SC/53/E8

Deborah Thiele¹, Eileen Hofmann², Ari Friedlaender³, Sue Moore⁴, Mark McDonald⁵

¹Marine and Migratory Wildlife Ecology Group, School of Ecology and Environment, Deakin University, GPO Box 423, Warrnambool, Victoria, Australia 3280

²Center for Coastal Physical Oceanography, Crittenton Hall, Old Dominion University, Norfolk, VA 23529, USA

³Duke Marine Lab., Beaufort, North Carolina, USA

⁴NOAA/National Marine Fisheries Service, National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, Washington 98115, USA

⁵ 2535 Sky View Lane, Laramie, Wyoming82072, USA

Abstract

Note: all figures/maps are in colour and are available from the Secretariat as reference copies. A full set of images can be copied for individuals on request.

Introduction

At IWC 52 preparations were made for participation in the 2001 – 2002 ‘year round’ series of SO GLOBEC survey and process cruises. A budget was developed to include purchase of essential equipment; participation by Thiele (IWC-SO GLOBEC steering group Chair) in planning meetings and relevant GLOBEC workshops; and to fund IWC participation in the initial cruises planned for March – June 2001. Due to urgent funding requirements for the POLLUTION 2000+ initiative, it was agreed at IWC 52 that funds for the IWC-SO GLOBEC collaboration would need to be limited to equipment purchases and planning activities, with participation to be delayed until after IWC53 unless funds could be acquired outside the IWC SC budget. Thiele secured funding from the Australian Government to support initial IWC participation in the first three SO GLOBEC cruises. Equipment for the collaboration approved in the IWC 52 budget was purchased by the IWC.Items of equipment not covered in the IWC 52 budget were lent from Thiele’s SOCEP program. Although the opportunity to biopsy appeared unlikely prior to the initial cruises, we determined that it would be prudent to be prepared, and two sets of crossbows with associated biopsy sampling gear were kindly contributed by the Southwest Fisheries Science Center in return for any skin samples obtained. This meant that participation by the IWC could begin in the first phase of the program, and the opportunities provided by the substantial research effort in the first half of 2001 would not be lost.

A range of national research programs had been identified, some tentatively, to contribute to studies during 2001 – 2002 in the SO GLOBEC study area. However, by far the greatest effort came from the US National Science Foundation funded cruises. This effort includes five cruises in 2001 in the austral autumn and winter, all of which will be repeated at exactly the same time in 2002.

The overall goal of the US SO GLOBEC effort in this study is to elucidate shelf circulation processes and their effect on sea ice formation and Antarctic krill survivorship and availability to higher trophic levels, including seals, penguins and whales (Hofmann et al 2000 – draft plan in SC/52/E22 Appendix 1). The central Western Antarctic Peninsula (WAP) continental shelf area is characterised by unusually high krill production. The US SO GLOBEC research program structure has been developed around a central hypothesis: that a unique combination of physical and biological factors contribute to enhanced krill growth, reproduction, recruitment and survivorship throughout the year in the central Western Antarctic Peninsula (WAP) continental shelf area; and that in particular this region provides physical conditions that are especially favourable to winter survival of larval and adult krill.

The presence of krill predators in the study region, particularly in winter, is central to the main hypothesis of the research program. Seal and penguin studies are a strong component of the process study cruises in the US program. Clearly this program provided an unprecedented opportunity for the IWC to obtain data and conduct multidisciplinary analyses towards its objectives regarding associations between baleen whales, their prey and the physical environment. SO GLOBEC will benefit from the collaboration through an additional, and essential top predator component in their investigations of the dynamics of krill in these ecosystems.

Berths for IWC visual surveys were provided on the mooring cruise (L M Gould) and both survey cruises (NB Palmer) by the passive acoustic team led by John Hildebrand. The IWC team and this team have worked collaboratively throughout the US surveys. Process study cruises on the L M Gould run simultaneously with the N B Palmer survey cruises and although no berths were available for IWC on the LMG process cruises, the seal teams on board were trained to use Wincruz Antarctic by the IWC observers, and provided with equipment to record cetaceans whilst on watch. This approach further increased the cetacean coverage at a time of year when relatively few cetaceans are likely to be present.

Other national programs (ie.Germany,Brazil, UK) operating in the study region will contribute to the study by conducting complementary research in addition to the major US effort.

Here we:

1.Provide summaries from individual cruises on research conducted; 

2.Make recommendations for IWC participation and involvement in the SO GLOBEC analysis process. 

The SO GLOBEC study by the USA and other national programs in the MargueriteBay area of the Western Antarctic Peninsula (Figure 1.) commenced in March 2001. A range of cetacean research options were opportunistically pursued on each of these multidisciplinary cruises. Visual surveys were conducted on all cruises, passive acoustic studies were conducted (NSF Moore and McDonald) on the Gould and Palmer cruises; helicopter surveys were conducted from the Polarstern; and photo identification and biopsy sampling of minke and humpback whales was made possible from the Gould and Palmer cruises through the allocation of dedicated ship time for IWC studies by the US SO-GLOBEC program (five days on LMG and one day on NBP).

RV Laurence M Gould 18 March – 13 April

Methods – visual survey, biopsy and photo identification

Results – visual survey, biopsy and photo identification

Visual surveys alone were conducted from 19 March to 2 April during the oceanographic and acoustic mooring components of the cruise. Many humpback whales (Megaptera novaeangliae) were observed during the afternoon transit across the BransfieldStrait on 23 March. Five days of ship time were allocated to conduct cetacean survey (including closing on sightings, biopsy, photo identification and sonobuoy deployment) from first light on Tuesday 3 April to end of day Saturday 7 April. The weather improved markedly for this part of the survey. During this time the ship traversed the inside channels from the northern end of Renaud Island, Grandidier Channel, Crystal Sound, Matha Strait and passages to the east of Adelaide Island and the north-eastern section of Marguerite Bay (Figures 2 and 4). Figure 4.a, b show the Western Antarctic Peninsula and MargueriteBay study area with LMG 01-03 cetacean sightings.

Methods and sonobuoy recordings - passive acoustics

Given the great uncertainty in the numbers of blue whales in the Southern Ocean, and in the subspecies to which they belong, we believe the minimum census estimates which can be provided by acoustic monitoring is a key goal of the proposed project. Application of the techniques of point transect theory to the results of the survey where each acoustic contact is assigned a range should allow a minimum census estimate, the primary factor which will remain to be answered from other combined visual and acoustic data being the percent of whales calling during a time constant. The second fundamental goal of this work will be minimum population estimates and seasonal occurrence profiles for fin whales and humpback whales.Other species such as minke whales and sperm whales may be detected, but are expected to be so infrequent as to make population density estimates unreliable. Perhaps the most important overall result of this work will be to establish an acoustic detection baseline from which to measure future changes in relative abundance of Southern Ocean mysticete whales.

We deployed eight seafloor acoustic recorders (Figure 3.), each with a hydrophone thatis floated about 5 m above the seafloor.These instruments will record continuously at 500 samples per second for fifteen months, writing the data to 36 Gb of computer hard drive in each instrument.The recorders have a 16 bit dynamic range and are powered by lithium double D size batteries, which are placed inside high tensile aluminum pressure cases.The seafloor recorders use a system of drop weights, Benthos glass balls and an acoustic release for recovery. Throughout the cruise we deployed and recorded 36 directional sonobuoys and two broadband sonobuoys both randomly and when whales were sighted, as a means to record and thereby `groundtruth’ mysticete whale calls in this remote region. Recordings were obtained from humpback, minke and fin whales during the cruise.No blue or right whales were sighted or heard during this cruise.

General

Polarstern AntXVIII5b 14 April – 7 May 2001

The Polarstern departed on cruise AntXVIII5b on 14 April 2001 and headed directly for the SO GLOBEC study site (Figures 5. and 6.).

Most research work on the Polarstern has occurred in the Weddell Sea, however some research has been conducted in the WesternPeninsula and BellinghausenSea 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 the April – May cruise, 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 the helicopter surveys (which were conducted in good weather only) and on the one sunny day within the ice to the south of MargueriteBay. 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 N B Palmer. The ship remained working in the survey area until 21 April, and then steamed to the oceanic fast ice edge well to the south of MargueriteBay.

Figure 6. Polarstern AntVIII5b cruise track and inset of Figure 8&9 with all cetacean sightings. Species codes: 7=humpback – yellow circle; 13&59=Lagenorhynchus sp. – green diamond; 4,91&92=minke – black star; 9,64,65,67=unidentified whale – yellow triangle

Hourglass dolphins (1:10), like fin (1:2) and an unidentified whale were recorded in the transect area. 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. 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 Apriltwo 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 the usual 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 7. 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 and were spaced fairly evenly throughout. Minke whale presence stopped abruptly once the swell affected region of ice was reached, coinciding with the shelf break.

On 27 April the vessel left the ice and headed for the 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 AdelaideIsland (Figure 8.) and AnversIsland. The first of these surveys (1 May) covered an route from the vessel on the western side of AdelaideIsland, 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 JennyIsland, a location where we had previously biopsied a humpback pair from the L M Gould platform. 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 AnversIsland 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 AnversIsland, observing pairs of humpbacks, and one group of four (with a large calf) close inshore in separate bays. 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 coincide with those recorded on the N B Palmer cruise.

Nathaniel B. Palmer 01-03 24 April – 6 June

Methods – visual survey, photo identification and biopsy

Results – visual survey

Results – sonobuoy, photo identification and biopsy

On the evening of 24 May, sonobuoys recorded several humpback whales relatively close to the ship (C. Berchock pers. comm.), and whales were seen in the ship’s lights as the RVIB Nathaniel B. Palmer traveled north along the west coast of Alexander Island. At first light the ship was approximately 2 miles north of where the whales were seen. Ship’s time was dedicated to biopsy sampling for the day in the area where the whales were seen the previous day. At 0930 whales were sighted in an area with bands of brash ice several miles off the coast. Weather conditions were optimal for surveying and small boat work. In the area of the ship (68.75S, 71.35W) were 3 pairs of humpback whales and one single humpback whale, one group of 2 minke whales and one group of 3 minke whales. The whales appeared to be tracing back and forth, perpendicular to the coast in a 2-3 mile area. Photo-ID pictures were taken of each of the whales in the area, except 2 minkes and one humpback that were not approached. Video footage of the approach, biopsy shot and behaviour were taken. Biopsy samples were obtained from 3 humpback whales and 1 minke whale. Only one sample was taken from each group of animals approached. Skin samples were taken from all 4 whales, while blubber samples were taken from 2 of the humpbacks and the minke whale (Table 2).

General

A primary research objective of the cetacean studies within SO GLOBEC is to determine the winter distribution and foraging ecology of baleen whales in relation to the characteristics of the environment and the distribution of their prey. Sightings data from this cruise recorded only humpback (Megaptera novaeangliae) and minke (Balaenoptera acutorostrata) whales present in the study region in the austral fall and winter, suggesting that both over-winter around Marguerite Bay.Correlation of cetacean distributions with concurrent hydrographic distributions (Figures 9., 10., 11., 12.) show whales associated with: 1) the southern boundary of the Antarctic Circumpolar Current, 2) the frontal boundary between intrusions of warm Upper Circumpolar Deep Water and continental shelf water, and 3) the frontal boundary between inner shelf coastal current (Antarctic Coastal Current) and continental shelf waters (E. Hofmann pers. Comm., Figure 13.).Cetacean sightings were particularly numerous along the frontal boundary formed as the coastal current exits the southern end of MargueriteBay.Humpback whales were associated with all three frontal boundaries while minke whales were found only along the continental shelf and coastal frontal boundaries.The correspondence between the cetacean sightings and hydrographic features suggests that the austral winter distribution of cetaceans along the west Antarctic Peninsula is not random, but rather is determined by the structure of the physical environment, which in turn determines prey distribution.Continued analyses and collection of cetacean sightings data in conjunction with concurrent prey and hydrographic distributions will allow determination of the causal relationships underlying austral winter cetacean distributions in the Antarctic Peninsula region. This survey cruise included a comprehensive suite of physical and biological programs and an extensive range of scientific equipment in order to carry out both fine and larger scale studies (ie. biomapper, ctd, echosounders, net sampling, ROV, primary productivity etc..). It is one of the most comprehensive multidisciplinary cruises ever conducted in the Southern Ocean and provides the IWC with access to a well planned cruise and analysis process of enormous scope and potential.

Preliminary results from NB Palmer 01-03 on adult krill distribution and migration in Antarctic autumn with implications for baleen whale winter strategies and feeding ecology

One of the major objectives of all krill related studies in the Southern Ocean has involved the determination of over wintering strategies for this species which at present are unknown. In 1986 Kawaguchi et al. suggested that krill were benthopelagic animals which probably migrated to the sea floor during autumn and winter. However, they had no quantitative data to support this hypothesis. Siegel and Kalinowski (1994) speculated on a seasonal migration of krill across shelf areas, with this autumn/winter migration possible related to the food gradient across the shelf (ie. that benthic food sources may be the key to overwinter survival). Later, Gutt and Siegel (1994) reported benthopelagic krill aggregations at the shelf edge in the southeastern Weddell Sea which they observed directly along transects using a video camera mounted on a ROV. The observations were made at depths of 480 and 416m from a distance of up to 200cm above the bottom. At one station a swarm was observed to reach densities of several tens to several hundreds of specimens per m3, maximum density exceeded 230 specimens per m3.

was then followed up by observations by Gutt and Siegel (1994).

During the N B Palmer survey cruise (and on Polarstern line transects) predominantly larval krill were found on the outer shelf and oceanic regions of the study area. Adult krill were for the most part only observed in near-shore shoal areas with widely varying (complex) topography (refer to Fig 28.US SO GLOBEC Technical Report #2, Wiebe et al. 2001). Basically the adult krill were observed aggregated in holes among the peaks in a complex sea floor. These areas of krill concentration occurred off the northern portion of AlexanderIsland and the southern end of AdelaideIsland. These coincide with baleen whale concentration sites recorded in autumn and early winter on the 2001 cruises. The presence of aggregations of adult krill inshore from the shelf is interesting because, if this autumn – winter pattern is shown to be widespread in MargueriteBay and similar areas, then an overwinter food source is potentially available to baleen whales. In the past it has been reported that all baleen whales (except minkes as reported in Thiele and Gill, 1999) migrated out of the Antarctic once the summer ‘feeding’ season ended. The July to September 2001 winter survey by the N B Palmer (NBP 01-04) and data from the passive acoustic moorings will help determine whether baleen whales remain in this region of the Antarctic; whether they are feeding during the autumn and winter; and what prey they are consuming. It may well be that while the majority of baleen whales depart the rich Antarctic feeding grounds in early autumn, in some areas some portion of populations of baleen whales may remain throughout the winter, supported by adult krill concentrations which appear to be located in direct association with well defined oceanographic and bathymetric features.

Acknowledgements

References

Franklin, J. F., Bledsoe, C. S., Callahan, J. T. 1990. Contributions of the Long-Term Ecological Research Program. Bioscience 40 (7): 509 – 523.

Gutt, J. , Siegel, V. 1994. Benthopelagic aggregations of krill on the deeper shelf of theWeddell Sea (Antarctic) Deep Sea Research I Vol 41 No. 1: 169 – 178.

Haskell, A. G. E., Hofmann, E. E., Klinck, J. M., Lascara, C. M. 2001. Lagrangian modeling studies of the spatial dynamics of Antarctic krill (Euphausia superba). Submitted to Journal of Marine Research April 2001.

Hofmann, E. E., Klinck, J. M., Lascara, C. M., Smith, D. A. 1996. Water mass distribution and circulation west of the Antarctic Peninsula and including BransfieldStrait. Foundations for Ecological Research West of the Antarctic Peninsula, Antarctic Research Series 70: 61 – 80.

Hofmann, E. E., Lascara, C. M. 2000.Modeling the growth dynamics of Antarctic krill Euphausia superba. Marine Ecology Progress Series 194: 219 – 231.

Hofmann, E. E., Reilly, S. 2000. An invitation for the IWC to participate in Southern Ocean GLOBEC.SC/52/E22. Unpublished paper submitted to IWC SC 52.

Kawaguchi, K., Matsuda, O., Ishikawa, S., Naito, Y. 1986.The overwintering strategy of Antarctic krill under the coastal fast ice off the OngulIsland in Lutzow-HolmBay, Antarctica.Memoirs of the National Institute of Polar Research Tokyo Special Issue 44: 67-85.

Limeburner, D. et al. 2001. RV Laurence M Gould Cruise 0103 to the Western Peninsula of Antarctica US SO GLOBEC Report available on web site.

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.

Prezelin, B. B., Hofmann, E. E., Mengelt, C., Klinck, J. M. 2000. The linkage between Upper Circumpolar Deep Water (UCDW) and phytoplankton assemblages on the west Antarctic Peninsula continental shelf. Journal of Marine Research 58: 165 – 202.

Reilly, S., Hedley, S., Hewitt, R., Leaper, R., Thiele, D., Pitman, R. L., Naganobu, M., Watkins, J., Holland, R. 2000. SOWER 2000: initial results from the IWC-CCAMLR program to study whales and krill in the Southern Ocean. unpublished paper submitted to IWCSC 52.International Whaling Commission Scientific Committee June 2000, Adelaide, SC/52/E21.

Siegel, V., Kalinowski, J. 1994 in Southern Ocean Ecology: The Biomass Perspective. El-Sayed, S. Z. (ed.) CambridgeUniversity Press.

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.

Thiele, D., Chester, E. T. 2000. Ecological research and baleen whale management: a case study from the Southern Ocean. Unpublished paper submitted to the International Whaling Commission Scientific Committee June 2000, Adelaide, SC/52/E9.

Wiebe, P. et al. 2001. RVIB Nathaniel B. Palmer Cruise 0103 to the Western Peninsula of Antarctica US SO GLOBEC Report available on web site.

Reports:

LMGould 01-03 1^stcruise (mooring cruise) - US Southern Ocean GLOBEC Report No.1

NBPalmer 01-03 1^stcruise(survey cruise)- US Southern Ocean GLOBEC Report No.2

LMGould 01-04 2^ndcruise (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:

http://www1.npm.ac.uk/globec/this site provides a direct link to the CCPO site by clicking on SO GLOBEC

Table 1. Total cetacean sightings and number of animals in Antarctic waters (south of 60°S) for 2001 SO GLOBEC cruisesLMG 01-03 18 March – 13 April 2001, Polarstern AntXVIII5b 14 April – 7 May 2001, and NBP 01-03 24 April – 6 June

Table 2. Cetacean biopsy samples LMG 01-03 and NBP 01-03 cruises

 

Date	3 April 2001	4 April 2001	4 April 2001	5 April 2001	7 April 2001	25 May 2001	25 May 2001	25 May 2001	25 May 2001
Latitude (S)	66 02.15	66 40.41	66 41.38	67 42.90	65 34.44	68.75	68.75	68.75	68.75
Longitude (W)	65 46.27	67 24.53	67 26.27	68 09.19	64 54.99	71.35	71.35	71.35	71.35
Unique Id (WS#)	LMG 01-03#51	LMG 01-03#57	LMG 01-03#60	LMG 01-03#73 A + B	LMG 01-03#85 A + B	NBP 01-03#34	NBP 01-03#35	NBP 01-03#37	NBP 01-03#36
Species	2	1	1	2	2	2	2	2	1
Group size	2	7	50	2	2	2	2	2	3
No. animals sampled	1	1	4	2	2	1	1	1	1
photo id	Y	Y of group	Y of group	Y	Y	Y	Y	Y	Y

Species 1 = minke dark shoulder form

Species 2 = humpback