Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 March 2021 | 13(3): 17875–17888
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.6483.13.3.17875-17888
#6483 | Received 29 July 2020 | Final
received 23 December 2020 | Finally accepted 19 February 2021
First
confirmed sightings of Blue Whales Balaenoptera
musculus Linnaeus, 1758
(Mammalia: Cetartiodactyla:
Balaenopteridae) in the Philippines since the 19th
century
Jo Marie Vera Acebes
1, Joshua Neal Silberg 2, Timothy
John Gardner 3, Edna Rex Sabater 4,
Angelico Jose Cavada Tiongson
5, Patricia Dumandan6, Diana Maria Margarita
Verdote7, Christine Louise Emata
8, Jean Utzurrum 9 & Arnel Andrew Yaptinchay 10
1,2,3,6,7 BALYENA.ORG, Paseo
del Mar, Brgy. Pangdan, Jagna 6308, Bohol, Philippines.
1 Zoology Division, National Museum
of the Philippines, Padre Burgos Drive, Rizal Park, Manila 1000, Philippines.
2 LAMAVE (Large Marine Vertebrates
Institute Philippines), Tejero, Jagna
6308, Bohol, Philippines.
4 210 F.W. Olin Bldg,
Department of Ocean Engineering and Marine Sciences, Florida Institute of
Technology, 150 W University Blvd, Melbourne FL 32901 USA.
4,5,8,9 Silliman University, Institute of
Environmental and Marine Sciences, Brgy, Bantayan, Dumaguete City 6200, Negros Oriental,
Philippines.
10 Marine Wildlife Watch of the
Philippines, 2108 Volta St., Makati City 1234, Philippines.
1 jmvacebes@yahoo.com
(corresponding author), 2 joshsilberg@gmail.com, 3 timjgard@gmail.com,
4 ersabater@gmail.com,
5 angelicoctiongson@su.edu.ph, 6
pdumandan@ufl.edu, 7 maitaverdote@gmail.com, 8 christinelouisemata@gmail.com,
9 jeanutz@gmail.com, 10 aayaptinchay@gmail.com
Editor: Anonymity requested. Date of publication: 26 March 2021 (online & print)
Citation: Acebes, J.M.V., J.N. Silberg, T.J. Gardner, E.R. Sabater,
A.J.C. Tiongson, P. Dumandan,
D.M.M. Verdote, C.L. Emata,
J. Utzurrum & A.A. Yaptinchay
(2021). First confirmed
sightings of Blue Whales Balaenoptera
musculus Linnaeus, 1758 (Mammalia: Cetartiodactyla:
Balaenopteridae) in the Philippines since the 19th
century. Journal of
Threatened Taxa 13(3):
17875–17888. https://doi.org/10.11609/jott.6483.13.3.17875-17888
Copyright: © Acebes et al. 2021. Creative Commons Attribution 4.0
International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: The National Geographic Society, EC-54888C-18; Society for Conservation Biology; BALYENA.ORG; U.S. Fulbright Program; Ocean Park Conservation Foundation - Hong Kong, FH01_11/12,
2011/12 (JNS); Rufford Small Grants Foundation RSGF Grant Number: 53.02.10 and 21574-2; Ocean Park Conservation Foundation - Hong Kong, MM08.1011,
2010/11 (ERS); Condura Run for the Dolphins (2012); SU-IEMS.
Competing interests: The authors declare no competing interests.
Author details: Jo
Marie Vera Acebes is a biologist, veterinarian
and conservationist working on marine mammals in the Philippines for over 20
years. She is the Founder and Principal Investigator of BALYENA.ORG. She is a
Fulbright Scholar, a National Geographic Explorer and a member of the
Philippine Aquatic Red List Committee – Subcommittee on Cetaceans. Joshua Neal Silberg
is a science advisor for LAMAVE. Timothy
John Gardner is a marine mammal researcher with BALYENA.ORG and was a
2017-2018 Fulbright U.S. Student Scholar to the Philippines. Edna Rex Sabater
is a Fulbright scholar and currently a Ph.D. candidate at Florida Institute of
Technology in Melbourne, FL USA. She specializes in population ecology, spatial
movement and foraging habits of cetaceans in the pelagic marine ecosystem using
stable isotopes and biotoxin analyses, and light microscopy. Angelico Jose Cavada Tiongson is a marine biologist with a special
interest in cetaceans and ecology. He is currently studying seagrasses and
small gobies for his MSc. Patricia Dumandan is a PhD student at the University of
Florida interested in quantitative and community ecology. Her research focuses
on understanding and predicting patterns in ecological systems using
trait-based approaches. Diana
“Maita” Verdote has an undergraduate degree in
Biology from the University of the Philippines in Mindanao. She has assisted
with various wildlife research projects in the Philippines. Christine Louise Emata
is a professional teacher and a Coastal Resource Management student of Silliman
University (sabbatical). She works closely with local government units, coastal
communities, and stakeholders. She specialised in designing curriculum for
environmental education and organising community activities related to
environmental conservation and protection. Jean
Utzurrum is a marine biologist currently
finishing her master’s degree in Silliman University, where her extensive field
research experiences include marine mammal research, coral reef restoration,
coral reef and mesophotic fishes, and coastal fisheries. She is also an
elasmobranch specialist for Marine Wildlife Watch of the Philippines. Arnel Andrew Yaptinchay
has been involved in marine biodiversity conservation in the Philippines for 30
years with a Doctor of Veterinary Medicine Degree from the University of the
Philippines and a MSc in Aquatic Tropical Ecology from Bremen University,
Germany. He’s the director of Marine Wildlife Watch of the Philippines and a
board member of BALYENA.ORG.
Author contribution: JMVA analysed the identification
photos, organized, participated in and took photographs for the boat-based
surveys for BALYENA.ORG, collated the reported and survey sightings information
and was a major contributor in writing and revising the manuscript. JNS
participated in and took photos for the LAMAVE surveys and was a major
contributor in writing the manuscript. TJG participated in the 2018 and 2019 surveys
for BALYENA.ORG and was a major contributor in revising the manuscript. ERS
organized, participated in and took photographs for the SU-IEMS surveys; made
the maps for the manuscript and contributed in revising the manuscript. AJCT
organized, participated in and took photographs for the SWIMS-HK survey. He
also participated in and took photographs for the BALYENA.ORG 2019 survey and
contributed in revising the manuscript. PD organized and participated in the
BALYENA.ORG 2017 survey. DMMV helped organize, participated in and took
photographs for the BALYENA.ORG 2017 survey. CLE helped organize and
participated in the LAMAVE 2010 survey and the SU-IEMS surveys. JU participated
in and took photographs for the BALYENA.ORG 2019 survey and the SU-IEMS surveys.
AAY helped collect reported sightings information from social media.
Acknowledgements: The National Geographic Society
funded the 2019 project: “In search of the lone Blue Whale in the Bohol Sea,
Philippines.” Research funding for the
2015, 2016, 2017, 2018, and 2019 BALYENA.ORG surveys was from contributions
from volunteers – Raphael Almendral, Carlo Roberto
Felix, Lorraine Lao, Sharon Lu, Marielle Panganiban, Michelle Relojas, Pierre Palallos, Luis
Benjamin Jurado, Serena Lagorio,
Alieth Bontuyan, Monika Jukubiak, Marcin Skowroński, Matt
Tacatani, Fiona Angana, Mariele Gepte, Julie Ann Butron, Vina Angelica Perducho,
Maita Beringuel, Kent Truog, Reina Castillo, Ivy Pangilinan, Anna Bianca Barrameda, Elaine Tacubanza,
Maude Lachaine, Paul Soliman, Pia Ronquillo, Aaron Roa, Cedric Valere, Roleen Sevillena, Rick Dane
Gomez, Dindo Karl Mari Malonzo,
and Paulina Ocampo. We also thank
BALYENA.ORG researchers Jesse Acebes, Zerlina Leung, Julia Motoomull,
Takeya Sakamoto, Elson Aca, Jerome Hulin, and Mark de la Paz. Thanks to the Society for Conservation
Biology Marine Section Conservation Research Small Grants Program for providing
funding for BALYENA.ORG’s 2017 survey.
LAMAVE research was supported through a grant from Ocean Park
Conservation Foundation – Hong Kong (J.S., A.P., K.P., FH01_11/12,
2011/12). We would like to thank
Alessandro Ponzo of LAMAVE and their volunteers:
Kristina Pahang, Dominic Clarke, Valeria Senigaglia,
Caitlin Birdsall, Katie Hughes, Julissah Evangelio, and Gary Haskins. This research was also
supported by the Rufford Small Grants Foundation
(2010), Ocean Park Conservation Foundation – Hong Kong (OPCF-HK) (2010-2011), Condura Run for the Dolphins (2012), and SU-IEMS through
E.R.S. The following are acknowledged
for their support and assistance: The Swire Institute of Marine Science (SWIMS)
at the University of Hong Kong, Institute of Environmental and Marine Sciences
(IEMS) at Silliman University, Janet Estacion, Leszek
Karczmarski, Dioscoro Inocencio, Ramon Raymundo, and Hans Seiter. The Dumaguete survey was conducted from
internal funding of SWIMS-HKU to the Cetacean Ecology Lab. We thank the Local Government Units of Jagna, Baclayon, Panglao and Lila in Bohol.
Support for the work of J.M.V.A. was provided by the Asia Research
Centre – Murdoch University in Western Australia, BALYENA.ORG and the National
Museum of the Philippines. Support for
the work of T.J.G. was provided by the U.S. Fulbright Program and BALYENA.ORG. We are grateful to Dr.
Chandra Salgado- Kent for her time and effort in making an informal comparison
of our photo with the SHBW Catalogue. We
thank Serhii Dashko for
helping with our figures. Thanks to Joselino Baritua of Pamilacan Island Dolphin and Whale Watching Tours. We also thank Bill Perrin, Louella Dolar, Lory Tan, Pet Digdigan,
Virginia Montgomery, Shelby Guigerre, Ferdinand Recio, GMA’s Born-To-Be-Wild crew, Mr. Eulo
Valeroso, Louise Dixon, Saturnina Quilas,
Zita Lin, the Sports Unlimited TV crew, Suzette Pepito, Nemesia Pingkian, Justin Jordan Reloj,
Danny Ocampo, Joseph Jasper Acay, Lyka
Marie Abella, GB Aguilar, Harold Biglete,
Judalyn Flores Partlow, Rico Ramos, Eric Rosenblad, Aissa Domingo, Manong Sany Baugbog,
Jefrey Enas, Manong Roel, and Manong Neil; the
Department of Agriculture - Bureau of Fisheries and Aquatic Resources.
Abstract: For over two centuries there were
no records of Blue Whales Balaenoptera
musculus in the Philippines. Whalers recorded Blue Whales in the
Philippines in the 19th century, and the next confirmed sighting in
the country was of a mother and calf in 2004.
Since then 33 subsequent Blue Whale sightings of potentially one
individual were recorded between 2004 and 2019, all within the central region
of the Philippines around the Bohol Sea.
This individual, recognized through photo-identification, was sighted on
at least 13 occasions during eight different years: 2010, 2011, 2012, 2015,
2016, 2017, 2018, and 2019. The
geographic location and timing of the sightings (January to July) suggest that
Blue Whales in the Philippines may extend the outer range edge of the
Indo-Australian population that migrate between western Australia, Indonesia,
and East Timor. Blue Whale sightings in
the Bohol Sea coincide with times of high ocean productivity, although further
investigation is needed to determine if they are actually feeding in this
region. Acoustic studies and
photo-identification matching with other Blue Whale catalogues will clarify the
stock identity of Blue Whales in the Philippines and their relation to the rest
of the Blue Whale population, with implications for the conservation of this
endangered species across multiple jurisdictions.
Keywords: Bohol Sea, photo-identification,
survey.
Abbreviations: ENP—Eastern North Pacific |
GPS—Geographic Positioning System | IUCN—International Union for the
Conservation of Nature | LAMAVE—Large Marine Vertebrates Institute Philippines
| PCBs—Polychlorinated Biphenyls | SHBWP—Southern Hemisphere Blue Whale
Photo-ID | SLR—Single Lens Reflex | SU-IEMS—Silliman University - Institute of
Environmental and Marine Sciences | SWIMS-HK—Swire Institute of Marine Science
of the University of Hong Kong | WNP—Western North Pacific.
INTRODUCTION
Blue Whales Balaenoptera
musculus Linnaeus, 1758 are currently classified as Endangered by the
International Union for the Conservation of Nature (IUCN) (Cooke 2018), and
sightings in the Philippines are rare.
Although historical data suggests Blue Whales occurred in Philippine
waters (Acebes 2014), their presence was not reported
between the end of the 19th century (1870) and 2004. Stories from fishers from Bohol suggest
sightings of mother-calf pairs in the early 1990s (Jo Marie V. Acebes pers. comm. 8.xi.2011). While a whale skull of unknown source labeled “Blue Whale” was once displayed on the grounds of a
village town hall in Lila, Bohol,
the evidence of Blue Whale occurrence in the 20th century remains
anecdotal (Acebes 2013). The first confirmed documentation of a Blue
Whale in the Philippines occurred when a mother and calf were filmed off Pamilacan Island in the Bohol Sea in February 2004 (Dolar & Sabater 2012; Acebes 2014). The
animal was initially thought to be a Bryde’s Whale Balaenoptera edeni
Anderson, 1879, but was subsequently identified as a Blue Whale (Acebes 2006).
Photographs of a baleen whale seen in the same area in May 2004 were
also confirmed to be a Blue Whale (Sabater
2005). These sightings were brief and no
detailed information on the animal and its behavior were
recorded.
With such a gap in time between records, the
subspecies and population of the Blue Whale seen in 2004 was unclear. There are four recognized subspecies of Blue
Whale (Committee on Taxonomy 2019); however, many authorities do not recognize
the northern Indian Ocean subspecies Balaenoptera
musculus indica (Blyth, 1859) as separate from
Pygmy Blue Whales Balaenoptera musculus brevicauda (Ichihara, 1966) because of a lack of
morphological differences (Branch et al. 2007b; Branch & Mikhalev 2008; Jefferson et al. 2015). Antarctic Blue Whales (Balaenoptera
musculus intermedia Burmeister, 1871) are restricted to Antarctic waters
south of 60°S and are morphologically and genetically distinct from other
subspecies (Rice 1998; Kato et al. 2002; Branch et al. 2007a,b; LeDuc et al. 2007; Branch & Mikhalev
2008; Branch et al. 2009). Balaenoptera musculus musculus
(Linnaeus, 1758) are found only in the Northern Hemisphere and, while longer
and heavier than B.m. indica and B.m.
brevicauda, are still shorter and lighter than
B.m. intermedia (Jefferson et
al. 2015).
Populations of Blue Whales can also be separated
acoustically into at least 10 distinct populations (Rankin et al. 2005;
McDonald et al. 2006, 2009; Stafford et al. 2011; Širović
et al. 2018). The Philippines lie on the
edge of the North Indian, Southeast Indian, North Pacific, and Southern Ocean
acoustically-recognized populations.
The central Indian Ocean population (B.m. indica),
is found in highest concentrations around Sri Lanka and appears to be resident
in nature (de Vos et al. 2012, 2016), while at least some individuals from the
Southeast Indian population (currently identified as B.m.
brevicauda) undergo migrations from
western Australia to Indonesia, arriving by June (Branch et al. 2007b; Double
et al. 2014). North Pacific B.m. musculus are recognized as at
least two acoustically separate populations, the eastern North Pacific
population (ENP) and western North Pacific population (WNP), with almost none
sighted south of northeastern Japan for decades
(McDonald et al. 2006, 2009; Branch et al. 2019). The western North Pacific Blue Whales were
historically hunted as far south as Taiwan (Tomilin
1957; Stafford et al. 2001; Wang et al. 2001), but were virtually extirpated
from the southern part of their range, including southern Japan (National
Marine Fisheries Service 1998; Clapham et al. 1999; Gilpatrick
& Perryman 2008). Southern Ocean B.m. intermedia remain south of 52°S
during the austral summer, but their acoustic song is heard throughout the
Southern Hemisphere in the winter months (Stafford et al. 2004, 2011; Rankin et
al. 2005; McDonald et al. 2006, 2009; Branch et al. 2007b; Samaran et al.
2013, 2019; Shabangu et al. 2019). The Philippines is geographically situated
between the known ranges of B.m. brevicauda, B.m.
indica, and B.m.
musculus subspecies, but is closest to the Southeast Indian Ocean
population of B.m. brevicauda. Since sub-specific taxonomy remains
unresolved (Cooke 2018) (See Fig. 1), we consider all Blue Whale sightings here
to be B. musculus sp.
We describe all documented encounters with Blue Whales
in the Philippines since 2004. We
investigate the distribution and ecology of Blue Whales in the Philippines by
reviewing the timing and location of these sightings and examining the behavior of animals encountered, and photographically
identifying the whales to initiate a photo-identification catalogue for the country.
MATERIALS AND METHODS
Study site
The primary study site was the Bohol Sea, also known
as the Mindanao Sea (Fig. 2). The Bohol
Sea is located in the central Philippines (9˚N & 124˚E) and is surrounded
by the island of Bohol in the north, southern Leyte in the east, and northwestern Mindanao in the south. It covers 29,000km² and measures 270km east
to west (Indab & Suarez-Aspilla
2004; Green et al. 2004). Located in the
centre of the Philippine archipelago, the Bohol Sea connects to the Sulu Sea to
the west and to the Pacific Ocean in the east.
Because the Bohol Sea has a relatively short continental shelf, there is
considerable pelagic ocean habitat close to the shores of the surrounding
islands — distinctive bathymetric conditions that contribute to deep water
upwelling and associated high primary productivity (Cabrera et al. 2011; Gordon
et al. 2011), and are similar to regions favored by
Blue Whales off California and Australia.
Cetaceans in the Bohol Sea are relatively understudied compared to
cetaceans in other areas of the Philippines, owing to the sea’s large
area. Confirmed sightings of B. musculus
sp. in the Philippines since 2004 have all been in the Bohol Sea region.
Sighting reports review
We collected and reviewed reports of sightings of Blue
Whales and other large baleen whales in local news and social media, and
examined photographs and videos to verify the species by looking for
distinctive characteristics. Other
photos and videos of large baleen whales submitted to the authors were included
when quality was sufficient to verify that it was a Blue Whale. We counted separate encounters of the same
individual whale on one day as a single sighting.
Blue Whales were morphologically distinguished from
other baleen whales through several distinctive characteristics: 1) the “splash
guard” or the prominent fleshy ridge anterior to the blowhole; 2) the large,
broad, U-shaped head; 3) the relatively small dorsal fin positioned far back on
the body; and 4) the mottled pigmentation in light and dark shades of gray found dorsoventrally along the body of the animal
except the head and fluke (Sears 2002).
Out at sea on a calm day from a distance, a Blue Whale projects a tall,
dense, broad blow which can also be used to distinguish it from the Fin Whale Balaenoptera physalus Linnaeus,
1758.
Small vessel-based surveys
Small vessel surveys were conducted in the Bohol Sea
between 2010 and 2019 by four different research groups (described further
below, for a summary see Table 1 and Fig. 2).
In all surveys, cetacean encounters were documented by recording the
species, pod composition, number, and behaviour. We used a handheld Geographic Positioning
System (GPS) to record the location of sightings. We photographed all cetacean species
encountered, and estimated the sizes of animals using known boat length, when
possible.
The Institute of Environmental & Marine Sciences
of Silliman University (SU-IEMS) conducted systematic line-transect surveys
using the distance sampling technique (Buckland et al. 2001), between June 2010
and June 2014 in the northwestern Bohol Sea using 20m
long outrigger boats (See Table 1 and Fig. 2).
Equal-distance zigzag design was followed. Transect legs were 20–25 km in length, 10km
apart at the base, covering an area of 766km².
This survey was strategically developed to investigate cetacean
distribution and abundance in the study area over time.
The Large Marine Vertebrates Institute Philippines
(LAMAVE) conducted non-systematic, non-random surveys in the northeastern Bohol Sea and the area around Pamilacan Island using 7–10 m long outrigger boats. The primary objective of these surveys was to
photo-identify Melon-headed Whales Peponocephala
electra (Gray, 1846),
hence the search pattern was set to maximize these sightings by searching
between three and 25km from shore across depths ranging between 200 and 2,000
m. In addition, if there were local
reports of large whales in the area, a survey was conducted as soon as
possible.
BALYENA.ORG conducted strip transect surveys in the
northern Bohol Sea from Anda in the East to Valencia
in the West, including the area around Pamilacan
Island using an 18–20 m long outrigger boat from 2015 to 2019 (see Table 1 for
details). The transect lines were set at
1km from the coastline, radiating five to 6km out and were approximately 1km
apart. Opportunistic surveys were
conducted in July 2017, January 2018, and March 2019 around Pamilacan
Island when Blue Whale sightings were reported.
An opportunistic survey was conducted by a team from
the Swire Institute of Marine Science of the University of Hong Kong
(SWIMS-HKU) along the southern coast of Negros Oriental in May 2016 after
receiving reports of a sighting of a Blue Whale in the area. An inflatable rubber boat about five to 7m
long with a 25hp engine was used to survey along the coast about one to two
kilometres from shore.
Photographic identification
We used 35mm digital single lens reflex (SLR) cameras
with 70–400 mm zoom lenses. We
photo-identified the animals using standard techniques used for Blue Whales
(Sears 1990; Calambokidis & Barlow 2004; Gendron
& De La Cruz 2012). We photographed
both sides of the flank from a perpendicular angle, and included the dorsal fin
as a point of reference. As much as
possible, we photographed the entire flank of the animal in one sequence as the
whale rounded out to dive. We also
photographed the head and fluke. We used
photographs of the fluke as part of the identification whenever possible. Photographs were considered good for
photo-identification based on the sharpness of the image, the lighting and if
the image was large enough for the markings to be clearly seen (Sears 1990). We compared good quality photographs taken of
Blue Whales encountered with the BALYENA.ORG catalogue, and conducted an
informal comparison with Geographe Bay and New
Zealand photos included in the Southern Hemisphere Blue Whale Photo-ID (SHBWP)
Catalogue (e.g., Galletti-Vernazzani et al. 2019),
which included left-side comparisons with 74 images (Chandra Salgado-Kent pers.
comm. 13.iv.2019).
RESULTS
Reported sightings in local news and social media
A total of 23 Blue Whale sightings were reported since
2004 based on reports in the local news and social media (Table 2). All reports were verified by examining the
photographs or videos. Although all the
photographs and videos examined were adequate for species identification, only
one was suitable for photo-identification.
Ten sightings occurred in the area off Pamilacan Island, while three occurred off Panglao Island, both in the province of Bohol (Fig.
3). Two sightings were observed off the
southern point of Sogod Bay in the province of
Southern Leyte at the far eastern edge of the Bohol Sea. One sighting was from Oslob
in southwestern Cebu, directly south-east of Bohol. Five sightings occurred off the coast of Dauin and Dumaguete in southwestern Negros Oriental, and an
additional two sightings were reported from Sipalay
and Hinoba-an along the southwestern shore of Negros
Occidental. All sightings were of a
solitary animal except for the first sighting in 2004, which was of a mom and
calf. No detailed description of the
behaviour was recorded because almost all sightings were made by tourists who
happened to be on a boat passing the area.
According to the local TV crew that documented the encounter with a Blue
Whale in March 2011, the whale excreted a reddish-brown liquid twice while they
were following it. The whale was
estimated to have a dive interval of 15 to 20 minutes.
The longest, almost continuous sighting of an
individual Blue Whale in the Philippines was in 2016, over 19 days from May to
June along the southern coasts of Negros Oriental and Occidental. Tracking the sighting locations within this
period seems to indicate that the whale was moving northwest, exiting the Bohol
Sea and traveling towards the Sulu Sea, as it was last sighted off the
southwestern coast of Negros Occidental.
Sightings from small vessel-based surveys
Eleven Blue Whale encounters were documented based on
small vessel surveys between 2010 and 2019 (Table 2). All sightings occurred in the area off Pamilacan Island, Bohol (Fig. 3) except for the 25 May 2016
sighting from the coast of Dumaguete City in southern Negros Oriental.
LAMAVE conducted surveys in 2010, 2011, 2012, and
2013. In 2010, 12 survey days were conducted between March and June. In 2011, 14 survey days were conducted from
April to June. In 2012, 21 survey days
were conducted from March to June. In
2013, 21 survey days were conducted from April to June. During all surveys, a Blue Whale was
encountered twice—June 2010 and March 2012 (Table 2).
SU-IEMS surveys were conducted in June 2010,
October-November 2010, April-May 2011, October 2011, March-April 2012, and
May-June 2014. The total effort was 58
survey days covering 766km² of the area.
No Blue Whales were encountered in any of the surveys but other balaenopterids
were seen.
The BALYENA.ORG surveys were conducted from 2015 to
2019 for a total of 67 combined dedicated strip-transect and opportunistic
survey days. Dedicated strip-transect
surveys during 61 days covered 1,191km² of area (Figure 2). A Blue Whale sighting was recorded on 25 May
2015 during the 2015 dedicated survey, but no Blue Whales were sighted during
the subsequent 2016 to 2019 dedicated surveys (See Table 2). Following reported Blue Whale sightings off
of Pamilacan Island, a Blue Whale was encountered on
19 and 21 July 2017; 26, 27, and 29 January 2018; and March 26, 2019 during
opportunistic surveys. On 29 January
2018, a Blue Whale was encountered twice, in the morning and afternoon.
On 25 May 2016, a large whale sighting was reported
off Dauin, Negros Oriental. A team from SWIMS-HKU headed southeast along
the coast of Dumaguete City and was able to locate the animal about 2km from
shore and confirmed the species as Blue Whale.
The team followed it for one hour and 11 minutes as it moved up and down
the coast off Bacong town and Dumaguete City before
eventually losing the animal due to unfavorable
conditions. The whale was sighted again
several hours later as close as 900m from shore. The whale was observed milling.
All individuals fit the description of ‘pygmy’ Blue
Whales by Kato et al. (2002) based on the body shape, coloration, dorsal hump,
and blowhole morphology. The individual
encountered in June 2010, May 2015, and May 2016 was estimated to be 20 to 22 m
long, while the individual encountered in 2012 and 2019 was estimated to be 19
to 20 m. The difference in size
estimation is most likely due to the subjectivity of observers.
All Blue Whales encountered during the surveys were
solitary. The whale encountered on 29
March 2012 was associated with Spinner Dolphins Stenella
longirostris.
At all encounters, except in May 2016, the whale appeared to be
resting. When approached, the whale swam
away or dove, resurfacing a hundred meters away or more from the research
boat. In 2015, the whale’s surface
interval was brief. Two or so breathing
bouts were observed, followed by a dive, and the whale would resurface 500m or
more away from the boat after the completion of its dive. In 2018, surface intervals were for
approximately one to five minutes, with about 10–15 breathing bouts, and the
whale resurfaced 500 or more meters away after the completion of its dive. In 2019, the surface interval was longer at
approximately nine to ten minutes, with about 10–14 breathing bouts.
Photographic identification
The photograph of the left flank of a Blue Whale taken
by the host of the local TV show on 2011 was compared with the photographs of
the Blue Whale encountered during the survey in 2010 and 2015, and was
confirmed to be the same individual.
Photographs of the left and right side of the Blue
Whale encountered in vessel-based surveys in 2010, 2012, 2015, 2016, 2017,
2018, and 2019 were taken. Based on
comparison of the photographs of the left side of the Blue Whales encountered
it was found that the same individual was photo-identified on 11 June 2010, 29
March 2012, 25 May 2015, 25 May 2016, and 21 July 2017 (Image 1). Closer examination of the photographs of the
left side of the dorsal fin of the blue whale encountered in 2010, 2012, 2015,
2016, 2017, and 2019 revealed an identical semi-circular indentation, which
further confirmed the identification (Image 2).
A good photograph of the ventral side of the fluke of the Blue Whale
encountered in May 2015, May 2016, January 2018, March 2018, and March 2019 was
also taken. Examination of the fluke
photos revealed identical notches on the left and right sides of the tip of the
fluke of all whales photographed (Image 3).
Results show that all 13 sightings of Blue Whales in eight different
years were of the same individual.
DISCUSSION
Despite the efforts of four research groups with an
accumulated effort of 194 days over 10 years between the months of January and
July, and between October and November, covering a total area of approximately
2,092km² of the northern Bohol Sea (Table 1 and Fig. 2), there was a paucity of
Blue Whale encounters. This suggests
that the species is not common in the region; however, given the size of the
area of the Bohol Sea, the combined survey effort of these groups was probably
not sufficient to cover the possible area of occurrence of the species. It must also be noted that most surveys were
not conducted consistently during the same month within the same area each
year, nor did they cover the entire month.
Although inconsistent, sightings of Blue Whales in the
Bohol Sea are significant because they represent the only area in the
Philippines that this Endangered species has been sighted and
photo-documented. Sightings reported and
recorded during the surveys were between the months of January and July, with
most sightings having occurred in May.
This coincides with local ecological knowledge about the seasonal
presence of large marine vertebrates in the Bohol Sea. According to local fishers and residents,
baleen whales come to the Bohol Sea between January and June with a peak from
March to May (Acebes 2013).
It is possible that baleen whales come to the Bohol
Sea to feed, as evidenced by their presence during the months of high
productivity and observations of former whale hunters (Acebes
2013). Blue Whale feeding is often
associated with coastal upwelling and other oceanographic features (Fiedler et
al. 1998; Palacios 1999; Gill 2002; Best et al. 2003; Etnoyer
et al. 2004, 2006; Croll & Marinovic
2005; Rennie et al. 2009). The Bohol
Sea’s connections with deep basins, the Pacific Ocean to the east and the Sulu
Sea in the west, give it “unique circulation and physicochemical properties”
(Cabrera et al. 2011). Furthermore, the
water movements—sea surface currents, formation of eddies, and entrainments—cause
upwelling and brings seasonal variations in productivity, food supply, and
subsequently, fish abundance in the Bohol Sea (Cabrera et al. 2011; Gordon et
al. 2011).
Some site fidelity exists, as evidenced by the
re-sighting of an individual Blue Whale 13 times between 2010 and 2019. Only one mother-calf pair has been recorded
in the Philippines (See Table 2). The
relatively low frequency of sightings suggests the area is unlikely to be a
prominent breeding ground similar to the situation in Chile (Hucke-Gaete et al. 2004).
There are still very limited sightings data to give any idea on the
movements or habitat-use of this Blue Whale in the Philippines.
The population identity of Philippine Blue Whales
remains unclear. The estimated size of
all of the encountered Blue Whales (≤ 22m) falls within the maximum length of B.m. brevicauda
(24.2 m) (Ichihara 1966; Omura 1984). The Philippines may represent a northward
extension of the Australia/Indonesia stock.
This is highly likely as Blue Whales have been reported in south-east
Asian waters in southern Indonesia between May and November (Kahn et al. 2000;
Branch et al. 2007b; Kahn 2007) and off Timor-Leste between September and
November (Dethmers et al. 2012). In 2006, one animal stranded in Sabah, Malaysia
(Ponnampalam 2012) suggesting that the stock range
may extend farther north. Recent
satellite telemetry studies indicate that Pygmy Blue Whales feeding off western
Australia migrate north to Indonesia, reaching the northern end of their
migration by June (Double et al. 2014).
It also showed that the Banda and Molucca Seas are potential breeding
grounds based on the timing of the movement of tagged Pygmy Blue Whales (Double
et al. 2014).
Other populations of Blue Whales inhabit the Indian
Ocean (Branch et al. 2007b). Acoustical
comparisons suggest that at least some of the Indian Ocean populations migrate
between Madagascar and Diego Garcia and between the Maldives/Sri Lanka and
Diego Garcia (Branch et al. 2007b). This
acoustical population has also been recorded off Crozet Island to the south (Samaran et al. 2010) and off Angola in southwestern Africa
(Cerchio et al. 2010; Figueiredo
& Weir 2014). The 2006 stranding in
Sabah, Malaysia (Ponnampalam 2012) could also have
belonged to this population. While
north-south migration has been noted within the Indian Ocean, no eastward
migration of Blue Whales has been recorded in the Andaman Sea, Malacca Strait,
or Gulf of Thailand.
Philippine Blue Whales may also belong to the mostly
extirpated western North Pacific stock owing to its proximity to Taiwan. The most recent record of a Blue Whale in
this region is a 20 m long carcass found on the beach of Taitung County, Taiwan
on 25 January 2020 (NAMR 2020). There
are no other records of sightings of Blue Whales between Taiwan and the central
Philippines. Blue Whale calls from the
western North Pacific are different than those from the eastern North Pacific
(Stafford et al. 2001; Monnahan et al. 2014) with
calls recorded least often in winter and spring, suggesting a possible
migration. Both vocalization types were
recorded in the central Pacific (Stafford et al. 2001) and have been noted from
Midway Island (Northrup et al. 1971).
It is important to gather additional data on the
species, given the existing threats to cetaceans in the region such as the risk
of entanglement with fishing gear and ship strike (Laist
et al. 2001; NOAA 2009; de Vos et al. 2016), especially around the busy
shipping lanes in the vicinity of Dumaguete City and Cebu, the third largest
city in the Philippines. The Bohol Sea
is one of the main fishing grounds in the Central Visayas
region (Green et al. 2004) where commercial and municipal fishing vessels may
potentially pose risk of gear entanglement to whales. Overfishing of high trophic level species in
the Bohol Sea (Lavides et al. 2010) may have unknown
impacts to large whales in the region by reducing predation on plankton-feeding
fish leading to increased competition for prey resources. Other unassessed anthropogenic threats in the
area include noise associated with shipping and seismic exploration (National
Marine Fisheries Service 1998; Di Iorio & Clark
2010; Melcón et al. 2012), pollutants such as
polychlorinated biphenyls (PCBs) and organochlorines (Metcalfe et al. 2004), and
unregulated dolphin and whale watching operations.
Blue Whales have been seen in the Philippines for the
first-time since the end of the 19th century. The re-sighting of a single animal on 13
occasions across eight years suggests potential site fidelity for at least
certain individuals. Acoustic studies
and increased photo-identification survey effort with matching with other Blue
Whale catalogues will help clarify the stock identity of Blue Whales in the
Philippines and their relation to the rest of the Blue Whale population. The timing of Blue Whale sightings in the
Bohol Sea coincides with sightings of the Indo-Australian Blue Whale population
and may represent an extension of the outer edge of this population’s range.
Longer, dedicated surveys must be conducted in the
areas in the Bohol Sea where these sightings occurred to determine the species’
habitat-use and distribution. Increased
survey effort all along the northern Bohol Sea and perhaps around the eastern
and western straits will help determine the regularity of occurrence of the
species in the region. Although
preliminary data indicate that occurrence of the Blue Whale coincides with the
areas and season of high productivity in the Bohol Sea, further investigation
is needed to validate that whales are feeding in these waters.
The confirmation of the presence of Blue Whales in the
Philippines contributes to our knowledge on the ecology and distribution of
this endangered species. It further
highlights the high marine biodiversity of the southeastern
Asian seas region and the Coral Triangle and the need for further research and
conservation in the region.
Table 1. Survey effort of different research groups
from 2010 to 2019.
|
Research Group |
Survey period |
No. of Days |
|
LAMAVE |
iii.2010 |
1 |
|
iv.2010 |
2 |
|
|
v.2010 |
8 |
|
|
11.vi.2010 |
1 |
|
|
iv.2011 |
4 |
|
|
v.2011 |
3 |
|
|
vi.2011 |
7 |
|
|
iii.2012 |
4 |
|
|
iv.2012 |
2 |
|
|
v.2012 |
13 |
|
|
vi.2012 |
2 |
|
|
iv.2013 |
4 |
|
|
v.2013 |
11 |
|
|
vi.2013 |
6 |
|
|
|
TOTAL |
68 |
|
SU-IEMS |
vi.2010 |
2 |
|
x.2010 |
4 |
|
|
xi.2010 |
10 |
|
|
iv.2011 |
15 |
|
|
v.2011 |
8 |
|
|
x.2011 |
2 |
|
|
iii.2012 |
2 |
|
|
iv.2012 |
6 |
|
|
v.2014 |
5 |
|
|
vi.2014 |
4 |
|
|
|
TOTAL |
58 |
|
BALYENA.ORG |
18–25.v.2015 |
9 |
|
19–27.v.2016 |
9 |
|
|
19–27.v.2017 |
9 |
|
|
19 & 21.vii.2017 |
2 |
|
|
26—29.i.2018 |
4 |
|
|
23.v–1.vi.2018 |
10 |
|
|
10–12.iii.2019 |
3 |
|
|
16—18.iii.2019 |
3 |
|
|
26—28.iii.2019 |
3 |
|
|
15–17.iv.2019 |
3 |
|
|
23–26.iv.2019 |
4 |
|
|
21–27.v.2019 |
7 |
|
|
22.vii.2019 |
1 |
|
|
|
TOTAL |
67 |
|
SWIMS-HKU |
25.v.2016 |
1 |
|
|
TOTAL |
1 |
Table 2. Confirmed sightings of blue whales in the
Philippines from 2004 to 2019.
|
Date sighted |
Reported sightings |
Location |
Estimated size (m) |
Group composition |
|
ii.2004 |
Sports Unlimited (local TV crew) |
Pamilacan Island |
- |
Mother and calf |
|
1.v.2004 |
Pet Digdigan &
Virginia Montgomery |
Pamilacan Island |
- |
single |
|
20.v.2008 |
Eulo Valeroso |
east of Pamilacan Island |
- |
single |
|
12.iii.2010 |
Louise Dixon |
Two nautical miles from Napantao,
east of Sogod Bay, So.
Leyte |
- |
single |
|
14.iii.2011 |
GMA Born-To-Be-Wild (local TV crew) |
Pamilacan Island |
25–30m |
single |
|
24.v.2015 |
Suzette Pepito |
Between Panglao Island and
Balicasag Island |
- |
single |
|
iii.2016 |
Jojo Baritua |
Pamilacan Island |
- |
single |
|
3.iv.2016 |
- |
Oslob, Cebu |
- |
single |
|
13–14.iv.2016 |
Nemesia Pingkian |
Pamilacan Island |
- |
single |
|
28.iv.2016 |
Justin Jordan Reloj |
Padre Burgos, So. Leyte |
- |
single |
|
17.v.2016 |
Danny Ocampo |
Canday-ong, Dumaguete, Negros Oriental |
- |
single |
|
20.v.2016 |
Joseph Jasper Acay |
Panglao Island |
- |
single |
|
23.v.2016 |
Lyka Marie Abella |
Dauin, Negros Oriental |
- |
single |
|
24–26.v.2016 |
GB Aguilar, Harold Biglete,
Judalyn Flores Partlow |
San Miguel, Bacong-Dumaguete
City, Negros Oriental |
- |
single |
|
29.v.2016 |
- |
Sipalay, Negros Occidental |
- |
single |
|
4.vi.2016 |
- |
Hinoba-an, Negros Occidental |
- |
single |
|
18.vii.2017 |
Manong Sonny |
off Pamilacan Island |
- |
single |
|
11.viii.2017 |
Rico Ramos |
5km off Dauin, Negros
Oriental |
- |
single |
|
1–5.iii.2018 |
Jojo Baritua |
off Pamilacan Island |
- |
single |
|
3.iii.2018 |
Jojo Baritua |
Cervera shoal, west of Pamilacan |
- |
single |
|
12–18.iii.2018 |
Jojo Baritua |
off Pamilacan Island |
- |
single |
|
22.iii.2018 |
Zita Lin |
off southern coast of Panglao |
- |
single |
|
10.iii.2019 |
Vanela Grace Torres |
off Dauin, Negros Oriental |
- |
single |
|
|
Survey sightings |
|
|
|
|
11.vi.2010 |
LAMAVE |
9.47835N & 123.94426E |
22m |
single |
|
29.iii.2012 |
LAMAVE |
Pamilacan Island |
19m |
single |
|
25.v.2015 |
BALYENA.ORG |
09.51238N & 124.11468E |
22m |
single |
|
25.v.2016 |
SWIMS-HKU |
09.26222N & 123.32779E |
20–21m |
single |
|
19.vii.2017 |
BALYENA.ORG |
9.53003N & 123.8391E |
less than 30m |
single |
|
21.vii.2017 |
BALYENA.ORG |
9.469N & 123.85447E |
less than 30m |
single |
|
26.i.2018 |
BALYENA.ORG |
9.516725N & 123.90106E |
Under 30m |
single |
|
27.i.2018 |
BALYENA.ORG |
9.47678N & 123.88336E |
Under 30m |
single |
|
29.i.2018 |
BALYENA.ORG |
9.54751N & 123.91459E |
Under 30m |
single |
|
29.i.2018 |
BALYENA.ORG |
9.5594N & 123.93287E |
Under 30m |
single |
|
26.iii.2019 |
BALYENA.ORG |
9.46154N & 123.87368E |
19–20m |
single |
For
figures & images - - click here
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