scholarly journals Seasonal Occurrence of Sympatric Blue Whale Subspecies: the Chilean and Southeast Indian Ocean Pygmy Blue Whales With the Antarctic Blue Whale

2021 ◽  
Vol 8 ◽  
Author(s):  
Gary Truong ◽  
Tracey L. Rogers
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Lower Latitude ◽  
Seasonal Patterns ◽  
Austral Winter ◽  
Blue Whale ◽  
Acoustic Data ◽  
The Pacific ◽  
The Antarctic ◽  
Blue Whales

There are multiple blue whale acoustic populations found across the Southern Hemisphere. The different subspecies of blue whales feed in separate areas, but during their migration to lower-latitude breeding areas each year, Antarctic blue whales become sympatric with pygmy and Chilean blue whales. Few studies have compared the degree of this overlap of the Southern Hemisphere blue whale subspecies across ocean basins during their migration. Using up to 16 years of acoustic data, this study compares the broad seasonal presence of Antarctic blue whales, Chilean blue whales, and Southeast Indian Ocean (SEIO) pygmy blue whales across the Pacific and Indian Oceans. Antarctic blue whales were sympatric with the other two blue whale subspecies during the migrating season of every year. Despite this overlap, Chilean and pygmy blue whale detections peaked earlier during the austral autumn (April–May) while Antarctic blue whale detections peaked later during the austral winter (June). Chilean (Pacific Ocean) and SEIO (Indian Ocean) pygmy blue whales showed similar seasonal patterns in detections despite occurring in different ocean basins. Though we have shown that Antarctic blue whales have the potential to encounter other blue whale subspecies during the breeding season, these distinct groups have remained acoustically stable through time. Further understanding of where these whales migrate will enable a better insight as to how these subspecies continue to remain separate.

scholarly journals Multiple pygmy blue whale acoustic populations in the Indian Ocean: whale song identifies a possible new population

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Emmanuelle C. Leroy ◽  
Jean-Yves Royer ◽  
Abigail Alling ◽  
Ben Maslen ◽  
Tracey L. Rogers
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Tropical Indian Ocean ◽  
Blue Whale ◽  
The North ◽  
Central Indian Ocean ◽  
Commercial Whaling ◽  
The Indian Ocean ◽  
And Migration ◽  
Blue Whales

AbstractBlue whales were brought to the edge of extinction by commercial whaling in the twentieth century and their recovery rate in the Southern Hemisphere has been slow; they remain endangered. Blue whales, although the largest animals on Earth, are difficult to study in the Southern Hemisphere, thus their population structure, distribution and migration remain poorly known. Fortunately, blue whales produce powerful and stereotyped songs, which prove an effective clue for monitoring their different ‘acoustic populations.’ The DGD-Chagos song has been previously reported in the central Indian Ocean. A comparison of this song with the pygmy blue and Omura’s whale songs shows that the Chagos song are likely produced by a distinct previously unknown pygmy blue whale population. These songs are a large part of the underwater soundscape in the tropical Indian Ocean and have been so for nearly two decades. Seasonal differences in song detections among our six recording sites suggest that the Chagos whales migrate from the eastern to western central Indian Ocean, around the Chagos Archipelago, then further east, up to the north of Western Australia, and possibly further north, as far as Sri Lanka. The Indian Ocean holds a greater diversity of blue whale populations than thought previously.

Seasonal climate summary for the southern hemisphere (spring 2016): strong negative Indian Ocean Dipole ends, bringing second wettest September to Australia

2019 ◽  
Vol 69 (1) ◽  
pp. 273
Author(s):  
Blair Trewin ◽  
Catherine Ganter
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Indian Ocean Dipole ◽  
Southern Oscillation ◽  
Sea Ice Extent ◽  
Antarctic Sea Ice ◽  
The Pacific ◽  
The Indian Ocean ◽  
Low Levels ◽  
Equatorial Climate

This summary looks at the southern hemisphere and equatorial climate patterns for spring 2016, with particular attention given to the Australasian and equatorial regions of the Pacific and Indian Ocean basins. Spring 2016 was marked by the later part of a strong negative phase of the Indian Ocean Dipole, alongside cool neutral El Niño–Southern Oscillation conditions. September was exceptionally wet over much of Australia, contributing to a wet spring with near-average temperatures. The spring was one of the warmest on record over the southern hemisphere as a whole, with Antarctic Sea ice extent dropping to record low levels for the season.

Opportunistic sightings of blue whales off Sydney, Australia

2021 ◽  
Author(s):  
Vanessa Pirotta ◽  
Robert Harcourt
Keyword(s):  
Marine Mammals ◽  
New South ◽  
Short Note ◽  
Balaenoptera Musculus ◽  
Blue Whale ◽  
South Wales ◽  
Tasman Sea ◽  
Migratory Movements ◽  
The Antarctic ◽  
Blue Whales

ABSTRACT Two subspecies of blue whale occur in Australian waters, (1) the pygmy blue whale (Balaenoptera musculus brevicauda) and (2) the Antarctic blue whale (Balaenoptera musculus intermedia). Understanding blue whale presence in Australian waters is critical to ensuring Australia’s protection of these marine mammals as both subspecies were heavily exploited during historical whaling. This short note documents pygmy blue whale sightings in New South Wales waters over the last 18 years. Observations were opportunistically made via citizen science and verified by scientists. Sightings in this note contribute to our limited knowledge of pygmy blue whale distribution along the east coast of Australia and may help understand the migratory movements of New Zealand pygmy blue whales off Australia and in the Tasman Sea. Overall, information presented in this note contributes to Australia’s national and international conservation efforts to protecting blue whales as a migratory and threatened species.

scholarly journals A Comparison of Southern Hemisphere Cyclone Track Climatology and Interannual Variability in Coarse-Gridded Reanalysis Datasets

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Timothy Paul Eichler ◽  
Jon Gottschalck
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Southern Hemisphere ◽  
Positive Trend ◽  
South American ◽  
Cyclone Track ◽  
Weather Forecasts ◽  
East Indian ◽  
The Pacific ◽  
Cyclone Tracks

Southern Hemisphere (SH) extratropical cyclones have received less study than their Northern Hemisphere (NH) counterparts. Generating SH cyclone tracks from global reanalysis datasets is problematic due to data reliability, especially prior to 1979. It is therefore prudent to compare the climatology and variability of SH cyclone tracks from different reanalysis datasets. We generate cyclone track frequency and intensity climatologies from three reanalysis datasets: The National Center for Environmental Prediction’s Reanalysis I and Reanalysis II datasets and the European Centre for Medium Range Weather Forecasts ERA-40 dataset. Our results show that ERA-40 produces more intense cyclones in the SH active cyclone region compared to NCEP reanalyses. More intense storms are also found in the SH active cyclone region in NCEP reanalyses data post-1979 reflecting the positive trend in the AAO in the past few decades. When evaluating interannual variability, our results show Rossby wave trains including the Pacific South American (PSA) and the East Indian Ocean pattern in response to anomalous heating linked to El Niño and the Indian Ocean Dipole (IOD), respectively. Response to the AAO shows a robust annular structure for cyclone track frequency, but not intensity suggesting a weak relationship between cyclone frequency and cyclone intensity.

scholarly journals Past and present distribution, densities and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean

Mammal Review ◽  
2007 ◽  
Vol 37 (2) ◽  
pp. 116-175 ◽  
Author(s):  
T. A. BRANCH ◽  
K. M. STAFFORD ◽  
D. M. PALACIOS ◽  
C. ALLISON ◽  
J. L. BANNISTER ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Balaenoptera Musculus ◽  
Northern Indian Ocean ◽  
Present Distribution ◽  
Blue Whales

GOME Observations of Stratospheric Trace Gas Distributions during the Splitting Vortex Event in the Antarctic Winter of 2002. Part I: Measurements

2005 ◽  
Vol 62 (3) ◽  
pp. 778-785 ◽  
Author(s):  
Andreas Richter ◽  
Folkard Wittrock ◽  
Mark Weber ◽  
Steffen Beirle ◽  
Sven Kühl ◽  
...  
Keyword(s):  
Time Series ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Trace Gas ◽  
Austral Winter ◽  
Situation Analysis ◽  
Ozone Destruction ◽  
Ozone Monitoring ◽  
The Antarctic

Abstract Measurements from the Global Ozone Monitoring Experiment (GOME) are used to study the chemical evolution of the stratosphere during the unusual 2002 winter in the Southern Hemisphere. The results show that chlorine activation as indicated by OClO columns was similar to previous years in the vortex until the major warming on 26 September 2002 after which it decreased rapidly. Similarly, NO2 columns were only slightly larger than in previous years before the warming, indicating strong denoxification and probably also denitrification. After the warming, very large NO2 columns were observed for a few days, which then decreased again as the vortex reestablished itself until the final warming. Ozone columns were much larger than in any previous year from September onward, mainly as a result of the unusual dynamical situation. Analysis of the global long-term time series of GOME measurements since 1996 provides a unique opportunity to set the austral winter 2002 into perspective. The GOME data reveal the large difference in variability of chlorine activation between the two hemispheres, whereas denoxification shows surprisingly little variation from year to year in both hemispheres. However, NO2 depletion in the Southern Hemisphere is usually sustained for about one month longer in the Antarctic stratosphere as a result of the stable vortex. Compared to the observations in the Northern Hemisphere, the austral winter 2002 was still stable and cold and had a high potential for chemical ozone destruction.

scholarly journals Body size data collected non-invasively from drone images indicate a morphologically distinct Chilean blue whale (Balaenoptera musculus) taxon

2020 ◽  
Vol 43 ◽  
pp. 291-304 ◽  
Author(s):  
MS Leslie ◽  
CM Perkins-Taylor ◽  
JW Durban ◽  
MJ Moore ◽  
CA Miller ◽  
...  
Keyword(s):  
Body Size ◽  
Southern Hemisphere ◽  
Body Length ◽  
Tail Length ◽  
Intraspecific Diversity ◽  
Conservation Strategies ◽  
Balaenoptera Musculus ◽  
Blue Whale ◽  
Blue Whales ◽  
Size Data

The blue whale Balaenoptera musculus (Linnaeus, 1758) was the target of intense commercial whaling in the 20th century, and current populations remain drastically below pre-whaling abundances. Reducing uncertainty in subspecific taxonomy would enable targeted conservation strategies for the recovery of unique intraspecific diversity. Currently, there are 2 named blue whale subspecies in the temperate to polar Southern Hemisphere: the Antarctic blue whale B. m. intermedia and the pygmy blue whale B. m. brevicauda. These subspecies have distinct morphologies, genetics, and acoustics. In 2019, the Society for Marine Mammalogy’s Committee on Taxonomy agreed that evidence supports a third (and presently unnamed) subspecies of Southern Hemisphere blue whale subspecies, the Chilean blue whale. Whaling data indicate that the Chilean blue whale is intermediate in body length between pygmy and Antarctic blue whales. We collected body size data from blue whales in the Gulfo Corcovado, Chile, during the austral summers of 2015 and 2017 using aerial photogrammetry from a remotely controlled drone to test the hypothesis that the Chilean blue whale is morphologically distinct from other Southern Hemisphere blue whale subspecies. We found the Chilean whale to be morphologically intermediate in both overall body length and relative tail length, thereby joining other diverse data in supporting the Chilean blue whale as a unique subspecific taxon. Additional photogrammetry studies of Antarctic, pygmy, and Chilean blue whales will help examine unique morphological variation within this species of conservation concern. To our knowledge, this is the first non-invasive small drone study to test a hypothesis for systematic biology.

scholarly journals A new blue whale song-type described for the Arabian Sea and Western Indian Ocean

2020 ◽  
Vol 43 ◽  
pp. 495-515
Author(s):  
S Cerchio ◽  
A Willson ◽  
EC Leroy ◽  
C Muirhead ◽  
S Al Harthi ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Arabian Sea ◽  
Western Indian Ocean ◽  
Small Population ◽  
Song Type ◽  
Blue Whale ◽  
Conservation Action ◽  
Status Assessment ◽  
The 1960S ◽  
Blue Whales

Blue whales Balaenoptera musculus in the Indian Ocean (IO) are currently thought to represent 2 or 3 subspecies (B. m. intermedia, B. m. brevicauda, B. m. indica), and believed to be structured into 4 populations, each with a diagnostic song-type. Here we describe a previously unreported song-type that implies the probable existence of a population that has been undetected or conflated with another population. The novel song-type was recorded off Oman in the northern IO/Arabian Sea, off the western Chagos Archipelago in the equatorial central IO, and off Madagascar in the southwestern IO. As this is the only blue whale song that has been identified in the western Arabian Sea, we label it the ‘Northwest Indian Ocean’ song-type to distinguish it from other regional song-types. Spatiotemporal variation suggested a distribution west of 70°E, with potential affinity for the northern IO/Arabian Sea, and only minor presence in the southwestern IO. Timing of presence off Oman suggested that intensive illegal Soviet whaling that took 1294 blue whales in the 1960s likely targeted this population, as opposed to the more widely distributed ‘Sri Lanka’ acoustic population as previously assumed. Based upon geographic distribution and potential aseasonal reproduction found in the Soviet catch data, we suggest that if there is a northern IO subspecies (B. m. indica), it is likely this population. Moreover, the potentially restricted range, intensive historic whaling, and the fact that the song-type has been previously undetected, suggests a small population that is in critical need of status assessment and conservation action.

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