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Keywords:

  • Antarctic blue whales;
  • Balaenoptera musculus brevicauda;
  • Balaenoptera musculus indica;
  • Balaenoptera musculus intermedia;
  • distribution;
  • pygmy blue whales;
  • true blue whales;
  • whaling

ABSTRACT

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGEMENTS
  8. REFERENCES
  9. Appendices
  • 1
    Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303 239), sightings (4383 records of ≥8058 whales), strandings (103), Discovery marks (2191) and recoveries (95), and acoustic recordings.
  • 2
    Sighting surveys included 7 480 450 km of effort plus 14 676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar.
  • 3
    Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering.
  • 4
    Compared with historical catches, the Antarctic (‘true’) subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic.
  • 5
    Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales.
  • 6
    South-east Pacific blue whales have a discrete distribution and high sighting rates compared with the Antarctic. Further work is needed to clarify their subspecific status given their distinctive genetics, acoustics and length frequencies.
  • 7
    Antarctic blue whales numbered 1700 (95% Bayesian interval 860–2900) in 1996 (less than 1% of original levels), but are increasing at 7.3% per annum (95% Bayesian interval 1.4–11.6%). The status of other populations in the Southern Hemisphere and northern Indian Ocean is unknown because few abundance estimates are available, but higher recent sighting rates suggest that they are less depleted than Antarctic blue whales.

INTRODUCTION

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGEMENTS
  8. REFERENCES
  9. Appendices

The blue whale Balaenoptera musculus is the largest of the mysticete (baleen) whales, with lengths exceeding 30 m. It was once abundant in the Southern Hemisphere, but was subject to intensive exploitation by whaling beginning in 1904 (Branch, Matsuoka & Miyashita, 2004); this was particularly true in the Antarctic, where blue whales congregated in summer to feed, primarily on krill Euphausia superba.

Despite being the largest animals ever to exist on Earth, surprisingly little is known about the distribution and migration of blue whales in the Southern Hemisphere and northern Indian Ocean. In this region, there are two recognized subspecies, the Antarctic (or true) blue whale B. m. intermedia and the pygmy blue whale B. m. brevicauda (Rice, 1998). Compared with pygmy blue whales, Antarctic blue whales attain greater maximum lengths (>30 m vs. 24.1 m), are longer at sexual maturity (23.7 m vs. 19.2 m) and have proportionately longer tail regions (Mackintosh & Wheeler, 1929; Ichihara, 1966). In the austral summer, Antarctic blue whales are generally found south of 55°S while pygmy blue whales are generally believed to remain north of 54°S (Ichihara, 1966; Kato, Miyashita & Shimada, 1995). Based on a combination of evidence from three long-term sightings series, Antarctic blue whales were depleted to very low levels before increasing to 1700 (95% Bayesian interval 860–2900) in 1996, but remain at less than 1% of their original abundance of 239 000 (95% Bayesian interval 202 000–311 000) (Branch et al., 2004). The status of pygmy blue whales is much more uncertain but their original abundance was probably an order of magnitude lower than that of Antarctic blue whales, and they are likely less depleted at present.

The distribution of blue whales in the Southern Hemisphere and northern Indian Ocean is poorly understood, except perhaps for the Antarctic during the austral summer. Some previous studies have assumed that they are distributed throughout this region (e.g. Gambell, 1979; Mizroch, Rice & Breiwick, 1984), presuming that gaps in their distribution are caused by lack of search and catch effort rather than a true absence of blue whales. However, data from Japanese Scouting Vessels (JSV, 1965–87) show that despite widespread effort, sightings were concentrated in the South Indian Ocean and largely absent from the South Pacific and South Atlantic Oceans (Miyashita, Kato & Kasuya, 1995). Plots interpolated from catches (Mikhalev, 2000; Best et al., 2003) are revealing but ignore information from sightings, strandings and acoustic detections. The best effort at drawing together data from different sources is that of Yochem & Leatherwood (1985), but their map did not include subsequent revelations of widespread illegal Soviet catches in the 1960s and 1970s (Yablokov, 1994; Mikhalev, 1997a; Yablokov et al., 1998); it also interpolated between rare catches in some regions, and contained many question marks over the distribution of blue whales in other areas.

The classic theory of migration patterns for blue whales may also be in need of revision. It has long been assumed that Antarctic blue whales migrate to temperate mating and calving areas in the winter and then return to the Antarctic to feed in the summer. Early work by Mackintosh & Wheeler (1929) showed conclusively that the whales caught at South Georgia and at Saldanha Bay, South Africa, were morphologically similar, and that the timing of catches at the two locations was consistent with migration. Year-round voyages of the Discovery II showed a marked rise and fall of baleen whale numbers in the Antarctic also consistent with migration (Mackintosh, 1966). Finally, there is unequivocal evidence for this migration pattern in humpback whales Megaptera novaeangliae and some indications of a similar migration in fin whales Balaenoptera physalus; thus, it has been argued by analogy that the pattern holds also for blue whales (Mackintosh & Wheeler, 1929; Mackintosh, 1966).

More recent analyses of length frequencies (based on a database containing 82% of all catches between 1914 and 1973) have reinforced the conclusion that Antarctic blue whales migrate to South African and Namibian waters in winter (Best, 1998; Branch et al., 2007). Additionally, acoustic recordings (from the 1990s onwards) have detected brief periods of Antarctic-type calls in the austral autumn and winter (peaking in July) in the eastern tropical Pacific and central Indian Ocean, and off south-west Australia and northern New Zealand (Stafford et al., 2004; McDonald, 2006).

However, not all evidence supports the migration hypothesis: some Antarctic blue whales remain behind during the winter. At South Georgia, blue whales were present year-round (Hinton, 1915; Risting, 1928). There were also year-round acoustic detections of blue whales in the West Antarctic Peninsula (Širovićet al., 2004) and East Antarctic (McKay, Širović & Thiele, 2005), although these were greatly reduced in winter.

It is also well-known that pygmy blue whales do not generally migrate to the Antarctic in summer. Pygmy blue whales in the northern Indian Ocean form a resident population (Yochem & Leatherwood, 1985; Mikhalev, 2000; Anderson, 2005), and the abundance of pygmy blue whales around Australia (Gill, 2002), south of Madagascar (Best et al., 2003) and in the southern Indian Ocean (Zemsky & Sazhinov, 1982; Miyashita et al., 1995) peaks in the summer months. Blue whale catches and sightings in the south-east Pacific are also more common in summer than in winter (Clarke, Aguayo & Basulto, 1978; Hucke-Gaete et al., 2003).

To provide updated maps of blue whale distribution, to address questions about the classical migration theory for blue whales and to compare densities in different regions, we compiled available data for catches, sightings, strandings, acoustic recordings and Discovery mark recoveries from a variety of published and unpublished sources. The resulting data were compared with maps of bathymetry, thermal fronts and phytoplankton biomass to better understand their association with blue whale distribution. Finally, the whale data were examined for monthly patterns suggesting migration.

METHODS

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGEMENTS
  8. REFERENCES
  9. Appendices

The study area is defined to be the entire Southern Hemisphere in addition to the northern Indian Ocean, because this covers the known distribution of Antarctic and pygmy blue whales. In the eastern tropical Pacific, sightings between the equator and 5°N are also included, because extensive surveys there (e.g. Reilly & Thayer, 1990) show that there is a gap (∼3–7°N) between blue whale sightings near the Costa Rica Dome that are from the California/Mexico population (Mate, Lagerquist & Calambokidis, 1999), and those closer to the equator that probably come from the south-east Pacific population. Data were collected on bathymetry, thermal fronts and phytoplankton biomass to relate these environmental factors to blue whale distribution. The study focused on positional information from catches, sightings, strandings, mark-recaptures (using Discovery marks) and acoustic detections, but did not include data from several satellite tagging and photo-identification studies since these had not yet been published. Positional data were separated into whaling (≤1973) and post-whaling (>1973) eras to assess whether the occurrence and distribution of blue whales was affected by whaling.

Historical catches

Catch positions were provided by the International Whaling Commission (IWC) Secretariat and include an up-to-date account of catches by the USSR in the 1950s to 1970s, correcting for USSR misreporting and illegal whaling (Yablokov, 1994; Mikhalev, 1997a; Yablokov et al., 1998). Catch positions were recorded to the nearest degree for many earlier catches, but to the nearest minute for later catches. The positions associated with land station catches were usually fixed and did not represent the actual catch positions, except in later years. Finally, the catch database does not have a fully comprehensive set of individual positions, especially for the early part of the 20th century and during World Wars I and II.

Nearly all whaling on blue whales was conducted in the Antarctic, providing little information on blue whale distribution outside this area. However, Soviet vessels travelled widely outside the Antarctic during the 1950s to 1973, catching whales without regard to closed seasons, closed areas and forbidden species. Revised data on their catches are available from 1958 to 1973. For this period of time, a proxy of Soviet effort was obtained by comparing the catches of blue whales with those of all whales for each 2° × 2° square.

Sightings

Sightings were obtained from a wide variety of published papers, technical reports and unpublished IWC Scientific Committee documents, in addition to unpublished data from the authors of this paper and other sources listed in the acknowledgements (Appendix 2). Potential sources were restricted to a manageable number by including only sources that listed blue whale sightings. Because effort associated with surveys with zero sightings was excluded, total estimated effort is negatively biased. Where the number of groups of whales was recorded, this may have referred to schools (stable groups of whales that usually travel together and are often related) or to feeding aggregations (unstable groups aggregating around an ephemeral food source). Where later papers referred to the same sightings obtained from another more primary source, the earlier source was preferred. Less effort was expended in collating sightings prior to 1973 while catches were still being taken. For example, no effort was made to extract data from logbooks of 19th century American whaling boats except for those collated by Wray & Martin (1983). Four particularly extensive datasets are described in more detail below.

IDCR/SOWER database

Antarctic surveys were conducted under the auspices of the IWC from 1978/79 to 2005/06, under the auspices of the International Decade of Cetacean Research (IDCR), and Southern Ocean Whale and Ecosystem Research (SOWER) programmes (Branch & Butterworth, 2001a; Matsuoka et al., 2003). Sightings were obtained from the IWC's database DESS 3.42 (Database-Estimation Software System, Strindberg & Burt, 2004) for 1978/79–2004/05. Details from each survey can be obtained from the individual cruise reports (e.g. Ensor et al., 1999, 2000, 2004). At the time of submission, sightings had not been encoded from the 2005/06 survey (33 groups, 63 whales) (Ensor et al., 2006).

JARPA database

The Japanese Whale Research Program under Special Permit in the Antarctic (JARPA) has so far operated from 1989/90 to 2005/06. Blue whale abundance estimates have beencalculated up to the 2004/05 season (Matsuoka et al., 2006), and sightings from 1989/90 to 2004/05 are included in this paper. Effort was widespread south of 60°S and from 35°E eastwards to 145°W. Additional effort was recorded in much of the region north of 60°S during transits and during surveys between 57°S and 60°S.

JSV database

Japanese Scouting Vessels (JSV) recorded noon-day positions, total blue whales sighted on that day, and daily search effort from 1965/66 to 1988/89 (Miyashita, Shigemune & Kato, 1994; Miyashita et al., 1995). However, from the 1978/79 season onwards, some of these vessels were also used in the IDCR/SOWER surveys, resulting in potential record duplication in the two databases. Since the IDCR/SOWER records contained more accurate positions these were preferred, reducing JSV records from 2520 blue whales (recorded on 833 vessel-days) to 2410 whales (799 vessel-days). JSV recorded the number of groups and number of whales in most years, but in some years the number of groups was not recorded.

SWFSC surveys in the eastern tropical Pacific

The Southwest Fisheries Science Center (SWFSC) of the U.S. National Marine Fisheries Service conducted a series of marine mammal surveys in the eastern tropical Pacific between 1986 and 2006 (e.g. Holt & Sexton, 1987; Hill, Rasmussen & Gerrodette, 1991; Mangels & Gerrodette, 1994; Kinzey et al., 2001; Jackson et al., 2004). The surveys extended eastwards from Hawaii to California and Mexico and southwards to about 15°S. Previous blue whale sightings around the Costa Rica Dome (Wade & Friedrichsen, 1979; Reilly & Thayer, 1990) have been linked through satellite tagging to the Mexico/California population of northern blue whales, B. m. musculus (Mate et al., 1999). For this reason, only the effort and sightings south of 5°N were included in this study, as these sightings were considered more likely to be from the south-east Pacific grouping of blue whales.

Effort assessment

Where reported, the effort associated with each survey was recorded. Where multiple surveys were conducted in a study, the total effort for all surveys was reported even if blue whales were not sighted on many individual surveys. However, the effort associated with a very large number of studies that reported zero blue whale sightings was excluded. Effort was reported in a variety of ways: days, hours, kilometres or nautical miles. The total effort was estimated by assuming that 10 hours of effort equalled 1 day and by converting measurements from nautical miles to kilometres. For sighting rates, where the number of groups was not consistently recorded (e.g. JSV), the number of whales was converted to number of groups using the mean group size from all other records.

Strandings

‘Strandings’ included both live strandings and washed up and floating carcasses. Sources (listed in Appendix 3) included published and unpublished reports, and relied heavily upon previous collations of sightings, e.g. James & Soundararajan (1979), De Silva (1987) and Sathasivam (2000). Identification was usually clear, as evidenced by a published description by a cetacean expert, a maximum length exceeding that of other species in the region, completely black baleen plates or other diagnostic features. Reports identified as B. indica (originating from Blyth, 1859) (the Great Indian Fin Whale or Great Indian Rorqual) were considered to be a synonym for B. musculus (Rice, 1998). Although care was taken to include only strandings verified to be blue whales, in many cases, particularly in the northern Indian Ocean, the published descriptions did not provide full details of how the species identification was made. Original records of older strandings could not always be obtained as they were often published in obscure and inaccessible journals. In such cases, the closest summary in time was used and the oldest known reference noted. The reliability of length measurements varies. Older records probably measured maximum total length which is appreciably longer than the accepted standard catch measurement from the ‘tip of the snout to the notch of the tail flukes’ (Mackintosh & Wheeler, 1929); thus, older measurements are probably biased high. In the majority of cases, the name of the stranding location was given but not the exact latitude and longitude. In these cases, the place was located using Google Earth software (http://www.earth.google.com) to find the most accurate position. This was particularly difficult for Indian place names where variant spellings and name changes were common.

Mark-recaptures and movements

The only source of mark-recapture data included in this paper are Discovery marks, but a brief outline of known work on photo-identification and satellite tags is summarized at the end of this section.

Mark and recapture data from the Discovery marking program and the International Marking Scheme were obtained from the IWC Secretariat and are listed in Appendix 4. Marks consisted of a metal tube stamped with a unique serial number that was fired into the muscle of the whales, and recovered during whaling (Brown, 1954, 1962). The mark-recaptures included three (no. 25601, no. 25608, no. 25619) from Soviet expeditions (Mikhalev & Tormosov, 1997) not currently in the IWC database, and excluded German mark G00706, which had a missing recapture location. There is some doubt about the mark positions and species identity (fin or blue whale) of Soviet marks no. 1294 and no. 1298 reported in Ivashin (1971); thus, these were excluded. There were nine instances where two marks were recaptured from a single whale. In each instance, both marks had been placed on the same day and almost identical location; thus, the numerically higher mark was excluded from analyses of the Discovery marks.

Photo-identification studies include those from Sri Lanka (Alling, Dorsey & Gordon, 1991), and studies in progress in Perth Canyon in Western Australia (K. C. S. Jenner, M.-N. M. Jenner & V. J. Sturrock, unpublished data), Bonney Upwelling, southern Australia (P. C. Gill & M. G. Morrice, unpublished data), Geographe Bay, Western Australia (C. Burton, unpublished data), Chile (Hucke-Gaete, Viddi & Bello, 2005; Cabrera et al., 2006), Indonesia (B. Kahn, unpublished data) and the Southern Ocean (P. Olson, personal communication).

Satellite tagging has been conducted around Australia (N. Gales, K. C. S. Jenner & P. C. Gill, unpublished data), Indonesia (Kahn, 2005) and Chile (Hucke-Gaete et al., 2005).

Acoustic detections

Acoustic recordings of Southern Hemisphere blue whales were obtained from a variety of sources based on bottom-moored or sound channel-moored hydrophones, dipping hydrophones and sonobuoys (Appendix 5). Sonobuoys record data over relatively short time frames (hours), whereas moored hydrophones are capable of collecting year-round datasets. Sonobuoys were deployed during seven SOWER cruises (1996–2006) both in the Antarctic and in pygmy blue whale habitat during the austral summer. The distance at which calls can be detected depends on many factors including bottom topography type, ambient noise levels, instrument type, and depth of the vocalizing whale and receiver. Since these factors were seldom recorded in our sources, it is generally not possible to estimate how far away the calling whales were. Širović (2006) does estimate that Antarctic-type calls from the Antarctic Peninsula were detected up to 200 km away from bottom-mounted instruments in October and November, but we believe the distance to be much less for most of the other studies cited.

Reliability of data

The catch database covers 83.6% of known catches of blue whales in the study area. Similarly, the set of mark-recaptures examined is comprehensive and differs little from previous extensive analyses (Rayner, 1940; Brown, 1954, 1962). Strandings are more commonly reported from areas of high human population density and where there are cetacean experts, which explains why strandings were reported in such high numbers from India, Sri Lanka, Australia, New Zealand and Chile. The absence of any strandings around Africa, despite high catches from the south-west coast, is at least partly due to low monitoring effort. The sightings data were often from surveys in restricted areas, except for major efforts like JSV, JARPA and IDCR/SOWER. Many areas were never surveyed while other areas were intensively studied. Since sighting effort was not included from publications recording zero blue whales, the study-wide sighting rate estimate will be biased high. Finally, sighting rates are obviously difficult to compare from one study to another because the sighting platform, number of observers, vessel speed, sighting conditions and many other factors vary. Nevertheless, blue whales produce highly visible and relatively frequent blows so that we assumed that sighting rates varying by an order of magnitude or more would reflect real differences in densities. Acoustic data provide reliable presence-absence information but were often obtained incidental to other studies and did not include concurrent visual sightings of blue whales. Although relative densities can be inferred from the number of calls recorded, it is unknown what proportion of blue whales produces calls and therefore acoustic data cannot be used to estimate the number of individuals in range of the acoustic instrument.

Bathymetry, thermal fronts and phytoplankton chlorophyll-a concentrations

To better understand the possible environmental correlates of blue whale distribution, large-scale positions of bathymetry, thermal fronts and phytoplankton biomass were obtained from digital sources. Bathymetry for the study area was obtained from version 8.2 (November 2000) of the dataset described in Smith & Sandwell (1997), and was downloaded from the website of the Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography (http://topex.ucsc.edu/). These data come from a combination of depth soundings and satellite gravity measurements and have a nominal resolution of about 4 km.

Following the representation of Moore & Abbott (2000), we obtained the mean annual position of the major fronts in the Southern Ocean. These include, from north to south: the North Subtropical Front, the Agulhas Current Front, the South Subtropical Front, the Subantarctic Front, the Southern Antarctic Circumpolar Current Front, and the Antarctic Polar Front. For the more northern regions, we considered the annual mean location of the Costa Rica Dome in the eastern tropical Pacific (∼9°N 90°W), as outlined by the 20°C isotherm depth at 35 m (Fiedler, 2002), and the location of the 25°C isotherm at the surface, which marks the position of the seasonal Equatorial Front in the eastern equatorial Pacific and eastern equatorial Atlantic. The surface manifestation of the 25°C isotherm also describes the extent of south-west monsoon-induced upwelling in the western Indian Ocean. The mean position of the 25°C isotherm was obtained from a satellite-derived sea-surface temperature climatology for the month of August from NOAA's National Oceanographic Data Center (http://www.nodc.noaa.gov/sog/pathfinder4km/) (sensor: AVHRR, grid resolution: 4 km, base period: 1985–2001; see Casey & Cornillon (1999) for details of an earlier version of this product).

Long-term annual and seasonal mean phytoplankton chlorophyll-a concentrations, a proxy for biomass, were obtained in mg.m−3 from satellite measurements (sensor: SeaWiFS, grid resolution: 9 km, base period: 4 September 1997 to 30 September 2006; http://oceancolor.gsfc.nasa.gov/). One caveat is that these measurements are from surface waters and may not reflect phytoplankton biomass associated with the deep chlorophyll maximum.

RESULTS

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGEMENTS
  8. REFERENCES
  9. Appendices

Catches

The IWC catch database includes catch positions for 303 329 blue whales (and individual data for 311 948 whales in all) in the study area, i.e. 83.6% of the estimated 362 879 blue whales caught in this region (Branch et al., 2004). Figure 1 shows the distribution of the catch and the major environmental features of the study area, although treatment of the association between the latter and blue whale distribution is left for the Discussion section. Catches covered the Antarctic densely. The major concentrations of catches in the Antarctic shifted southwards from October–December to January–March (Fig. 2). In the South Pacific, there were widespread catches along the west coast of South America north of 44°S off Chile, Peru and Ecuador and from Peru to the Galapagos Islands, but no other catches north of 59°S in the waters stretching west to 180°. In the South Atlantic, there were isolated catches off Argentina, Uruguay and Brazil. However, the identification of one of the two Brazilian catches is questionable given that it was recorded as either a ‘bowhead or blue’ whale, neither of which is very likely. There were substantial catches off Angola, Namibia and the west coast of South Africa and a single catch off Congo. Catches were common off Durban (South Africa), from south of Madagascar to Australia, around the south and west coasts of mainland Australia and Tasmania, in the north-western Indian Ocean, and north-west of New Zealand. Pelagic catches in the Indian Ocean were limited to the 1959/60–1963/64 Japanese expeditions and 1962/63–1972/73 USSR expeditions capitalizing on the discovery of pygmy blue whales (Ichihara, 1961).

image

Figure 1. (a) Bathymetry and mean location of major oceanographic features in the study area (see text for details). From north to south: CRD, Costa Rica Dome; EF, Equatorial Front; NSTF, North Subtropical Front; AgCF, Agulhas Current Front; SSTF, South Subtropical Front; SAF, Subantarctic Front; APF, Antarctic Polar Front; SACCF, Southern Antarctic Circumpolar Current Front. (b) Annual mean phytoplankton chlorophyll-a concentrations in mg.m−3 from SeaWiFS (4 September 1997–30 September 2006). (c) Catches of blue whales in the International Whaling Commission database grouped into 1° × 1° squares. Catches from land stations were generally all assigned to the same square.

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image

Figure 2. Three-monthly seasonal patterns in catches (grouped into 1° × 1° squares) and mean seasonal phytoplankton chlorophyll-a concentrations in mg.m−3. Sources are the same as Fig. 1.

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The pattern of Soviet catches (1958–73) of all large cetacean species is revealing (Fig. 3). In some areas, Soviet blue whale catches were very scarce despite considerable catches of other large cetaceans, particularly in the South Atlantic, central Indian Ocean, south of South America and in the Tasman Sea.

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Figure 3. Soviet catches during 1958–73 in the study area. Top panel: number of catches of all large cetaceans in each 2° × 2° square (a rough measure of total catch effort). Bottom panel: proportion of large cetacean catches in each 2° × 2° square that were blue whales.

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Sightings

The sightings database included 4383 records comprising at least 8058 individual whales (Appendix 2), of which 3691 records of at least 6019 whales were recorded after 1973. Sightings largely mirrored the catch distribution, except for scattered sightings in the South Pacific and South Atlantic, broad areas south and south-west of Australia, in Indonesia and north of New Zealand to the equator (Fig. 4). In the Antarctic, all sightings were clustered close to the continent in a much more restricted range than the catches. Where individual group sizes were recorded (n = 3346; mean = 1.56; S.E. = 0.026; range = 1–60), the great majority comprised one (65.2%) or two whales (24.6%), and groups exceeding five whales were rare (1.1%) (Table 1). The total estimated effort where recorded was ∼14 676 days (624 groups) plus ∼7 480 450 km (3365 groups). Overall sighting rates were therefore approximately 0.04 per day or 0.45 per 1000 km (one group every 2200 km), but are obviously biased upwards because most studies focused on high-density blue whale areas and many studies that reported no blue whales were excluded. For large-scale surveys with dedicated cetacean effort and good sighting platforms, sighting rates varied by more than four orders of magnitude from region to region. When ordered, these sighting rates (groups per 1000 km) are as follows: off Costinha, Brazil, 0.003 (da Rocha, 1983); off Durban, South Africa, 0.005 from spotter planes (P. B. Best, unpublished data); around Somalia, 0.19 (Small & Small, 1991); around the Galapagos Islands, 0.25 (Palacios, 1999a); Oman, 0.32 (Oman Whale and Dolphin Group, unpublished data); Antarctica south of 55°S, 0.17 (JSV), 0.34 (JARPA, Matsuoka et al., 2006) and 0.52 (IDCR/SOWER); South Georgia, 0.44 (Moore et al., 1999); in the eastern tropical Pacific, 0.45 (SWFSC surveys); off Peru, 0.73 (Donovan, 1984a) and 0.97 (Valdivia et al., 1983; Ramirez, 1985); around Komodo and Solor-Alor, Indonesia, 2.0 (Kahn, 2000, 2002, 2005; B. Kahn, unpublished data); Maldives, 2.4 (Ballance et al., 2001); southern Indian Ocean 35–50°S 30–100°E, 2.9 (JSV); east Sri Lanka, ∼6 assuming vessel speed of 5 knots (Alling et al., 1991) and north-west Sri Lanka, 1.6 (A. D. Ilangakoon, unpublished data); off southern Australia, 7.4 (Gill, 2002; P. C. Gill & M. G. Morrice, unpublished data); off western Australia, 18.5 (K. C. S. Jenner, M.-N. M. Jenner & V. J. Sturrock, unpublished data) and 18.6 (J. L. Bannister & C. L. K. Burton, unpublished data); on the Madagascar Plateau, 36.0 (Best et al., 2003); and off Chile, 4.9 from a ship survey (Findlay et al., 1998) and 52.4 from aerial surveys north-west of Chiloé Island (Galletti Vernazzani, Carlson & Cabrera, 2005; Galletti Vernazzani et al., 2006).

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Figure 4. Positional information from (top to bottom) sightings (○); strandings (▵); and acoustic recordings (□). Grey is used for positions ≤1973 and black for >1973. Acoustic locations are annotated with the call type using numbers: Antarctic (1), South-east Pacific (2), New Zealand (3), Sri Lanka (4), Australia (5) and Madagascar (6); these numbers are concatenated if two or more call types were recorded at a single location.

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Table 1.  Distribution of group sizes in sightings data, based on reports where group sizes were recorded. Groups may have been either schools or feeding aggregations, depending on the source. The largest groups were 10, 12, 15, 18, 20 and 60.
Group sizeFrequencyPercentage
1218365.2
282224.6
32056.1
4621.9
5371.1
6150.4
760.2
860.2
940.1
≥1060.2
Total3346100.0

Nearly all of the sightings on the IDCR/SOWER surveys were near the southern boundary of the survey region despite substantial effort northwards of the pack ice to 60°S (Fig. 5). Furthermore, during transits to the Antarctic, sightings were recorded only in the southern Indian Ocean, and never during transits south of South Africa, South America, Tasmania, or New Zealand despite substantial search effort.

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Figure 5. IDCR/SOWER vessel tracks (lines) and blue whale sightings (○) between 1978 and 2005. Only primary search effort is plotted, but blue whales sighted both on-effort and off-effort are plotted. The intended surveys were generally conducted south of 60°S (dashed line) but additional primary effort was recorded further north during transits to the survey areas. IDCR, International Decade of Cetacean Research; SOWER, Southern Ocean Whale and Ecosystem Research.

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The JSV database included 4 827 370 km of search effort throughout the study region (Fig. 6), but sightings per 1000 km varied dramatically from region to region. The highest sighting rates were recorded between 40°S and 55°S in the southern Indian Ocean and south of Australia. Dramatically lower sighting rates were recorded in the South Atlantic, central Indian Ocean, Tasman Sea and southern Pacific Ocean. In the Antarctic, blue whales were generally recorded only in a few of the most southern 2° × 2° squares.

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Figure 6. Japanese Scouting Vessels (JSV) effort in km (top panel), and sightings per unit effort (bottom panel) in each 2° × 2° sector in the Southern Hemisphere. The JSV database covers the period from 1965 to 1987 but does not include effort and sightings for the northern Indian Ocean.

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Sightings from the SWFSC surveys in the eastern tropical Pacific were grouped into those off Mexico, those on or near the Costa Rica Dome and those near to or south of the equator (Fig. 7). Only sightings from the last grouping were analysed further in this paper.

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Figure 7. Southwest Fisheries Science Center surveys between 1986 and 2006 in the eastern tropical Pacific. Grey lines indicate primary search effort, while circles show both on-effort and off-effort sightings of blue whales. Only sightings and effort south of 5°N were included in the analyses presented in this paper.

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Strandings

We found records of 103 strandings in the study area (Appendix 3). Most of the strandings were reported from the south-east Pacific, in the northern Indian Ocean (Pakistan, India, Sri Lanka, Bangladesh, the Maldives), on the south and south-west coasts of Australia, and in north-west New Zealand (Fig. 4). Isolated strandings were also reported from Uruguay, New Caledonia, northern Australia and Indonesia, but none were reported from any African country. All strandings were of solitary individuals, although a notable stranding on 23 January 1946 in Trincomalee Harbour, Sri Lanka, was of a pregnant female that gave birth in the harbour the following day and was then towed to safety (Deraniyagala, 1948). Reported lengths ranged from 6.35 m to 29.3 m but most blue whales measured in recent times (after 1927) were shorter than the maximum pygmy blue whale length of 24.1 m (Ichihara, 1966), except for a 27.4 m whale reported at Orewa, New Zealand in 1978 (A. N. Baker unpublished data). In addition, bones from a 24.0 m blue whale stranded near Busselton, Western Australia & in 1898 reveal that it was a physically immature Antarctic blue whale (Bannister, Burton & Hedley, 2005), and the skeleton still exists of a properly measured 26.5 m blue whale stranded on 8 February 1908 north of Okarito, New Zealand (Waite, 1912; Stollman et al., 2005).

Mark-recaptures

There were 104 Discovery marks recovered from 95 individual whales (Appendix 4) and an additional 2191 Discovery marks that were not recovered (Fig. 8). Some blue whales were caught far from the mark position, but there was no obvious increase in the distance between marks and recoveries with increased time except that recoveries in the same season were usually closer to the mark position than recoveries after one season or more (Figs 8 and 9).

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Figure 8. Discovery mark placement (triangles, top panel) and recoveries of Discovery marks (arrows, other panels) of blue whales. The top panel shows the positions of all marks (grey ≤1973, black >1973), panels below zoom into a narrower latitudinal range to show all mark-recaptures. Mark-recapture pairs are split between those recovered in the same season, the following season, two seasons later and more than two seasons after the mark. The shortest mark-recapture path sometimes crosses the international dateline. Only the same-season recovery at 43°55′S 50°02′E was identified as a pygmy blue whale.

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Figure 9. Longitudinal movement between marks and recoveries of blue whales in the same season, after 1 year, 2 years and more than 2 years. Positive numbers indicate eastward movement and negative numbers westward movement.

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Most marked blue whales (n = 54) were caught in the same season, but 15 were caught more than two seasons later and one evaded capture for 13 years 10 months and 12 days. With one exception, mark-recapture pairs were all south of 53°55′S and between October and March and can be presumed to be Antarctic blue whales. The single exception was a blue whale marked at 56°15′S 49°03′E on 1 December 1962 that was identified as a pygmy blue whale when caught at 43°55′S 50°02′E on 4 April 1963 (Ichihara, 1966).

Acoustics

Acoustic recordings were distributed widely around the Antarctic, around the Indian Ocean, off northern New Zealand and in the south-east Pacific (Fig. 4). The earliest Southern Hemisphere acoustic recordings in the presence of blue whales were off Chile in 1970 (Cummings & Thompson, 1971). They described long (10–30 seconds), low-frequency (10–40 Hz), multi-unit sounds; all subsequent recordings of blue whales share these characteristics, but are also geographically distinct both within and between ocean basins. Distinct call types have been described in the literature associated with the following regions: the Antarctic, south-east Pacific, Madagascar, Australia, Sri Lanka and off northern New Zealand (e.g. Stafford, Nieukirk & Fox, 1999; McCauley et al., 2001; Stafford et al., 2004; McDonald, 2006; reviewed by McDonald, Hildebrand & Mesnick, 2006).

In all Antarctic regions, a unique call type sometimes referred to as the ‘28-Hz pulse’ or ‘28-Hz tone’ has been recorded together with the low-frequency downsweeps common to blue whales worldwide (Fig. 4) (Ljungblad, Clark & Shimada, 1998; Stafford et al., 1999; Clark & Fowler, 2001; Širovićet al., 2004; Stafford et al., 2004; McKay et al., 2005; Rankin et al., 2005; Ensor et al., 2006). This 28-Hz tone is now considered diagnostic of the Antarctic subspecies (Rankin et al., 2005) and has been recorded from sonobuoys on SOWER cruises (December–February) coincident with blue whale sightings or at night when blue whales had been seen during the day (Ljungblad et al., 1998; Clark & Fowler, 2001; Rankin et al., 2005; Ensor et al., 2006). Short recordings of Antarctic-type calls were also recorded 4–6 April 2004 near South Georgia (C. W. Clark & A. R. Martin, personal communication) which represents the furthest north they have been recorded in the Atlantic Ocean.

The seasonal occurrence of Antarctic blue whale calls can be obtained from moored instruments. Distinctive 28-Hz tones were recorded on instruments moored to the west and north of the Antarctic Peninsula in all months with strong seasonal peaks in February–May and October–November, and low numbers of calls during June–August during high ice concentration cover (Širovićet al., 2004). These 28-Hz tones were also recorded year-round from an instrument moored at 66°44′S 69°48′E with peaks in April–June, October–November and a dearth of calls in December–March, although this analysis is preliminary (McKay et al., 2005). Additionally, there are limited records of 28-Hz tones in mid and low latitudes during May to September in the Pacific and Indian Oceans, suggesting that at least some Antarctic blue whales migrate northwards in the austral winter (McCauley et al., 2004; Stafford et al., 2004; McDonald, 2006). In the eastern tropical Pacific, these calls were recorded in low numbers from May to September, with peak number of calls in July at 8°S 95°W and 8°S 110°W (Stafford et al., 1999). Near northern New Zealand (36°22′S 175°54′E), 28-Hz tones were recorded in May to July (McDonald, 2006). Off south-western Australia (∼34°54′S 114°06′W) they were recorded from May to November (peak in July) (McCauley et al., 2004; Stafford et al., 2005), and near Diego Garcia (∼7°S 72°E) from May–August 2002 (peak in July) (Stafford et al., 2004). Finally, 28-Hz tones were recorded near Crozet Island at 46°10′S 51°48′E but no seasonal information was provided (Samaran et al., 2006).

None of the other five blue whale call types have been recorded in the Antarctic south of 60°S. These other call types have usually been labelled as ‘pygmy’ blue whales and differ according to ocean basin. Three distinct call types have been recorded from the Indian Ocean (Alling et al., 1991; Ljungblad et al., 1998; McCauley et al., 2001), one from the south-east Pacific (Cummings & Thompson, 1971; Stafford et al., 1999), and one likely pygmy blue whale call type from the south-west Pacific (Kibblewhite, Denham & Barnes, 1967; McDonald, 2006), but no pygmy-type call has yet been recorded from the Atlantic Ocean.

The first of the three distinct Indian Ocean call types was recorded in the presence of blue whales off north-east Sri Lanka in February–April 1984 (Alling et al., 1991), and has since been recorded on bottom-mounted instruments near Diego Garcia in all months except February–April and July (Stafford et al., 2005). The second call type was recorded in late December 1996 on the Madagascar Plateau in the presence of nominal pygmy blue whales (Ljungblad et al., 1998). It has also been recorded at Diego Garcia in May–July (Stafford et al., 2005) and off Crozet Island (Samaran et al., 2006). The third call type, first described by McCauley et al. (2001) from moored hydrophones, has been recorded in south-western Australian waters during November–June (McCauley et al., 2004; Stafford et al., 2005), along the West Australian coast off Exmouth (21°S) in June–July and November–December (R. D. McCauley, unpublished data) and along southern Australia from Bass Strait westwards to south-western Australia (R. D. McCauley, unpublished data).

The south-east Pacific blue whale call type was first recorded on 30–31 May 1970 at 43°36′S 74°40′W off Chile (Cummings & Thompson, 1971), and has been recorded year-round on a hydrophone array in the eastern tropical Pacific, primarily at 8°S 95°W, with peak calling from March–September (Stafford et al., 1999). These calls were also recorded off Peru at 6°54′S 80°50′W in November 2000 (T. Norris, unpublished data). In addition to this ‘normal’ call type, a different call type was recorded during biopsy approaches off Chile during the 1997–98 IWC survey, apparently in reaction to the rapid approach of the survey vessel (Ljungblad & Clark, 1998).

The northern New Zealand call type consists of a single instance of these calls in the 1960s (Kibblewhite et al., 1967) together with four records in 1997 (McDonald, 2006).

Combined distribution from all sources

Where blue whales were present, this was often confirmed by multiple sources (Fig. 10). For example, although there were only rare detections of blue whales off northern New Zealand, these records included catches, sightings, strandings and acoustic detections.

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Figure 10. Distribution of blue whales in all months based on catches (×), sightings (○), strandings (▵), acoustic records (□) and Discovery mark positions (▿). Grey is used for positions ≤1973 and black for >1973.

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Monthly distribution

Most positional data were recorded during the austral summer season between October and April (Fig. 11). During summer, records were nearly circumpolar especially between November and March. The Antarctic region between 160°W and 70°W was hardly exploited before World War II, and was proclaimed a sanctuary from 1938/39 to 1954/55, after which catches were legal between January and March only, explaining the near-absence of catches in this region outside those months. During summer, blue whales were commonly recorded in temperate latitudes off the west coast of South America, in the northern Indian Ocean, in the Subantarctic, around southern Australia and in north-west New Zealand, but were largely absent from African waters. In winter months (April–September), high catches were reported off south-west Africa (especially Saldanha Bay), and Durban (Fig. 12). In these months, sightings and strandings continued in other areas. It is also notable that catches were reported in every month of the year at South Georgia, although numbers (and catch effort) decreased greatly in the winter months.

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Figure 11. Monthly distribution of blue whales during October to March based on catches (×), sightings (○), strandings (▵), acoustic records (□) and Discovery mark positions (▿). Grey is used for positions ≤1973 and black for >1973. Acoustic locations are annotated with the call type using numbers: Antarctic (1), South-east Pacific (2), New Zealand (3), Sri Lanka (4), Australia (5) and Madagascar (6); these numbers are concatenated when two or more call types were recorded at a single location.

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Figure 12. Monthly distribution of blue whales during April to September based on catches (×), sightings (○), strandings (▵), acoustic records (□) and Discovery mark positions (▿). Grey is used for positions ≤1973 and black for >1973. Acoustic locations are annotated with the call type using numbers: Antarctic (1), South-east Pacific (2), New Zealand (3), Sri Lanka (4), Australia (5) and Madagascar (6); these numbers are concatenated when two or more call types were recorded at a single location.

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DISCUSSION

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGEMENTS
  8. REFERENCES
  9. Appendices

The dataset assembled here allows for an updated examination of blue whale distribution and its association with environmental factors, migration patterns and the relative status of different populations of blue whales in the study area.

Distribution

Blue whales feed on euphausiids and other crustacean meso-zooplankton (e.g. Mackintosh & Wheeler, 1929; Yochem & Leatherwood, 1985). To maintain their great energetic demands, they search out the densest patches of their prey (Croll et al., 2005). It has previously been accepted that blue whales in the study area (particularly Antarctic blue whales) feed in the austral summer but fast during the winter breeding season (e.g. Mackintosh & Wheeler, 1929; Mackintosh, 1966). However, as detailed below, we found that their distribution year-round is linked to areas with known or inferred high densities of euphausiids, suggesting that their winter distribution also may be influenced by feeding opportunities (cf. Reilly & Thayer, 1990; Croll et al., 2005).

Blue whale distribution in the study area is strongly linked to latitude. Close to the Antarctic, blue whales were recorded along bands stretching across entire ocean basins, but at lower latitudes they are progressively more clustered, localized and compressed along the continental margins (Fig. 10). This pattern probably reflects euphausiid biogeography, with large Antarctic krill Euphausia superba at the highest latitudes, mid-sized Euphausia species in the mid latitudes and smaller Nyctiphanes species in coastal upwelling systems in the mid and low latitudes (see maps in Brinton et al., 2000). However, until better region-wide data become available, we must rely on environmental proxies for euphausiid aggregation such as bathymetry, frontal processes and phytoplankton biomass (Atkinson et al., 2004; Siegel, 2005).

Patterns of blue whale distribution in relation to environmental features are best summarized in Figs 1 and 10. At the largest scale, blue whales generally occurred in regions with high phytoplankton densities such as the productive Antarctic and Subantarctic waters, and in the upwelling systems of the Arabian Sea and the west coasts of South America and Africa. A major exception to this pattern is in the 35–45°S band between South America and Africa, and extending into the Agulhas Retroflection south of Africa, where few blue whales were reported despite high chlorophyll-a concentrations. Conversely, annual mean chlorophyll-a levels were intermediate to low south of Madagascar and around Australia, where blue whale sightings were numerous. These areas, however, undergo seasonal blooming (Fig. 2), and are thus under-represented in the annual mean. Blue whales were virtually absent year-round from the mid-latitude central gyres with lowest chlorophyll-a concentrations.

Blue whales were generally associated with waters deeper than the continental shelves. Shallow-water records were typically from regions with narrow continental shelves, but blue whales were virtually absent from the wide continental shelves off south-east Argentina, northern Australia and south-east New Zealand. In the Antarctic, they were most common on deep continental slopes (Kasamatsu, Matsuoka & Hakamada, 2000). Frequent sightings and strandings have been reported from Trincomalee Harbour, Sri Lanka, in waters shallower than 200 m, but deeper water (>500 m) is found near to this harbour (Alling et al., 1991). Blue whales also move through waters less than 50 m depth in Geographe Bay, Australia (C. Burton, unpublished data), around Chiloé Island, Chile (Hucke-Gaete et al., 2003), and in the Bonney Upwelling of south-east Australia, where the mean depth of 920 sightings was 93 m (P. Gill & M. Morrice, unpublished data).

Blue whale occurrence matched large-scale fronts closely in some regions, but not in others. Frontal regions define water masses with distinct physical properties and production regimes, which influence euphausiid biogeography (e.g. Longhurst, 1998). In addition, enhanced frontal dynamics, such as interaction with bathymetric features, cross-frontal exchange, splitting and merging, meandering, and eddy shedding, often result in front-associated phytoplankton blooms (Moore & Abbott, 2000, 2002). Antarctic catches were bounded to the north by the Antarctic Polar Front, and pygmy blue whale distribution in the Subantarctic was fairly well bounded by the Subantarctic Front and the North and South Subtropical Fronts (Fig. 1). Off the west coasts of South America and Africa, distribution extended from upwelling regions to the Equatorial Front. Blue whales south of Madagascar may be supported by biological enrichment from the interaction of the North Subtropical Front with the steep bathymetry of the Madagascar Plateau; interactions of this front with the Broken Plateau may similarly support aggregations west of Australia. However, there were no links with any fronts for concentrations of blue whales in the northern Indian Ocean, coastal Australia and around New Zealand.

The above discussion examined large-scale patterns of blue whale distribution in the study area. There are also regional particularities that deserve additional consideration. We therefore focus in more depth on 10 regions of special interest.

Antarctic

It can safely be assumed from a variety of sources that nearly all blue whales in the Antarctic are from the Antarctic (true) subspecies. First, based on the lengths of sexually mature females, nearly all (99.2%) catches taken south of 52°S were Antarctic blue whales (Branch et al., 2007). Second, genetic evidence shows a significant separation between samples taken south of 60°S (Antarctic blue whales) and samples from the Indian Ocean (pygmy blue whales) (Conway, 2005; LeDuc et al., in press). Third, acoustic data south of 60°S from SOWER cruises (austral summer) and moored instruments (year-round) have consistently recorded the distinctive Antarctic-type 28-Hz tones (Ljungblad et al., 1998; Clark & Fowler, 2001; Širovićet al., 2004; Stafford et al., 2004; McKay et al., 2005; Rankin et al., 2005; Ensor et al., 2006). To date, none of the other blue whale call types have been recorded south of 60°S.

Antarctic blue whales have a continuous circumpolar distribution, although catches were lower between 70°W and 160°W. Prior to 1938/39, little whaling was conducted in 70–160°W, presumably because there were few blue whales there. From 1938/39 to 1954/55, this region was proclaimed a sanctuary; thus, the majority of whaling in this region was conducted after 1954/55. The continuous circumpolar distribution of Antarctic blue whales is reinforced by recoveries of Discovery marks showing that they sometimes disperse over time widely around the Antarctic, as noted by previous authors (Brown, 1954, 1962). While they may show some fidelity to particular IWC Management Areas (the IWC divides the Antarctic into six roughly equal Areas for management purposes), they also cross the borders between Management Areas and have been caught on several occasions more than 100 degrees of longitude from their marking position. Circumpolar-wide acoustic records of 28-Hz tones further support their continuous distribution (Ljungblad et al., 1998; Clark & Fowler, 2001; Širovićet al., 2004; Stafford et al., 2004; McKay et al., 2005; Rankin et al., 2005; Ensor et al., 2006).

Nearly all blue whale catches in the Antarctic were between October and April (Figs 2 and 12). While Tynan (1998) found that highest krill densities and highest whale catches are aligned with the Southern Boundary of the Antarctic Circumpolar Current (not shown here), we found that the Antarctic Polar Front was a more useful indicator of the northern boundary of the Antarctic catches. Where the Antarctic Polar Front was farther south (70–130°W), the catches were more southerly, and where it was further north (50°W−60°E), catches were more northerly. Antarctic krill presence is not associated with any one oceanographic feature, but is determined by the presence of abundant phytoplankton near ice edges, continental shelves and dynamic frontal regions (Atkinson et al., 2004; Siegel, 2005).

It is striking that recent Antarctic sightings are in a much narrower ring close to the pack ice and the continental shelves (Figs 4 and 5), while most catches were further north. In part, this may be explained by greater sighting effort (from the IDCR/SOWER surveys) south of 60°S. Additionally, the Antarctic pack ice has retreated since the 1960s (de la Mare, 1997; Cotté & Guinet, 2007), although this conclusion is disputed by Ackley et al. (2003). As an alternative, their narrower present-day distribution may be explained by the ‘basin model’ of MacCall (1990): at higher densities, the Antarctic blue whales may have occupied a wider habitat range, but now that they are depleted to <1% of their original abundance (Branch et al., 2004), they are more concentrated close to the ice edge where krill is most abundant.

Central ocean basins

Blue whales are largely absent from the central portions of each of the major ocean basins in the study area, which are notable biological deserts, as evidenced by the very low chlorophyll-a concentrations in these regions (Fig. 1; McClain, Signorini & Christian, 2004).

In the central South Pacific, two Soviet cruises in 1973/74 and 1974/75 found no blue whales between 40°S and 60°S (Mikhalev, 1978), and the JSV database also recorded no sightings in the South Pacific (20–50°S 90–150°W) despite 42 335 km of search effort.

Few blue whales were recorded from the central South Atlantic. Large-scale studies based on ship reports reinforce this conclusion (Brown, 1958; Slijper, van Utrecht & Naaktegeboren, 1964): sightings of rorquals (not identified to species) were nearly absent in the central region while higher sighting rates were recorded close to the African coast and in the 30–40°S latitude strip. However, these high rorqual sighting rates in 30–40°S in the South Atlantic probably did not include any blue whales, given that in the JSV database only three blue whales were sighted in 35–50°S, 10°E−65°W during 352 554 km of effort (0.005 groups per 1000 km assuming mean group size of 1.56). Furthermore, few Soviet blue whale catches were taken in this band despite large catches of other cetacean species (Fig. 3; Yablokov et al., 1998).

In the south-central Indian Ocean, blue whale records were completely absent although numerous sightings and catches were recorded along the Australian coast, in the northern Indian Ocean and south of about 35°S. Rorqual sightings from large-scale ship studies matched the patterns observed in this paper: low sighting rates in the central Indian Ocean contrasted with high sighting rates on the oceanic periphery (Brown, 1957; Slijper et al., 1964). Soviet catch data show a similar pattern (Mikhalev, 2000), including zero blue whale catches in the central Indian Ocean despite some catches of other species there (Fig. 3; Yablokov et al., 1998).

South-west Atlantic (Brazil, Uruguay and Argentina)

The lowest sighting rate in the study area was from Costinha, Brazil where only three sightings were recorded during 46 273 hours of effort (da Rocha, 1983), to add to two Brazilian catches (one of which was originally recorded as being either a bowhead or a blue, and whose identity is thus questionable) and one stranding (Dalla Rosa & Secchi, 1997). A thorough review concluded that blue whales are nearly absent from Brazil (Zerbini et al., 1997). Isolated strandings were reported from Uruguay (Praderi, 1985) and Argentina (Burmeister, 1871, 1872), and in October 1993 the jawbones from a long-forgotten blue whale stranding were discovered in central Patagonia (Reyes, 2006). Most likely these few blue whales off eastern South America are Antarctic blue whales, although the Brazilian stranding could not be assigned unambiguously to either the Antarctic or pygmy subspecies (Dalla Rosa & Secchi, 1997). It is a mystery why there are so few blue whale records from this region despite intensive whaling and sighting effort (Figs 3 and 6; da Rocha, 1983), especially given its extensive use by other large cetaceans (Zerbini et al., 1997; Croxall & Wood, 2002; Reyes, 2006) and areas of high chlorophyll-a concentrations (Fig. 1b; Romero et al., 2006). However, it is worth noting that the high chlorophyll-a concentrations are over the broad continental shelf (Fig. 1a), which is probably shallower than the depths preferred by blue whales.

South-western Africa

Large catches were recorded from Saldanha Bay (South Africa) (n = 7969), Namibia (n = 1665), Angola (n = 1917) and Congo (n = 1). Saldanha Bay in particular was known to be a place frequented by a high percentage of immature blue whales in addition to some very large females (Mackintosh & Wheeler, 1929; Mackintosh, 1942). These catches occurred throughout the highly productive upwelling system of the Benguela Current (Carr & Kearns, 2003). Despite large historical catches, only two sightings of blue whales have been recorded from the entire west coast of Africa since 1973, suggesting that these blue whales were nearly extirpated by whaling. Recently, no sightings were recorded in 3644 hours of survey effort between March 2004 and September 2005 off central and northern Angola in deep waters (C. Weir, personal communication). No strandings have ever been reported from this coast, perhaps because it is sparsely inhabited. These blue whales are most likely to be Antarctic blue whales because (i) Antarctic blue whales were severely depleted by whaling (Branch & Butterworth, 2001b; Branch et al., 2004); (ii) an estimated >90% of sexually mature females caught were Antarctic blue whales (Branch et al., 2007); and (iii) a detailed study found that they were morphologically similar to Antarctic blue whales caught at South Georgia (Mackintosh & Wheeler, 1929).

South-eastern Africa

Catches with positional data in this region were recorded only at Durban, South Africa, and consisted of a mixture of immature and adult blue whales. In total, 2986 blue whales were caught off Durban. Additional catches (positions not available) were taken in south-east South Africa (n = 417) and Mozambique (n = 14) during 1911–16. Evidence from a variety of sources suggests that most catches here were originally Antarctic blue whales but by the end of the whaling period most catches and sightings were probably pygmy blue whales (Branch et al., 2007). This is not surprising given the close proximity to known pygmy blue whale grounds south of Madagascar (Best et al., 2003), and a pygmy blue whale reported caught at Durban (Gambell, 1964). Sightings during 1968–75 were rare and concentrated in March–May, while earlier catches peaked in May–July (Bannister & Gambell, 1965).

Madagascar and Subantarctic (southern Indian Ocean)

This region of numerous sightings and catches is known to be primary pygmy blue whale habitat in the summer. One of the highest sighting rates recorded was on the Madagascar Plateau: 36 groups per 1000 km (Best et al., 2003), while 1607 whales were recorded in the JSV database in the Subantarctic (2.9 groups per 1000 km in 35–50°S 30–100°E). These sighting rates are 500 times greater than in the South Atlantic and South Pacific and an order of magnitude greater than in the Antarctic. Calls recorded here in the presence of pygmy blue whales are distinctive (Ljungblad et al., 1998) and have also been recorded north-east of Madagascar near Diego Garcia (Stafford et al., 2005) and in the Subantarctic near Crozet Island (Samaran et al., 2006). South of Madagascar, localized wind-driven upwelling occurs in winter (Ho, Zheng & Kuo, 2004), and the East Madagascar Current regularly sheds energetic eddies that feed into the Agulhas Current off south-eastern Africa (Quartly et al., 2006). Sightings and catches extended over a broad area from Africa to Australia, and were just south of a band of high eddy variability extending from Madagascar to Australia (Palastanga et al., 2007).

Australia and Indonesia

Sighting rates off southern and western Australia were among the highest recorded (7.4–18.6 groups per 1000 km). These areas were also where Soviet whalers took large catches of pygmy blue whales, and where relatively many strandings have been recorded. Given the near continuous distribution of records from Tasmania to Indonesia, it is likely that these blue whales form one population. Recordings of blue whales off western Australia include Australia-specific calls, presumably from pygmy blue whales, which peak from February to May, and limited numbers of Antarctic-type calls from May to October (Ljungblad et al., 1997; McCauley et al., 2004; Stafford et al., 2004). Additionally, the 1898 stranding off south-west Australia was of a physically immature Antarctic blue whale, 24.0 m in length (Bannister et al., 2005). Thus, while the great majority of blue whales in this region are probably pygmy blue whales, a few Antarctic blue whales migrate here in the austral winter. Environmental factors driving biological enrichment and enhanced blue whale foraging in this region include upwelling, eddy shedding and current meandering. Upwelling is most evident along the southern coasts of Java and Sumbawa Islands, Indonesia (Hendiarti, Siegel & Ohde, 2004), in the eastern Great Australian Bight (McClatchie, Middleton & Ward, 2006) including the Bonney Upwelling region (Gill, 2002), and at Perth Canyon, Western Australia, where a strong subsurface chlorophyll maximum (i.e. not evident in satellite imagery) supports seasonal blue whale foraging (Rennie, McCauley & Pattiaratchi, 2006). Eddy shedding is evident in the Leeuwin Current (Fang & Morrow, 2003), and current meandering interacts with upwelling around Halmahere Island, Indonesia (Christian et al., 2004).

Northern Indian Ocean

Numerous catches were recorded off Oman and Somalia, and around the Maldives and Sri Lanka. Sightings and strandings were recorded year-round in high productivity portions of the northern Indian Ocean, especially off Somalia (Small & Small, 1991), the Maldives (Anderson, 2005) and Sri Lanka (Alling et al., 1991). Strandings were also reported from a much wider area (Bangladesh, Burma, India and Pakistan) than sightings and catches. Sighting rates were generally higher than in the Antarctic, except off Oman where sightings were rare. Calls recorded from Sri Lanka (Alling et al., 1991) are distinct from those recorded off Madagascar, Australia and around the Antarctic but have also been recorded south of the equator at Diego Garcia (Stafford et al., 2005). This region encompasses the Arabian Sea, a productive upwelling region during the south-west monsoon (Longhurst, 1998). Localized upwelling also occurs between the southern tip of India and Sri Lanka (Rao et al., 2006), where blue whales are known to feed.

It has been suggested that northern Indian Ocean blue whales are a separate subspecies, B. m. indica (Blyth, 1859). While this name is accepted as valid, and has nomenclatural priority over both brevicauda (Ichihara, 1966) and intermedia (Burmeister, 1871), the distinguishing features (if any) of northern Indian Ocean blue whales are poorly known (Rice, 1998). It seems more likely that northern Indian Ocean and pygmy blue whales belong to the same subspecies, based on Soviet catches, where the mean length of sexually mature females from the northern Indian Ocean is 69 ft (21.0 m), nearly identical to that for pygmy blue whales from the southern Indian Ocean, and in contrast to the ∼84 ft (25.6 m) from Antarctic catches (Branch et al., 2007). On the other hand, their geographical distribution is fairly discrete (Fig. 10), and their breeding cycle is 6 months out of phase with those in the southern Indian Ocean (Mikhalev, 2000, p. 151). It is noteworthy that a resident population of humpback whales in the northern Indian Ocean (particularly the Arabian Sea) also has a reproductive cycle shifted by 6 months compared with the Southern Hemisphere (Mikhalev, 1997b).

South-east Pacific (Chile, Peru, Ecuador)

Sightings, strandings and catches were recorded throughout the waters of Chile, Peru, Ecuador and the Galapagos in a nearly continuous distribution bounded to the south by the South Subtropical Front and to the north by the Equatorial Front. This population is supported by the rich upwellings along the extent of the Humboldt Current (Carr & Kearns, 2003), and by topographic and equatorial upwelling processes near the Galapagos (Palacios, 2004). Recent sighting rates from an offshore survey (Findlay et al., 1998) and from the inshore Chiloé Island-Corcovado region (e.g. Hucke-Gaete et al., 2003; Galletti Vernazzani et al., 2006) are one to two orders of magnitude higher than those recorded in the Antarctic (from the IDCR/SOWER, JARPA and JSV surveys).

Several lines of evidence confirm that blue whales in Chilean waters are not from the same population as those in the Antarctic. First, hundreds of blue whales were caught annually in Chile in the 1960s (Clarke et al., 1978) at a time when Antarctic blue whales numbered less than a thousand (Branch et al., 2004). Second, a feeding and nursing aggregation of blue whales was discovered in southern Chilean waters during the summer when Antarctic blue whales should be in polar waters (Hucke-Gaete et al., 2003). Finally, there was a distinct gap between the southernmost sightings at 44°S and the northernmost Antarctic records at 64°S, corresponding to the region between the South Subtropical Front and the Antarctic Polar Front (Fig. 10).

Acoustic data include a call type unique to the south-east Pacific (Cummings & Thompson, 1971; Stafford et al., 1999; T. Norris, unpublished data). In the eastern tropical Pacific, this call type was paired with the Antarctic call type during June–September although the Antarctic calls were recorded much more rarely (Stafford et al., 1999; Stafford et al., 2004).

The subspecific status of south-east Pacific blue whales remains a topic open for debate. The gap of 20° latitude between their southernmost distribution and the northernmost Antarctic records, and their high density peaking in summer months in Chile are evidence that they are not Antarctic blue whales. Aguayo (1974) asserts that 10 out of 168 examined Chilean catches were pygmy blue whales (but provides no details), and an examination of a stranded individual (Van Waerebeek et al., 1997) suggested more affinity to Antarctic blue whales than to pygmy blue whales. South-east Pacific blue whales have a unique acoustic call type (Cummings & Thompson, 1971; Stafford et al., 1999; T. Norris, unpublished data). Genetic evidence has suggested similar levels of divergences between Antarctic samples, Indian Ocean samples and those from the south-east Pacific (LeDuc et al., 2007). The mean length of sexually mature blue whales from Chile (23.5 m) is intermediate between pygmy (21.0 m) and Antarctic (25.6 m) blue whales (Branch et al., 2007). These lines of evidence led Branch et al. (2007) to hypothesize that these blue whales may belong to a separate as-yet undescribed subspecies, although this remains to be demonstrated.

New Zealand and south-west Pacific islands

A distinct grouping of catches, sightings and strandings was recorded from New Zealand, separated by the 155°E longitude line from blue whales recorded around Tasmania. In the JSV database, no sightings were recorded in the Tasman Sea despite high search effort. It seems reasonable to conclude that these blue whales are linked to those recorded directly north of New Zealand. This area is influenced by frontal dynamics at the Subtropical Front to the south and the Tasman Front to the north, and by upwelling at several sites along the coast of New Zealand (Longhurst, 1998). Sounds produced off northern New Zealand differ from those produced by pygmy blue whales from the Indian Ocean (McDonald, 2006; McDonald et al., 2006); however, these sounds were only recorded four times during a full year of monitoring and just once from acoustic data monitored in the early 1960s (Kibblewhite et al., 1967; McDonald, 2006). Two carefully measured New Zealand strandings are too long to have been pygmy blue whales: a 26.5 m individual in February 1908 (Waite, 1912), and a 27.4 m blue whale in April 1978 (A. N. Baker, unpublished data). Matters are complicated further in that reported Soviet catches in this area do not include length data but were considered to be pygmy blue whales (Mikhalev, 2000) and because Antarctic calls have been recorded from this area in the winter months (McDonald, 2006). The available evidence suggests that blue whales recorded here in austral summer months are probably a separate population of pygmy blue whales but further work on morphology, acoustics and genetics is needed to clarify their relationship to the described subspecies.

Migration

Antarctic blue whales

The classic theory for Antarctic blue whales holds that they migrate to the Antarctic in the austral summer to feed, and then migrate to a variety of more northerly locations in the winter to calve and mate (Mackintosh, 1966). Good supporting evidence is available for the winter migration of Antarctic blue whales to the west coast of South Africa, Namibia and Angola (e.g. Best, 1998). First, large females were recorded in south-west African locales with similar morphology to blue whales at South Georgia (Mackintosh & Wheeler, 1929). Second, Antarctic catches peaked in the austral summer, and south-west African catches peaked in the austral winter. Third, south-west African catches plummeted to near zero with identical timing to the substantial depletion in the Antarctic. Fourth, only two sightings have been recorded in the region since whaling ceased (although effort is limited), implying that blue whales off south-west Africa remain substantially depleted.

Similar evidence links Durban with Antarctic blue whales: size distribution, seasonal distribution of catches and a plummeting catch per unit effort (Best, 2003). However, later catches and sightings off Durban were primarily in March–May instead of the earlier catch peak in June–July; catch per unit effort decreased to 3% (Best, 2003) instead of the 0.3% levels expected (Branch et al., 2004); a pygmy blue whale was caught there in September 1963 (Gambell, 1964); and four out of 12 pregnant blue whales caught at Durban were shorter than 75 ft (IWC catch database). These data suggest that in later years most blue whales encountered at Durban were pygmy blue whales.

In areas other than southern Africa, the main evidence for migration comes from acoustic detections of the characteristic 28-Hz Antarctic call type and occasional strandings of Antarctic-length blue whales. Antarctic blue whale calls have been recorded in winter months in a variety of locations: the eastern tropical Pacific, the central Indian Ocean, south-west Australia and northern New Zealand (Stafford et al., 1999; McCauley et al., 2004; Stafford et al., 2004; Stafford et al., 2005; McDonald, 2006). These call detections are generally infrequent, suggesting small numbers of calling blue whales. Strandings might be expected to shed light on migration patterns but few unambiguous Antarctic blue whales have stranded and been examined: notably a 24.0 m physically immature blue whale in Australia in 1898 (Bannister et al., 2005), a 26.5 m female in New Zealand in February 1908 (Waite, 1912), and a 27.4 m individual in New Zealand in April 1978 (A. N. Baker, unpublished data).

While the acoustic detections provide evidence that Antarctic blue whales migrate to northerly locations in winter, it is still unknown what proportion migrate. Moored acoustic devices along the Western Antarctic Peninsula (Širovićet al., 2004) and in East Antarctica (67°S 70°E) (McKay et al., 2005) detected Antarctic blue whales year-round. Admittedly, these acoustic detections were greatly reduced in winter months, but it is likely that this reduction was partly due to the encroachment of heavy ice cover over the acoustic devices (Širovićet al., 2004), forcing the blue whales northwards. At South Georgia, although few vessels attempted whaling in the winter months, Risting (1928, p. 20) reported that 559 blue whales were taken during July–September in 1914–18, i.e. 5.0% of the 11 114 blue whales taken in those years (source: IWC). Hinton (1915, p. 155) also records that while humpbacks were present only between October and March around South Georgia, ‘finback and blue whale are to be found around the island at all times’. Thus, at least some Antarctic blue whales do not migrate northwards in winter. No information is available from Discovery marks since these were recovered only in the Antarctic (n = 103) and Subantarctic (n = 1) during summer months. Overall, the available evidence suggests that Antarctic blue whales generally do migrate to northerly locations in winter, although some overwinter in the Antarctic.

Pygmy blue whales

The migration patterns of pygmy blue whales are poorly known. High densities observed during summer months in the northern Indian Ocean, off southern Madagascar and Australia and around New Zealand provide evidence that these blue whales do not migrate to the Antarctic (Ichihara, 1966; Kato et al., 1995; Mikhalev, 2000; Gill, 2002; Best et al., 2003).

In the northern Indian Ocean, blue whales are present around Sri Lanka and India in all months of the year and seasonally around the Maldives (Alling et al., 1991; Anderson, 2005). The call type recorded off Sri Lanka from February to April was recorded from Diego Garcia from May to December (except July), suggesting some movement between these two areas on a seasonal basis. A more fine-scale analysis of seasonal movements within the northern Indian Ocean is ongoing and will be reported separately.

The pygmy blue whales recorded south of Madagascar appear to move southwards and spread longitudinally in the southern Indian Ocean in the summer. In January through March, pygmy blue whales are distributed almost continuously in the Subantarctic between Africa and Australia (Fig. 11). The call type recorded south of Madagascar in December was recorded in Diego Garcia (6°18′S 71°E) in May–July (Stafford et al., 2005), suggesting a northern migration in winter.

Around Australia and Indonesia, the monthly data suggest a migratory link between Australia and Indonesia around the western coast of Australia. As shown in Figs 11 and 12, blue whales have been recorded in Indonesian waters during May to November while high concentrations are reported from the southern coast of Australia mostly during the austral summer (November to May). Acoustic detections off West Australia (21°S) record blue whales apparently migrating northwards in June–July and southwards in November–December (R. D. McCauley, unpublished data). In July–October the acoustic detections from Cape Leeuwin, Australia (35°S 114°E) included Antarctic blue whales only, but from November to June Australian call types were often recorded there (McCauley et al., 2004; Stafford et al., 2004).

Off north-western New Zealand there is little evidence for migration, although it seems reasonable to hypothesize that some blue whales migrate from New Zealand northwards to the Pacific islands in winter. These blue whales were described as pygmy blue whales in Soviet catches (Mikhalev, 2000), although length data are not available for confirmation.

South-east Pacific blue whales

In the south-east Pacific, sightings and catches of blue whales peak in the summer months, while in August to November there are numerous records off Peru and the Galapagos. These data can be used to infer a migration from southern Chilean waters in summer to more northerly regions in winter, although the data also show that some blue whales remain in each of these regions all year.

Population status

Since the type and amount of effort differ substantially from region to region, the resulting sighting rates are only a qualitative measure of the status of the blue whale populations discussed here. For Antarctic blue whales, sightings remain rare in the Antarctic (0.17–0.52 per 1000 km) despite considerable effort during dedicated sightings surveys. Sightings are also concentrated at the edge of the pack ice, whereas historical catches were more broadly distributed, especially in the summer months. Recorded sightings are also rare (only two since the 1960s) off south-west Africa where large catches of Antarctic blue whales were taken in the 20th century (C. Allison, IWC catch database). This pattern is consistent with substantial depletion of Antarctic blue whales to a low point of 0.07–0.29% of pre-exploitation levels in 1973 (Branch et al., 2004). Until recently, there was little evidence for recovery in this subspecies, but Branch et al. (2004) showed statistical evidence that they are increasing at 7.3% per year (95% interval 1.4–11.6%), while remaining below 1% of their original levels.

Within the known distribution range of pygmy blue whales (Indian Ocean including Indonesian waters, south of Australia and north of New Zealand), there are areas with sighting rates one to two orders of magnitude higher than in the Antarctic. This is of particular interest because of the intensive effort associated with Antarctic sighting surveys compared with the lower effective effort in many pygmy blue whale areas. This may reflect a higher density and perhaps abundance of pygmy blue whales compared with Antarctic blue whales, although this may only apply to specific regions where survey effort has been directed. Given that catches of pygmy blue whales were much lower than Antarctic blue whales (∼13 000 vs. >330 000; Branch et al., 2004), and current densities in at least some places are higher, it is clear that pygmy blue whales are less depleted at present than Antarctic blue whales, although their status remains highly uncertain. Relatively high numbers of recent sightings and strandings of south-east Pacific blue whales, and a lack of decline in catches in the 1960s, suggest that this population is also less depleted than in the Antarctic, although, again, their status remains uncertain.

ACKNOWLEDGEMENTS

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGEMENTS
  8. REFERENCES
  9. Appendices

We are grateful for sightings and strandings contributed, and assistance received in many different ways, from the following sources: A. Alling, J. Barendse, L. Bedriñana, C. W. Clark, R. Constantine, J. Cotton, B. M. Dyer, P. Ensor, K. Evans, B. Haase, S. Heinrich, D. Hyrenbach, T. A. Jefferson, C. Kemper, F. Kennedy, S. Kromann, R. G. LeDuc, A. R. Martin, M. A. McDonald, S. A. Mizroch, M. J. Moore, S. Ohsumi, P. Olson, V. Peddemors, R. L. Pitman, R. Praderi, S. Reilly, D. Rice, H. Shigemune, A. Širović, E. Sullivan, P. Taylor, C. T. Tynan, R. Veit, I. Visser, C. Weir, A. N. Zerbini, members of the Oman Whale and Dolphin Research Group (R. Baldwin, T. Collins, L. Ponnampalam, F. Kennedy and G. Minton) and the New Zealand Department of Conservation. Frontal paths in the Southern Ocean were provided by I. M. Belkin, J. K. Moore and A. H. Orsi and the Costa Rica Dome by P. C. Fiedler. Chlorophyll-a data were obtained from the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE. Helpful comments on the manuscript were received from R. R. Reeves, P. J. Clapham and an anonymous reviewer. D.M.P. was supported by award No. N00014-05-1-0045 from the U.S. National Oceanographic Partnership Program. T.A.B. is very grateful for funding from the IWC and the South African National Antarctic Programme, without which this project would never have been attempted.

REFERENCES

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGEMENTS
  8. REFERENCES
  9. Appendices
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Appendices

  1. Top of page
  2. ABSTRACT
  3. INTRODUCTION
  4. METHODS
  5. RESULTS
  6. DISCUSSION
  7. ACKNOWLEDGEMENTS
  8. REFERENCES
  9. Appendices

APPENDIX 1

Coauthors:

  • T. A. Branch: Marine Research Assessment and Management Group, Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, South Africa.

  • K. M. Stafford: Applied Physics Lab, University of Washington, 1013 NE 40th, Seattle, WA 98105, USA.

  • D. M. Palacios: Joint Institute for Marine and Atmospheric Research, University of Hawaii, 1000 Pope Road, Marine Sciences Building, Room 312, Honolulu, HI 96822, USA; and Environmental Research Division, Southwest Fisheries Science Center, NOAA Fisheries, 1352 Lighthouse Avenue, Pacific Grove, CA 93950-2097, USA.

  • C. Allison: International Whaling Commission, The Red House, 135 Station Road, Impington, Cambridge, CB4 9NP, UK.

  • J. L. Bannister: The Western Australian Museum, Locked Bag 49, Welshpool DC, WA 6986, Australia.

  • C. L. K. Burton: PO Box 1076, Dunsborough, WA 6281, Australia.

  • E. Cabrera: Centro de Conservacion Cetacea (CCC), Casilla 19178, Correo Lo Castillo, Santiago, Chile.

  • C. A. Carlson: College of the Atlantic, Bar Harbor, Maine, USA.

  • B. Galletti Vernazzani: Centro de Conservacion Cetacea (CCC), Casilla 19178, Correo Lo Castillo, Santiago, Chile.

  • P. C. Gill: Blue Whale Study, Australocetus Research, C/- Post Office, Narrawong, Vic. 3285, Australia.

  • R. Hucke-Gaete: Instituto de Ecología y Evolución, Universidad Austral de Chile, Casilla 567, Valdivia, Chile.

  • K. C. S. Jenner: Centre for Whale Research (WA) Inc., PO Box 1622, Fremantle, WA 6959, Australia.

  • M.-N. M. Jenner: Centre for Whale Research (WA) Inc., PO Box 1622, Fremantle, WA 6959, Australia.

  • K. Matsuoka: The Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan.

  • Y. A. Mikhalev: South-Ukrainian Pedagogical University, Solnechnaya 10, no. 45, Odessa 65009, Ukraine.

  • T. Miyashita: Cetacean Resources Management Section, National Research Institute of Far Seas Fisheries, 5-7-1 Orido, Shimizu-ku, Shizuoka 424-8633, Japan.

  • M. G. Morrice: Whale Ecology Group, School of Life and Environmental Sciences, Deakin University, PO Box 423, Warrnambool, Vic. 3280, Australia.

  • S. Nishiwaki: The Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan.

  • V. J. Sturrock: 41 Wasley St, Mount Lawley, WA 6050, Australia.

  • D. Tormosov: Ulitsa Karla Marksa, D.76 KV5, Kaliningrad 236000, Russian Federation.

  • R. C. Anderson: P.O. Box 2074, Male', Republic of Maldives.

  • A. N. Baker: 8 Waters Lane, RD 2 Kerikeri, Bay of Islands, New Zealand.

  • P. B. Best: MRI Whale Unit, c/o South African Museum, PO Box 61, Cape Town, 8000, South Africa.

  • P. Borsa: I R D – Génétique des Populations, BP A5, 98848 Nouméa cedex, Nouvelle-Calédonie.

  • R. L. Brownell, Jr: Southwest Fisheries Science Center, NOAA Fisheries, 1352 Lighthouse Avenue, Pacific Grove, CA 93950-2097, USA.

  • S. Childerhouse: Marine Conservation Unit, Department of Conservation, Level 5, 53 Boulcott St, PO Box 10-420, Wellington, New Zealand.

  • K. P. Findlay: Oceanography Department, University of Cape Town, Private Bag, Rondebosch 7701, South Africa.

  • T. Gerrodette: Southwest Fisheries Science Center, NOAA, U.S. National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.

  • A. D. Ilangakoon: 215 Grandburg Place, Maharagama, Sri Lanka.

  • M. Joergensen: Broagergade 1, 3.th., 1672 Copenhagen V., Dk – Denmark.

  • B. Kahn: APEX Environmental, Suite 102, Jl. Bypass Ngurah Rai No. 379, Sanur – 80228, Bali, Indonesia.

  • D. K. Ljungblad: Ljungblad Associates, P.O. Box 6, Elk Mountain, WY 82324, USA.

  • B. Maughan: 9 Bovet St, Wellington, Somerset, TA21 8JJ, UK.

  • R. D. McCauley: CMST Curtin University, GPO Box U 1987, Perth 6845, Western Australia, Australia.

  • S. McKay: Whale Ecology Group, School of Life and Environmental Sciences, Deakin University, PO Box 423, Warrnambool, Vic. 3280, Australia.

  • T. F. Norris: Bio-Waves, Inc., 517 Cornish Dr, Encinitas, CA 92024, USA.

  • Oman Whale and Dolphin Research Group: P.O. Box 2531, CPO 111, Sultanate of Oman.

  • S. Rankin: Southwest Fisheries Science Center, NOAA, U.S. National Marine Fisheries Service, 8604 La Jolla Shores Drive, La Jolla, CA 92037, USA.

  • F. Samaran: Centre d'Etudes Biologiques de Chize, CNRS, Villiers-en-Bois, France.

  • D. Thiele: Whale Ecology Group, School of Life and Environmental Sciences, Deakin University, PO Box 423, Warrnambool, Vic. 3280, Australia.

  • K. Van Waerebeek: Peruvian Centre for Cetacean Research (CEPEC), Museo de Delfines, Pucusana, Peru.

  • R. M. Warneke: Blackwood Lodge, 1511 Mt Hicks Road, Wynyard 7325, Australia.

APPENDIX 2

List of sources used to obtain sightings data together with the number of associated records, the listed number of groups sighted and the number of whales sighted, alphabetized by source name. A ‘group’ could be either a school or feeding aggregation depending on the source. Listed sightings are those with associated positions, many papers noted additional sightings without positions. Latitudes and longitudes are given in whole degrees and rounded to encompass the study region. Where sources are ‘unpubl.’ this means ‘unpublished data’. For totals, each record contains ≥1 group and ≥1 whale. Mean group size is based on all records containing both the number of groups and number of whales. Total effort in days is based on the assumption that 10 hours of effort equals 1 day. For records from the eastern tropical Pacific only the sightings and effort south of 5°N were included.

SourceRegionDatesEffortRecordsGroupsWhalesAve group size
Aguayo (1974)Coastal Chile 43–46°SMar, Dec 1966Not recorded2293.67
Aguayo et al. (1998)SE Pacific 26–34°S 91–111°WSep 1994, Jun 1995770.5 hours3362.00
Alling et al. (1991)East coast, Sri LankaJan–Apr 1983–84890 hours (49 sightings)138138
Anderson (2005), R. C. Anderson unpubl.MaldivesNov–Apr 1999–2004161 days (11 sightings)1414151.07
Anonymous (1987a)Oman28 Oct 1985Opportunistic1122.00
A. N. Baker, unpubl.New Zealand 171–177°E 33–42°S1981, 1984, 1998–2004Opportunistic3131401.29
Ballance et al. (1996), Ballance & Pitman (1998)Indian OceanMar–Jul 199592 days; 403.9 hours; 9783.9 km1717271.59
Ballance et al. (2001)Maldives 3–8°N 72–74°EApr 199820 days; 155.5 hours; 1700 km4441.00
Best et al. (2003)Madagascar Plateau 25–35°S 40–45°EDec 199623 days; 2859.9 km1031031311.27
P. B. Best, unpubl.Saldanha Bay, South Africa1964–2003Opportunistic4441.00
P. B. Best, unpubl.Durban, South AfricaMar–Sep 1968–755545 boat days + 1592 385 aerial km6262711.15
Blokhin (1981)Southern Australia 29–45°S 113–148°E2–28 Mar 19795839 km77233.29
Borsa & Hoarau (2004)New Caledonia, 22°S 167°E29 Dec 2001–27 Jan 2002Opportunistic1111.00
P. Borsa, unpubl.Kerguelen Is., 48°S 71°EMar 1985Opportunistic1111.00
P. Borsa, unpubl.Indonesia, 2°N−11°S 122–137°E1995–2004270 hours2273.50
Bowles et al. (1994)Heard Island 53–54°S 74–75°E19 Jan−3 Feb 1991162.75 hours; 2412 km2221.00
C. L. K. Burton, unpubl.Geographe Bay, Australia 34°S 115°ESep–Dec 1994–2005750 days; ∼2600 hours (372 whales)1261262702.14
J. L. Bannister & C. L. K. Burton, unpubl.Western Australia 31–33°S 115°ENov–May 2000–0512 209.2 aerial km (227 sightings)2522522821.12
Cabrera, Carlson & Galletti Vernazzani (2005), Galletti Vernazzani et al. (2005, 2006)NW Chiloé Island, Chile 40–43°S 73–75°WFeb–Apr 2004–06108.3 hours; 1714.2 km (138 sightings)1841843211.74
Cawthorn (1983)New Zealand 38°S 141°EFeb 1982Opportunistic1111.00
Cawthorn (1988)New Zealand 40°S 139°EJul–Aug 1986Opportunistic13217.00
Chittleborough (1953)Western Australia 23°S 114°ESep–Oct 1952Not recorded1111.00
Clarke & Ruud (1954)Antarctic 53–62°S 47°W−15°ENov–Dec 195327 days1235
Clarke et al. (1978)Chile 28–37°SNov–Dec 19643876 km3341.33
Corbett (1994)S Indian Ocean, MauritiusJul 1991–Jul 199216 days8891.13
Cummings & Thompson (1971)Guafo Island, Chile 44°S 74°W30–31 May 1970Opportunistic14
da Rocha (1983)Costinha, Brazil1966–19812771 days; 46 273 hours; ∼943 000 km33
de Boer (2000)Antarctic, Indian OceanNov 1999–Jan 200022 920 km15102.00
Donovan (1984a,b)Peru 10°S−10°N 78–110°WNov–Dec 198216 437 km1212161.33
B. M. Dyer, pers. comm.Marion Island 47°S 38°EApr 2005Opportunistic3382.67
Eyre (1995)Sydney, Australia to Suez CanalMay–Jul 199345 days; 16 974 km4441.00
Eyre (2000)Mauritius to SingaporeApr 200015 days; 6130 km1111.00
Findlay et al. (1998)Chile 18–53°SDec 1997–Jan 1998389 hours 58 minutes; 8248.6 km4040481.20
Gambell, Best & Rice (1975)SW Indian Ocean 20–42°S 30–67°ENov 1973–Feb 197413 271 km77152.14
Gill (2002), P. C. Gill, unpubl.Victoria, Australia 37–40°S 139–144°EFeb 1998–May 200238 996 aerial km (290 sightings)3583585321.49
P. C. Gill & M. G. Morrice, unpubl.Victoria, Australia 35–40°S 134–144°EDec 2002–Feb 2006Unknown72972910131.39
Gordon, Papastavrou & Alling (1986)Trincomalee Bay, Sri Lanka 8°N 81°EMar 1984Opportunistic66
Gunaratna, Obeyesekera & Hahn (1985)SW Sri Lanka 5–7°N 79–81°EMay 19856 days1122.00
B. Haase, pers. comm.Galapagos Islands28 Feb 2003Opportunistic1111.00
Hucke-Gaete (2004), Hucke-Gaete et al. (2003, 2005, 2006), R. Hucke-Gaete, unpubl.Coastal Chile 29–53°SJan–Dec 1998, 2001–2006; but mostly Jan–Apr15.72 aerial hours (23 sightings); 625.36 boat hours (118 sightings)1581584292.72
D. Hyrenbach, pers. comm.S Indian Ocean 47°S 67°EFeb 2004Opportunistic2221.00
IDCR/SOWER, IWC unpubl.Surveys south of 60°S, plus transitsDec–Mar 1978–2005237 988.1 km (124 sightings)2422424902.01
A. D. Ilangakoon, unpubl.North-west Sri Lanka 6–9°N 79–82°E1987, 1994, 2003–0563 hours 49 minutes; 617.2 km (1 sighting)1515251.67
JARPA, Matsuoka et al. (2006), K. Matsuoka & S. Nishiwaki, unpubl.Antarctic and S Indian Ocean, 40°E−180°–140°W, mostly S of 60°SNov–Mar 1989–2005423 928 km (143 sightings)2532534321.71
K. C. S. Jenner, M.-N. M. Jenner & V. J. Sturrock, unpubl.Western Australia, 20–33°S 113–117°E1993, Feb 2000–Apr 20051612 hours; 24 572 km4554555481.20
M. Joergensen, unpubl.Chile 43–44°S, 49°SFeb 20041 day1010151.50
JSV, Miyashita et al. (1995), T. Miyashita, unpubl.Southern HemisphereDec 1965–Feb 19874 827 370 km (2520 whales)7992410
Kahn (2000, 2002)Komodo, IndonesiaSep–Oct 2000, Oct 2001227.25 hours; 4430.7 km3331.00
Kahn (2005)Solor-Alor, IndonesiaApr–May 200579.75 hours; 1162.9 km88
Kasuya & Wada (1991)Equatorial Indian OceanMar 19824295 km28
Kato et al. (1996)Southern Australia 31–45°S 113–149°EDec–Jan 1996∼44 days5252601.15
Leatherwood (1986)Antarctic, S. Indian1874, 1979Opportunistic14
Leatherwood et al. (1984)Northern Indian Ocean; Sri LankaApr 1983; 3 May 19834023 km (1 sighting); 4 hours (9 sightings)9991.00
A. R. Martin, pers. comm.West of South Georgia10 Feb 2006Opportunistic216
B. Maughan, unpubl.South Atlantic 0–70°SOct–Apr 1997–2001Opportunistic44
Moore et al. (1999)Falkland to S Georgia 51–55°S 34–58°WJan–Feb 19972266 km1122.00
Ohsumi & Shigemune (1993)Pacific 36°N−30°S 141°E−145°WAug–Oct 195713 479 km (in Southern Hemisphere)2323441.91
Oman Whale and Dolphin Research Group, unpubl.Oman 16–24°N 54–59°EOct–Apr 1996–200512 417 km (4 sightings)77111.57
Palacios (1999a,b), D. M. Palacios, unpubl.Galapagos 3°N−3°S 90–107°W1978–1995190 days; 31 390 km (8 sightings)1717362.11
Parker (1978)Melbourne, Australia to Mawson, AntarcticaDec 1976, Feb–Mar 197734 days; ∼136 hours12
V. Peddemors, pers. comm.Indian Ocean 37°S 10°E20 Oct 1987Opportunistic1122.00
R. L. Pitman, pers. comm.Peru; South GeorgiaMar 1982, Dec 1985; Jan 2003Opportunistic1717523.06
Puddicombe (1986)New South Wales, Australia 37°S 150°E16 Aug 1984Opportunistic1111.00
Ramirez (1985)Peru, 3–6°S 81–84°EOct–Dec 19833014.6 hours (852.2 searching)1079
Rudolph, Smeenk & Leatherwood (1997)Indonesian archipelagoJun–Sep 1990–93Opportunistic3362.00
Slijper (1962)Indian Ocean 11°N 60°E23 Sep 1953Opportunistic140
Small & Small (1991)Somalia 10–14°N 44–52°EAug 1985–May 19872615 hours; 32 062.9 km66
SWFSC cruises, T. Gerrodette, unpubl.Eastern tropical PacificAug–Nov 1986–1990, 1992, 1998–2000, 2003, 2006104 691.9 km (47 sightings)57571202.11
Thiele (2005)North-west Australia 13–16°S 123–130°ESep 2004125 hours1111.00
D. Thiele, unpubl.Australia to AntarcticJul 1995–Dec 2004∼1244 days2525542.16
Tynan (1996)Southern Indian Ocean 82–115°EDec 1994–Jan 199550 days2221.00
Valdivia et al. (1983)Peru 3–8°S 80–86°WFeb–Mar 19823400 km1414
Van Waerebeek et al. (1997)Chile 36–44°S 74–75°W1970, 1982, 1983, 1995Opportunistic4492.25
Wade & Friedrichsen (1979)Eastern tropical PacificJan–May 1971, 1975–76Unknown1111.00
Wheeler (1946)Central Atlantic 20°SAug–Sep 194315 days1111.00
Whitehead et al. (1983)Sri Lanka and MaldivesOct–Dec 198340 days1111.00
Wray & Martin (1983)Indian Ocean 45°S−7°N 42–96°EOct–May 1836–1888Opportunistic1515
Total   4383≥4389≥80581.56

APPENDIX 3

Blue whale strandings in the Southern Hemisphere and northern Indian Ocean, ordered by date of stranding. The source is the reference from which the information was obtained; if this was not the original reference, then the original reference is also listed. Where species identity was uncertain the stranding was generally excluded from this list, unless later authors confirmed that it was a blue whale. Most locations were obtained by reading the position from Google Earth, and were typically accurate to at most two decimal places; however, four decimal places are given to account for strandings with more detailed information and to avoid strandings being placed on land. Negative latitudes are south of the equator; negative longitudes are west of the Greenwich meridian.

SourceDateSexLength (m)LatitudeLongitudePosition nameNotes
  • *

    Details of original reference have not been obtained or were not listed in citing paper.

Guiler (1978) from Hobart Town Gazette6/5/1825 29.3−42.7833147.0667New Norfolk, Derwent River, Tasmania, Australia 
Blyth (1859)15/8/1842 27.421.000092.1833Chittagong coast about 21°N, BangladeshID uncertain, length ‘as alleged’
Blyth (1859)1851 25.618.783393.9667Juggu/Amherst Is., S of Ramri, E of Cheduba on Arakan coast, Burma (Myanmar)Skeleton in Indian Museum, Calcutta (Jones, 1953); according to Rice (1998) some authors erroneously recorded location as Sondip or Sordip
Blyth (1859)c.1858 27.48.883376.5667Quilon, IndiaID uncertain
Dixon & Frigo (1994) and M'Coy (1867)Aug 1866 27.4−38.3333144.3000Jan Juc, outside Port Phillip Heads, Victoria, AustraliaTotal length recorded, baleen black
Burmeister (1871, 1872)14/8/1866Female17.7−34.3000−58.4500Mouth of Río Luján, near Buenos Aires, ArgentinaType specimen for B. m. intermedia
Anonymous (1874)25/7/1874 26.5−41.0927146.0921West side of Leven Estuary (Ulverstone), Tasmania, AustraliaLength exclusive of tail, weight estimated 100–150 tons
Moses (1947)1874 14.412.833374.8333Mangalore, IndiaSkeleton in Madras Museum, ID confirmed in Gibson-Hill (1950)
Anderson (1878)∼Nov 1874  22.500091.4167Sandwip (formerly Sondip) Island, BangladeshYoung whale
De Silva (1987) from Murray (1884)1879  24.800067.0167Clifton beach, Pakistan 
R. M. Warneke, unpubl.27/7/1887 19.2−38.3333145.4167West of Warrnambool, Victoria, Australia 
De Silva (1987) from Haly (1894)Sep 1894 19.86.233380.0500Ambalangoda, Sri LankaSkeleton in Colombo Museum
Bannister et al. (2005)1898 24.0−33.6500115.3167Near Busselton, Western AustraliaPhysically immature Antarctic blue whale, skeleton in WA Museum
Pillay (1926) and James & Soundararajan (1979)1901 ∼228.100077.4000Rajakamangalam, 5 miles south of Muttum lighthouse between Colachel and Cape Comorin, IndiaTotal length estimated from jaw bone lengths of 5.56 m each, lower jawbone at Travancore Museum
Waite (1912)8/2/1908Female26.5−43.1333170.2333Near Commissioner's Point, 10.5 km north of Okarito, New ZealandLength from tip of snout to notch of tail, 30.2 m over curves of back; skeleton at the Canterbury Museum, Christchurch (Stollman et al., 2005)
Kinnear (1915)Jan 1911 21.316.966772.2833Viziadrug, Ratnagiri District, IndiaMeasured from nose to tip of tail in straight line, blue-black baleen
Prater (1915)11/12/1914Male12.516.800073.3167Dhabool, 155 km south of Bombay, IndiaMeasured from tip of snout to tip of flukes, ID uncertain
Reuter (1919)Dec 1916 27.28−7.7000107.7500Pameungpeuk, between Tjilauteureun and Tjikelet, Java, IndonesiaLength from extremities of flukes to tip of lower jaw, skeleton in zoology museum in Bogor
R. M. Warneke, unpubl.4/7/1923Male22.6−38.6667145.5833‘The wreck’, Wonthaggi, Victoria, Australia 
A. N. Baker, unpubl.1/1/1925Female30−36.5667174.7167Orewa, New Zealand 
Waite (1926)5/8/1925 7.42−34.2500138.2167Head of Gulf St Vincent, South Australia, AustraliaJuvenile, carefully measured
Moses (1947)Nov 1927 28.79.966776.2333Cherai, Cochin, IndiaSkeleton at St. Aloysius College, Mangalore, India
Rudolph et al. (1997) from Delsman (1932)Dec 1931 17−7.2167113.2333Sampang, Madura Island, Indonesia 
De Silva (1987) from Pearson (1932)*26/5/1932Male 8.533381.1500Tamblegam Bay, Trincomalee, Sri Lanka 
De Silva (1987) from Pearson (1932)*30/6/1932 20.18.466781.2167Koddiyar Bay, Trincomalee, Sri Lanka 
Deraniyagala (1960)6/2/1934 15.145.933380.5333Polhena, Matara (S.P), Sri LankaDescribed as fin whale but uniform black colour and all-black baleen; photo in De Silva (1987)
Jones (1953)Jan/Feb 1934  21.683388.1667Jambudwip, Bengal coast, IndiaDecomposition advanced
McCann (1934)7/5/1934 15.8 or ∼21.318.900072.8000Colaba Reclamation, Mumbai, IndiaExact location difficult to determine
Deraniyagala (1965)10/1/1939 ∼19.56.083380.1333Dodanduwa (S.P), Sri LankaLength estimate uncertain
Moses (1940)21/3/1939Female24.122.400068.9500Mulvel, Okhamandel, India 
Deraniyagala (1948)23/1/1946Female18.38.566781.2167Trincomalee Harbour, Sri LankaGave birth the next day in the harbour, towed to safety
Deraniyagala (1960)8/4/1949  6.883379.8500Bambalapitiya (W.P.) Colombo, Sri Lanka 
Chari (1951)14/5/1951 20.720.200072.7500Umargam, 160 km from Bombay, IndiaDecomposition advanced, 20.7 m from tip of snout to centre of flukes, some later sources erroneously reported as 22.6 m
Wakefield (1967)Apr 1955 18−38.4167144. 1833Anglesea, 50 miles SW of Melbourne, Victoria, AustraliaApproximate length
Wakefield (1967)c. 1957 18.3−38.2667141.8500Fitzroy River mouth, Portland Bay, Victoria, Australia 
Kewalramani (1969)27/12/1960Female23.821.533372.6833Soonvai Creek near village Ganeshghan in Bhal area of Vallabhipur Taluka, Bhavsagar Dt., Gujarat, IndiaLocation uncertain, some later sources erroneously reported as 23.4 m on 7/12/1960
Daniel (1963)23/2/1963 20.2823.066772.7167Village Gavier, near Magdalla Port, 11 km from Surat, Gujarat, India 
Al-Robaae (1974)6/6/1963  29.333348.1167In muddy area, ‘Kadguma’, Kuwait; location uncertainSkeleton at Natural History Museum, Shuaikh Secondary School, Kuwait
Nagabhushanam & Dhulkhed (1964)21/4/1964 15.7613.416774.6750Muloor village, IndiaDecomposition advanced, length from tip of lower jaw to fluke notch
Siddiqi (1968)1965  25.266763.4833Juddi near Pasni, Mekran coast, PakistanLocation of ‘Juddi’ not known, lower jaw 3.0 m, skeleton in Zoological Survey Museum, Karachi, Pakistan
De Silva (1987)3/4/1965  6.883379.8500Wellawatte (W.P.), Sri Lanka 
De Silva (1987)14/4/1965  9.000080.9500Kokkilai near Pulmoddai (E.P.), Sri Lanka 
James & Soundararajan (1979)5/2/1966 13.659.283379.1167Mandapam (Palk Bay), IndiaPutrefied specimen
Venkataraman & Girijavallabhan, 1966)25/5/1996 13.5111.250075.7667Kannanparambu, 1 km south of South Beach, Calicut, IndiaCalicut = Kozhikode, flipper:TL 1:8.6, baleen missing, ID uncertain
R. M. Warneke, unpubl.6/2/1967 18.3−41.1167146.1333Three Sisters Island, Tasmania, AustraliaApproximate length
Siddiqi (1968)Jun 1967 18.325.216763.40005 miles west of Pasni, Makran coast, PakistanLower jaw 5.5 m, in Zoological Survey Museum, Karachi, Pakistan
Bensam, Vincent & Mahadevan Pillai (1972)2/4/1969Female11.268.783378.1667Tuticorin, Gulf of Mannar, IndiaJuvenile, alive but shot and killed before brought to shore; ID uncertain
IWC catch database, Bannister et al. (2005)May 1973Female −35.0500117.8833Princess Royal Harbour, Albany, AustraliaProcessed, yielded 118 barrels
Al-Robaae (1974)Unknown  23.6167158.6000Entangled in submarine telegraph cable Muscat, OmanLocation named as Masket, Arabia, in original
Bannister et al. (2005)May 1974  −35.0667117.8667Princess Royal Harbour, Albany, WA, Australia 
Cawthorn (1978)1975  −39.1167173.9500Onetai Beach, Taranaki, New Zealand 
De Silva (1987)Mar 1976Female 6.933379.8500Galle Face, Colombo (W.P.), Sri LankaMother and calf
R. M. Warneke, unpubl. and Leatherwood (1986)5/4/1976Male17.5−38.3833142.0500Levy's Point, Victoria, Australia 
Marichamy, Rajapandian & Srinivasan (1984)20/12/1976Female6.358.266777.9000Near Ovari, Gulf of Mannar, IndiaImmature female
James & Soundararajan (1979)4/10/1977Female10–129.283379.1833Pamban, Palk Bay, IndiaEntangled live in gillnet
A. N. Baker, unpubl.30/4/1978 27.4−36.5667174.7167Orewa, New Zealand 
Leatherwood (1986) from Fernando (1981)*9/2/1981  7.583379.7833Chilaw, Sri Lanka 
Praderi (1985)9/7/1983 18.3−34.4333−57.6000Uruguay 
Venkataramanujam, Paulraj & Ramadhas (1984)11/9/1983 11.678.200077.1667Erayumanthurai near Thengapattinam, Tamil Nadu, IndiaBlack baleen plates, advanced decomposition
Anderson, Shaan & Waheed (1999)1984 197.016773.2500H.A. Dhidhoo, floating at sea, Maldives 
Van Waerebeek et al. (1997)24/2/1984 23−36.6167−72.9500Coliumo Bay, near Tome, Chile 
Anderson et al. (1999)30/1/1985 223.516773.5667V. Thinadhoo, floating off V. Maadhiggaru, MaldivesApproximate length
Anderson et al. (1999)16/2/1985 212.500073.3167Th. Vilufushi, floating near reef, rotten, MaldivesApproximate length
Somasekharan & Jayaprakash (1987)31/9/1985Male10.39.966776.2333Chappa Beach, Narakkal, Cochin, IndiaDate may be 31/8/1985; total length 7.7 times flipper length, identification uncertain.
A. D. Ilangakoon, unpubl.11/7/1986 18.97.580779.8047Chilaw (north-west coast) Sri Lanka 
Anonymous (1987b)18/10/1986 1310.900075.8833Tirur beach, IndiaPhotograph provided
Smith et al. (1997)19/1/1987 21.918.333394.3333One mile from shore, Andrew Bay (Thabyugyaing), Myanmar (Burma)Skeleton 17.4 m long, now in Yangon Zoological Gardens
Rudolph et al. (1997)22/6/1987 23.5−3.2667127.1167Namlea, Buru Island, IndonesiaSkeleton in Ambon Museum
Lal Mohan (1992)29/9/1988Female19.212.166776.5000Paravana, near Calicut, IndiaFlippers 2.5 m, 1/7 total length; 80 throat grooves
Nammalwar et al. (1989)10/12/1988Male15.1616.916782.3167Motupally, near Ramachandrapuram, Andhra Pradesh, Prakasam District, IndiaMeasured from tip of upper jaw to notch of caudal fluke
C. Kemper, South Australian Museum, pers. comm.19/9/1989Female −34.7300138.5000Gulf St. Vincent, Australia 
R. M. Warneke, unpubl.4/12/1991Male20−39.9500143.8500British Admiral Beach, King Island, Tasmania, AustraliaApproximate length
A. N. Baker, unpubl.1/3/1992Female16.4−35.8167174.5333Whangarei harbour, New Zealand 
Dalla Rosa & Secchi (1997)29/4/1992Female23.1−33.7500−53.38002 km from Chui Bar southern Brazil, near border with UruguayGenetic sample held by L. Pastene
Dixon & Frigo (1994)5/5/1992Male18.17−38.4833144.0167Cathedral Rock, 5 km NE of Lorne, Victoria, Australia 
Bannister et al. (2005)Mar 1993  −32.2000 115.6667Garden Island, WA, Australia 
James, Menon & Pillai (1993)2/5/1993 269.966776.2333Chellanam, Cochin, IndiaCarcasse putrefied, length approximate
LeDuc et al. (1997)14/6/1993  −34.5167135.3167Australia 
Van Waerebeek et al. (1997)30/8/1993 12.53.6048−77.2042Periquillo beach, Colombia 
Mohanraj, Somaraju & Seshagiri Rao (1995)9/5/1994Male11.7317.833383.4167Off Mangamaripeta, 12 km north of Visakhapatnam, IndiaLive male caught in drift gillnet, length from tip of upper jaw to notch of caudal fluke, some later sources erroneously list date as 9/5/1995
A. N. Baker, unpubl.11/9/1994Male20.6−36.5667175.0333Hauraki Gulf, New ZealandHit by ship, identified as pygmy blue
Lipton et al. (1995)25/11/1994 13.39.183379.4000Dhanushkodi, IndiaMeasured from snout to notch of caudal fluke
Van Waerebeek et al. (1997)7/2/1995Female18−33.9000−71.8333300 m north of mouth of Rapel River, ChileDecomposing
LeDuc et al. (1997)9/5/1995  −36.9833139.7000Australia 
Van Waerebeek et al. (1997)3/1/1997Female20.44−11.0393−77.6597Isla don Martin, Peru 
R. C. Anderson, unpubl.5/1/1997 163.250073.5000V. Rakeedhoo, MaldivesFloating at sea. Mandibles (longest 482 cm) and scapula on island
Anderson et al. (1999)20/1/1997 182.250073.3000Th. Guraidhoo, floating in Veimandhoo Kandu, MaldivesApproximate length
Van Waerebeek et al. (1997)20/3/1997 23−41.1667−73.9050Near Llico Bajo, X Region, Chile 
Anderson et al. (1999)3/1/1999 196.200073.0333Sh. Medukumburudhoo, washed on beach, Maldives 
A. D. Ilangakoon, unpubl.21/7/1999Female21.9–23.85.961280.4288Kaparatota/Weligama (south coast) Sri Lanka 
McCauley et al. (2004)6/11/2000 21−13.7500126.1330Troughton Island, Kimberleys, Australia 
A. N. Baker, unpubl.14/11/2001Female15.2−34.6333173.0167Henderson Bay, New ZealandPygmy blue?
McCauley et al. (2004), K. C. S. Jenner, unpubl.9/12/2001 22.3−34.0881114.9989Cape Freycinet, Western Australia, AustraliaID as pygmy blue whale; location incorrectly reported as Margaret River
Borsa & Hoarau (2004), Borsa (2006)29/1/2002Male16.5−22.3333166.8167Baie de la Somme, New Caledonia 
R. C. Anderson, unpubl.9/12/2002 154.166773.5167SW outer reef, K. Malé, MaldivesRotten, most of head missing, vertebral epiphyses not fully fused
Krishnan et al. (2004)21/12/2001 12.313.300074.7000Beach of Guijerbettu, Udupi district, Karnataka, IndiaDorsal fin 1% of total length
A. D. Ilangakoon, unpubl.15/10/2003Female20.16.910379.8492Bambalapitiya/Colombo (west coast) Sri Lanka 
A. D. Ilangakoon, unpubl.2/4/2004Male19.8–21.36.941879.8597Colombo Harbor (west coast) Sri Lanka 
A. D. Ilangakoon, unpubl.11/7/2004 188.137779.7005Thalawila (north-west coast) Sri Lanka 
R. C. Anderson, unpubl.6/1/2005 234.250073.5500On outer reef, K. Furana, MaldivesRotten, tail and part of head missing, photos held at MRC
Hucke-Gaete et al. (2005); B. Galletti Vernazzani, unpubl.29/3/2005Male23 or 24.38−41.9861−74.0333Pumillahue Bay, NW Chiloé Island, Chile 
Bannister et al. (2005)16/12/2005Female20.8−32.0167115.4686Strickland Bay, Rottnest Island, Western AustraliaTail-anus/total length = 0.24, therefore likely a pygmy blue whale
R. C. Anderson, unpubl.19/12/2005 204.683373.4333K. Olhahahi, MaldivesPhotos held at MRC

APPENDIX 4

Details of blue whales marked and recaptured in the Southern Hemisphere, ordered by Discovery tag number. When two marks were recovered from one whale, they were both fired on the same day and at the same location, except for two instances detailed in the footnotes. Where the notes indicate ‘uncertain’, and probably in instances where length and sex were not recorded, the mark was recovered from the cooker, digester, boiler or stored meat. In such cases, a range of possible recapture locations and dates was often recorded and the central such position and date reported here. Code prefix ‘G’ indicates a German mark and ‘USSR’ a Soviet mark.

CodeMarked latitudeMarked longitudeMarked dateRecaptured latitudeRecaptured longitudeRecaptured dateSexLength at capture (m)Distance (km)Duration (days)Notes
  • *

    Mark latitude of 1229 was −54.6500.

  • †Mark longitude of 18194 was −80.8333 .

  • CL, corpora lutea count; EP, ear plug laminae.

656/1229*−54.7167−33.983326/12/1934−54.5000−34.316729/12/1934Female24.1323 
700−54.2500−33.966706/12/1934−54.1833−34.833311/12/1934Male23.8575 
825/853−54.9167−35.233330/11/1934−55.1333−34.533330/11/1934Male23.5510 
859−54.9000−35.233330/12/1934−54.5000−37.000028/11/19461224351 
903−54.0167−38.850012/01/1935−55.4000−33.783319/01/1935Female23.93607 
1123/1125−55.0000−34.333329/12/1934−62.3333−45.833312/01/1939Female25.310481475 
1245−54.8833−34.566727/12/1934−59.3833−9.366730/12/193915891829 
2026−57.433323.833314/12/1935−61.000087.000016/12/19363473368 
2525−56.666739.000005/12/1934−64.550022.833301/02/1937Female22.91236789 
2537−56.600035.750004/12/1934−57.616716.466722/12/1938Female25.511651479 
2548−58.350049.266708/12/1934−59.000034.250002/12/1937Male24.48691090 
2816−63.350053.533317/01/1935−64.000090.000009/03/19361774417 
2892−63.533347.283322/01/1935−65.283384.500026/02/1936Male25.91770400 
2902−63.533347.950022/01/1935−66.000015.000012/03/1935156649 
2903−63.533347.950022/01/1935−63.933345.933326/01/1935Male26.21094 
2910−62.750046.366724/01/1935−63.416745.933326/01/1935Female21772 
2960/2965−62.766743.083326/01/1935−64.766741.416731/01/1935Female22.12375 
2963−62.650043.966726/01/1935−62.650034.883308/02/1935Female25.946313 
3013−61.916743.283328/01/1935−64.233329.750027/03/1935Female22.972658 
3023−62.016743.350028/01/1935−63.616739.900009/01/1936250346 
3528−63.433326.183328/02/1935−64.450079.450017/01/1937Female22.62526689 
3598−63.38338.300008/03/1935−60.000032.000020/01/194812964701 
3771−54.1833−39.250004/12/1935−54.8667−32.683314/11/1936Male24.2430346 
3853−56.1333−36.016711/12/1935−63.3667−47.116707/03/1936Female22.6101387 
4122−57.2833−33.916727/12/1935−54.5667−33.700030/12/19353023 
4563−55.3167−36.650002/01/1936−59.7333−29.766702/02/1936Male22.963931 
4843−54.8667−33.733318/01/1936−55.2333−34.250022/01/1936524 
5245−62.133387.616701/02/1936−63.916787.466708/02/1936Female26.81987 
5261−61.933388.700001/02/1936−61.866782.950002/01/1938Female25.9301701 
5456−63.950099.316713/02/1936−56.633312.350009/01/1948Female27.744744348Pregnant
5525−63.250094.316716/02/1936−63.733394.416717/02/1936Female25.3541 
5632−63.750081.850022/02/1936−57.383331.666720/12/1947Female27514319Pregnant
5728−63.816754.400002/03/1936−56.800017.033308/01/19372161312 
5800−64.400045.816708/03/1936−63.233372.366703/01/1938Female23.51299666 
7705−54.900024.816713/12/1936−61.116720.833309/02/1937Female24.472958 
8743−64.866730.700013/02/1937−55.500027.500015/12/194710553957Uncertain
10427/10431−55.8167−0.233317/12/1937−55.2000−35.400024/02/1939Female22.12190434 
10638−58.8000−31.366701/01/1938−61.2500−20.350009/01/1938Male22.96688 
11354−61.500054.833307/01/1953−68.633317.283318/03/19541890435 
12186−56.4667−6.950029/11/1953−54.5000−37.000023/03/19541889114 
12362−57.3667−32.600023/12/1953−60.0000−41.000020/01/195456628Uncertain
12363−57.6333−32.700023/12/1953−61.3000−31.433316/02/1954Male23.241455 
12391−59.8833−37.250010/12/1953−68.3333−15.500012/03/1954Male23.2139992 
12438−53.91678.666729/11/1954−62.1000−12.000021/02/19561508449 
12770−58.783342.250003/11/1955−65.183382.366703/03/1957Female24.12168486 
12777−57.766739.916704/11/1955−69.216717.000009/03/19571686491Uncertain
12826−54.400024.566710/11/1955−69.00004.000014/02/19571930462Uncertain
13147−62.9500−38.033316/11/1955−65.0500−26.866718/02/195659194 
13400−60.316755.200002/12/1957−64.400048.816703/02/1959Female24.7560428 
14645−64.5000−157.683305/01/1956−68.2833−125.883307/02/1958Male23.21458764Uncertain
14661−62.7667−127.083309/12/1955−66.2667−148.116717/02/1957Female22.91072436CL 0 EP 7
14730−62.783360.000017/12/1955−67.4000−127.416722/02/1958Male22.35523798 
15216−59.400041.216702/11/1955−61.6167−8.150017/02/1956Male21.32646107 
17406−60.2500139.000001/01/1957−70.7167161.133312/03/1959Female21.31529800 
17629−67.3000−82.333322/12/1956−67.7333−89.983302/02/1957Female23.532842 
17644−65.7000−85.333323/12/1956−66.3333−122.416702/02/1957Female23.2165241CL 0 EP 7
17645−65.4667−87.833323/12/1956−72.3333−156.000018/02/19582665422 
17745−66.6500−89.066703/01/1957−66.2000−95.783301/02/1957Male2530329 
17866−65.8500−92.633320/12/1956−66.0000−95.000001/02/1957Male24.710943 
18027−65.2000−179.316702/12/1957−65.866748.566722/03/196249431571Uncertain
18085−64.8833−164.066704/12/1957−67.1667168.583314/02/1959Female25.61250437CL 19
18155/18194−65.5500−80.800023/12/1957−69.0167−132.400008/02/1958Female21.9217947 
18163−65.5500−80.800023/12/1957−57.900087.750027/02/1962Male24.162501527EP 12
18166−65.4333−81.000023/12/1957−69.0000−96.633323/02/1958Male22.377862 
18235−65.8833−73.866702/01/1957−67.5000−128.333309/02/1957232438 
18318−64.2667155.733330/12/1957−63.766785.066712/02/1959Male21.93262409 
18323−64.0333156.033330/12/1957−67.6167162.916709/02/1958Male22.950641 
18981−61.0833−56.333320/12/1956−67.3167−132.783304/02/1957Female21.6351646CL 0
19705/19719−60.233360.166721/12/1957−63.500099.500015/02/1958Female20.7205856 
19720/19728−60.950057.833321/12/1957−61.516770.000005/02/1959Male23.5653411 
19754−61.316754.833322/12/1957−64.233316.766702/02/1958Female193242 
19762−60.866754.500024/12/1957−66.000040.000015/02/1959915418 
19766−60.900051.366723/12/1957−64.7500−15.750025/02/1958327064Uncertain
19768−60.866754.500024/12/1957−63.116794.483313/02/1958Male21.9206751 
19772−60.850054.466724/12/1957−62.500084.500015/02/1958157953Uncertain
19792−60.983355.266724/12/1957−64.850019.800006/02/1958Female21.3181944 
19798−61.316755.633324/12/1957−62.500084.500015/02/1958150353Uncertain
19799−60.983355.400024/12/1957−55.083335.350020/03/196213421547 
19834−67.3000171.133315/12/1957−64.5000136.000020/02/1959Male22.91601432 
20512−65.2000157.083319/12/1958−65.6667139.833308/02/1959Male23.879651 
20515−65.2333157.033319/12/1958−64.4167123.500013/02/1959Female23.8156956EP 7
22321−63.0667137.016716/12/1959−57.333395.666704/02/1960Male22.9232550EP 11
22543−59.333383.766722/12/1959−58.850073.533304/02/1960Male21.958644EP 11
24027−55.766780.216715/12/1960−60.850038.9167>05/03/19622432>445‘1961/62’
24535−58.966738.600019/12/1960−67.1333−3.583321/02/1961Female24.7225464 
25576−56.250049.050001/12/1962−43.916750.033304/04/1963Male21.51372124Pygmy, testes 16.0 kg, 14.5 kg
25605/25607−59.383366.766723/11/1962−54.583336.433305/03/1964Female24.21894468CL 0 EP 10
G01111−63.000025.750018/02/1939−63.833333.666712/01/1940Male19.5404328 
G01201−59.000030.000007/12/1938−64.900062.383302/01/1951Female27.417904409Pregnant
G01305−60.833331.833331/12/1938−60.400030.516702/01/1939862 
G01306−65.000035.000009/02/1939−65.450028.150006/03/193932325 
G01309−59.416733.833306/12/1938−61.400036.900020/12/1938Female25.327714 
G01370−65.233335.000026/02/1939−65.450028.483306/03/19393038 
USSR-25601−59.383366.766723/11/1962−63.500026.083302/01/1967Male 21701501 
USSR-25608−59.383366.766723/11/1962−63.616726.166702/01/1967Female 21641501 
USSR-25619−59.133368.333323/11/1962−59.600054.366710/01/1963Female 79148 

APPENDIX 5

List of sources for acoustic detections of blue whales in the study region. The reference, region (positions rounded to whole degrees), call type, recording method and dates are listed. Where sources are ‘unpubl.’ this is shorthand for ‘unpublished data’.

SourceRegionCall typeRecording methodRecording durationDates calls recorded
Alling et al. (1991)East coast, Sri LankaSri LankaDipping hydrophoneFeb–Apr 1984Feb–Apr 1984
C. W. Clark & A. R. Martin, pers. comm.South Georgia 54°S 38°WAntarcticMoored instrument4–5 Apr 20044–5 Apr 2004
Cummings & Thompson (1971)Guafo Island, ChileSouth-east PacificDipping hydrophone30–31 May 197030–31 May 1970
Ensor et al. (1999), Clark & Fowler (2001)Antarctica Areas III, IVAntarcticSonobuoyJan–Feb 199910, 15, 25 Jan; 4, 9, 21 Feb 1999
Ensor et al. (2000), D. Ljungblad, unpubl.Antarctica Area I 67–71°WAntarcticSonobuoyJan–Feb 200026 Jan; 11 Feb 2000
Ensor et al. (2004)Antarctica Area V 175°W−175°EAntarcticSonobuoyJan–Feb 200419 Jan; 7–21 Feb 2004
Ensor et al. (2006)Antarctica Area III 0–20°EAntarcticSonobuoy18 Jan−13 Feb 200618 Jan−13 Feb 2006
Kibblewhite et al. (1967)Three Kings Island, New ZealandNew ZealandMoored instrument1 day; date unknownUnknown
Ljungblad et al. (1998)Antarctic area IIAntarcticSonobuoy7 Jan−26 Feb 199729–30 Jan 1997
Ljungblad et al. (1998)Madagascar Plateau 25–35°S 40–45°EMadagascarSonobuoy7–28 Dec 199628 Dec 1996
McCauley et al. (2004)Cape Leeuwin, AustraliaAntarcticMoored instrumentOct 2002–Jul 2004May–Oct 2002−04
McCauley et al. (2004)Cape Leeuwin, AustraliaAustralianMoored instrumentOct 2002–Jul 2004Nov–Jun 2002−04
R. D. McCauley, unpubl.Bass Strait 40°S 145°ENew ZealandMoored instrumentMar–Aug 2002Jun 2002
R. D. McCauley, unpubl.Bass Strait 40°S 145°EAustralianMoored instrumentMar–Aug 2002Jun 2002
R. D. McCauley, unpubl.Robe, South Australia 37°S 140°EAustralianMoored instrumentNov 2004–Jun 2005; Nov 2005–Jun 2006Jan–Apr 2005−06
R. D. McCauley, unpubl.Perth Canyon, Australia 32°S 115°EAustralianMoored instrumentJan 2000–Dec 2005Nov–Jun, 2000−05
R. D. McCauley, unpubl.Exmouth, Australia 21°S 114°EAustralianMoored instrumentOct 2003–Oct 2004Nov–Dec 2003, Jun 2004
McKay et al. (2005)East Antarctica 67°S 70°EAntarcticMoored instrumentFeb 2003–Jan 2004Year-round but peaks Apr–Jun, Nov
McDonald (2006)North Island, New ZealandAntarcticMoored instrumentJan–Dec 1997May–Jul 1997
McDonald (2006)North Island, New ZealandNew ZealandMoored instrumentJan–Dec 1997Once each in Jun, Jul, Sep, Dec 1997
T. F. Norris, unpubl.Islas Lobos De La Fuera, PeruSouth-east PacificSonobuoy2–3 Nov 20002–3 Nov 2000
Rankin et al. (2005)Antarctic area V 150°E−170°WAntarcticSonobuoy6–8, 21, 29, 31 Jan 20026–8, 21, 29, 31 Jan 2002
Rankin et al. (2005)Antarctic area V 130°E−150°EAntarcticSonobuoy23–24 Jan 200323–24 Jan 2003
Samaran et al. (2006)Crozet IslandAntarcticMoored instrumentMay 2003–Apr 2004Unknown
Samaran et al. (2006)Crozet IslandMadagascarMoored instrumentMay 2003–Apr 2004Unknown
Širovićet al. (2004)Western Antarctic PeninsulaAntarcticMoored arrayMar 2001–Feb 2003Year-round but peaks Mar–Apr, Oct–Nov
Stafford et al. (1999)Eastern tropical Pacific 8°S 95°WSouth-east PacificMoored instrumentMay 1996–May 1997Year-round but peaks Mar–Aug
Stafford et al. (1999)Eastern tropical Pacific 8°S 95°WAntarcticMoored instrumentMay 1996–May 1997Jul 1996
Stafford et al. (2004)Eastern tropical Pacific 8°S 95°WAntarcticMoored instrumentMay 1996–Nov 2002Jun–Sep, peaks in Jul
Stafford et al. (2004)Indian Ocean Diego GarciaAntarcticMoored instrumentJan 2002–Apr 2003May–Aug, peaks in Jul
Stafford et al. (2004)Indian Ocean Cape LeeuwinAntarcticMoored instrumentJan 2002–Apr 2003May–Nov, peaks in Jul
Stafford et al. (2005)Indian Ocean Diego GarciaMadagascarMoored instrumentJan 2002–Apr 2003May–Jul, peak in Jul
Stafford et al. (2005)Indian Ocean Diego GarciaSri LankaMoored instrumentJan 2002–Apr 2003May–Jan
Stafford et al. (2005)Indian Ocean Cape LeeuwinAustraliaMoored instrumentJan 2002–Apr 2003Dec–Jun