REPORT OF SIGHTING AND HELICOPTER SURVEYS FROM
POLARSTERN CRUISE ANTXVIII5b
14 April - 7 May 2001
Deborah Thiele, International Whaling Commission
The Polarstern departed on cruise AntXVIII5b on 14 April 2001 and headed directly for the SO GLOBEC study site (Figures 1 and 2). The focus area for Polarstern based marine science has generally been in the Weddell Sea, however some research has been conducted in the Western Peninsula and Bellinghausen Sea regions. Generally top predator studies on the Polarstern have been conducted by J. van Franeker (with a focus on seabird abundance and associated cetacean records), and some surveys have included cetacean visual surveys (Pankow and Kock 2000). J. van Franeker conducted seabird census from the upper bridge flying deck on AntXVIII5b, whilst the IWC observer worked from the inside bridge. Helicopter surveys reported here were conducted with JvF as he kindly shared his dedicated helicopter flight time for the voyage with the IWC observer.
Weather conditions on this cruise were not conducive to visual surveys, and few whales were sighted from the vessel. Most sightings were made on helicopter surveys (which were conducted in good weather only) and on the one sunny day within the ice to the south of Marguerite Bay (Figures 2 and 3). The survey area was reached on 18 April and line transect sampling began on a northern transect placed between those soon to be occupied by the US survey vessel Nathaniel B Palmer. Hourglass dolphins (1:10), like fin whales (1:2) and an unidentified whale were recorded in the transect area.
The Polarstern remained working in the survey area until 21 April, and then steamed to the oceanic fast ice edge well to the south of Marguerite Bay (Figures 1 and 2). The ship proceeded well within the ice to locate sea ice sampling stations. At the first station on 23 April in a small lead near an iceberg a group of four dark shouldered minke whales were sighted, and spent the whole afternoon around the vessel whilst on station (Figure 3). This area, and the area traversed through ice to reach it had 10/10 ice coverage and extensive algal deposits on the underside of floes. On 24 April two groups of minke whales (six animals were observed in the ice near the vessel). On 25 April a series of helicopter flights were conducted to deploy sea ice buoys and search for penguins, seals (JvF) and whales (DT). On take off from the vessel the 10/10 ice coverage could be seen to include a network of leads and breathing holes similar to that reported in Thiele and Gill (1999). Two groups consisting of three undetermined minke whales were sighted on the survey routes mapped in Figure 3. Also depicted in this figure are the sightings of minke and probable minkes recorded on a visual survey along the cruise track whilst JvF conducted a helicopter survey ahead of the vessel. The helicopter survey recorded only one minke, while the ship based visual survey recorded 29 whales. These whales, either confirmed as minke whales, or as like minke whales, were spread evenly over the shelf area within 10/10 ice in depths generally less than 500m and in water temperature range of 2.1 - 2.2° C. Minke whale presence stopped abruptly once the swell affected region of ice was reached, coinciding with proximity to a steep section of shelf slope. On 27 April the vessel left the ice and headed back to the SO GLOBEC study site to resume line transect survey and sampling.
The IWC observer was provided with helicopter time to conduct two further whale flights whilst in the vicinity of Adelaide Island (Figure 4) and Anvers Island. The first of these surveys (1 May) covered a route from the vessel on the western side of Adelaide Island, around the southern coast and then north to Rothera Station. The helicopters then landed (to take equipment to Rothera). One helicopter was then used to conduct a survey of the area to the south of the station. Large numbers of humpback whales (20 in 10 pairs) were observed near Jenny Island, a location where we had previously biopsied a humpback pair on the US SO GLOBEC vessel Laurence M Gould (Figures 2 and 4). One pair of humpbacks observed on the helicopter flight was confirmed as a biopsied pair from the L M Gould cruise. Some minke whales were also observed on this flight, and a pair of humpbacks were seen feeding less than 1nm from the ship on the return flight.
The final helicopter survey was conducted on 2 May off Anvers Island to the north of the GLOBEC study site (near Palmer Station). On this short (due to adverse weather) flight we surveyed the south western bays of Anvers Island, observing pairs of humpbacks, and one group of four (with a large calf) close inshore in separate bays (Figure 2). The humpbacks appeared to be spread along these bays, and as this habitat extends to the north for some considerable distance, it is likely that many more groups inhabited the unsurveyed bays.
The areas of concentration of both minke and humpback whales sighted during the Polarstern survey coincide with those recorded later in the season from the Nathaniel B Palmer US SO GLOBEC cruise. On that cruise oceanographers determined that baleen whale distribution appeared correlated to the inshore cold Antarctic coastal current and intrusions of the Antarctic Circumpolar Current into Marguerite Bay (Wiebe et al. 2001).
Vessel and EK500 effects on baleen whales
Many minke and like minke whales were observed during the period when the Polarstern was within the sea ice to the south of Marguerite Bay (Figures 2 and 3). On both 23 and 24 April, groups and individual minke whales were observed throughout the day in close proximity to the vessel. Throughout this period the EK 500 echosounders were operating. The minke whales continually approached the vessel and remained nearby without appearing to be in any way disturbed by the echosounders or other activities around the vessel (other than to appear curious). On the 26th April, a clear sunny day within heavy ice, minke and like minke whales were observed many nautical miles ahead of the vessel in the ice. These whales were blowing consistently and maintained their position as the vessel approached and passed them. None were seen to move away from the vessel as it approached, although the echosounders were on, and would have been audible to them many miles from the ship. We would assume from this behaviour that the EK 500 echosounders do not significantly disturb the behaviour of these animals.
Thanks must go to the Captain and crew of the Polarstern, the cruise leader - Uli Bathmann, the Alfred-Wegener Institute, and to Jan van Franeker and Martin Doble for sharing their helicopter time with the IWC, sharing data and helping with mapping.
Pankow, H., Kock, K-H. 2000. Results of a sighting survey in the Antarctic Peninsula region in November - December 1996. SC/52/E23. Unpublished paper submitted to IWC SC 52.
Thiele, D., Gill, P. C. 1999. Cetacean observations during a winter voyage into Antarctic sea ice south of Australia. Antarctic Science 11 (1), 48-53.
Wiebe, P. et al. 2001. RVIB Nathaniel B. Palmer Cruise 01-03 to the Western Peninsula of Antarctica, US SO GLOBEC Report available on web site.
Related US SO GLOBEC reports:
LM Gould 01-03 1stcruise (mooring cruise) - US Southern Ocean GLOBEC Report No.1
NB Palmer 01-03 1stcruise (survey cruise)- US Southern Ocean GLOBEC Report No.2
LM Gould 01-04 2ndcruise (process cruise) - US Southern Ocean GLOBEC Report No.3
Web site for IWC cetacean summaries by cruise, cruise reports, and technical US SO GLOBEC reports:
this site provides a direct link to the CCPO site by clicking on SO
Table 1. Total cetacean sightings and number of animals in Antarctic
waters (south of 60° S) for
Polarstern AntXVIII5b 14 April - 7 May 2001
|Species - scientific name
|Species - common name
|Balaenoptera acutorostrata bonaerensis
|Minke (ordinary - dark shoulder)
|Like Balaenoptera acutorostrata
|Undientified large baleen whale
|Unidentified large baleen whale
|Unidentified large whale
|Unidentified large whale
|Undetermined Balaenoptera acutorostrata
|Undetermined minke whale
|Unidentified small baleen whale
|Unidentified small baleen whale
CLICK HERE FOR FIGURES IN WORD FORMAT