res.com/articles/suppl/n043p323_supp1.pdf
| | | | | | | |
Collapse
|