Bohol Sea IMMA
Size in Square Kilometres
29 517 km2
Qualifying Species and Criteria
Sperm whale – Physeter macrocephalus
Blue whale – Balaenoptera musculus
Melon-headed whale – Peponocephala electra
Criterion B (2)
Fraser’s dolphin – Lagenodelphis hosei
Criterion B (2)
Marine Mammal Diversity
Criterion D (2)
Balaenoptera edeni, Balaenoptera omurai, Feresa attenuata, Grampus griseus,
Globicephala macrorhynchus, Kogia sima, Kogia breviceps, Mesoplodon densirostris,
Orcinus orca, Pseudorca crassidens, Stenella attenuata, Stenella longirostris longirostris, Stenella longirostris roseiventris, Steno bredanensis, Tursiops truncatus
MariDownload fact sheet
The Bohol Sea represents a biodiversity hotspot for cetaceans in the Philippines, and South East Asia where 19 species of cetaceans are known to occur, including the blue whale (Balaenoptera musculus). The Bohol Sea is the only known area in the country where blue whales have been positively identified. Balaenoptera edeni and Balaenoptera omurai are also known to occur here and were hunted until the late 1990s. Sperm whales have also been historically hunted in this area and sightings have been reported during dedicated surveys, public reports and strandings. Highly productive and deep waters support large populations of small resident teuthophagous odontocetes, including melon-headed whales, short-finned pilot whales, Risso’s dolphins and Fraser’s dolphins. The deep waters also host beaked whales and several encounters with Blainville’s beaked whale have been reported.
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
Based on logbook and museum records available from the whaling era, blue whales were historically present in the Philippines. Surveys conducted between 2000 and 2004 in the area by WWF-Philippines and Silliman University, did not report any baleen whales. However, informal reports from fishermen and dolphin watching tour operators in Pamilacan Island in the North Bohol Sea, describe the sporadic presence of large whales, locally known as bongkaras, between January and June. The first confirmed sighting of a blue whale (Balaenoptera musculus) in the Bohol Sea occurred in 2004 but it was not until 2010 that the species was properly documented and photo-identified. There have been 33 blue whale sightings recorded between 2004 and 2019, in the Bohol Sea (Acebes et al., 2021). One single individual blue whale, recognized through photo-identification, was re-sighted in the Bohol Sea during eight different years: 2010, 2011, 2012, 2015, 2016, 2017, 2018 and 2019 (Acebes et al., 2021). The geographic location and time of year—all sightings occurred between January and 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 (Acebes et al., 2021). Although blue whale sightings in the Bohol Sea coincide with times of high ocean productivity, further investigation is needed to determine if the whales are coming to the region to feed. Similarly, sightings of sperm whales have been uncommon but regular for the last fifteen years with reports from early WWF surveys, surveys carried out from Silliman University and BALYENA.ORG on the north-western Bohol Sea and from sightings of tourists.
Criterion B: Distribution and Abundance
Sub-criterion B2: Aggregations
During 84 surveys conducted by Ponzo and colleagues in the Northern Bohol Sea from 2010 to 2013, the melon-headed whale was the most encountered species 41.8% (n= 121), followed by Fraser’s dolphin and spinner dolphins. This shows similar findings as earlier surveys conducted by Sabater (2005) from 2002-2004 wherein the most frequently sighted species were the spinner dolphins, melon-headed whales and Fraser’s dolphins, and Tiongson and Sabater (2013) from 2010-2012 with the melon-headed whales and Fraser’s dolphins as the two most commonly encountered species. Based on dorsal fin markings, 415 unique individual melon-headed whales have been identified in this area with 59 individuals recaptured across years (from 2010 to 2013) and some individuals photographed in all 4 years, suggesting some degree of residency. Group size ranged from 1 to 70 individuals (median= 20; μ= 21) and on occasions, several groups converge in a 1km area and form mega pod of up to 400 individuals. Encounters with Fraser’s dolphins were in numbers of more than 18 animals and in mixed species group, the most frequent association was with melon-headed whales (Sabater 2005).
Sub-criterion D2: Diversity
The Bohol Sea hosts a diversity of cetaceans, with 19 species confirmed from sightings during survey, strandings or verified reports from tourists. From March 2010 to June 2013, a total of 12 species were encountered in the Bohol Sea (n= 291 sightings) by Ponzo and colleagues, with melon-headed whales was the most encountered species 41.8% (Peponocephala electra, n= 121) followed by Fraser’s dolphin 21.6 % (Lagenodelphis hosei, n= 63), spinner dolphins (Stenella longirostris, n= 41), pantropical spotted dolphins (Stenella attenuata, n= 2), bottlenose dolphins (Tursiops sp., n= 1), short-finned pilot whales (Globicephala macrorhynchus, n= 9), Risso’s dolphin (Grampus griseus, n= 8), dwarf sperm whale (Kogia sima, n= 5), Blainville beaked whales (Mesoplodon densirostris , n= 3), rough-toothed dolphin (Steno bredanensis, n= 1), Bryde’s whale (Balaenoptera edeni, n= 4), blue whale (Balaenoptera musculus, n= 2). Other species were encountered off effort, including pygmy killer whales (Feresa attenuata) and sperm whale (Physeter macrocephalus). Systematic boat surveys conducted by the Institute of Environmental and Marine Sciences, Silliman University between 2010-2012, recorded 11 cetacean species in which, five were seen in mixed-species groups of two or more species (Tiongson & Sabater 2014). Eight species were encountered, in decreasing frequency: melon-headed whale (Peponocephala electra), Fraser’s dolphin (Lagenodelphis hosei), spinner dolphin (Stenella longirostris), Risso’s dolphin (Grampus griseus), Indo-pacific bottlenose dolphin (Tursiops aduncus), dwarf sperm whale (Kogia sima), short-finned pilot whale (Globicephala macrorhynchus), and Pantropical spotted dolphin (Stenella attenuata). Mixed-species encounters were observed to be most frequent between the melon-headed whale and Fraser’s dolphin (i.e. 66% of the time) followed by Fraser’s and Risso’s dolphin mixed-groups.
Acebes J.M.V., Silberg J.N., Gardner T.J., Sabater E.R., Tiongson A.J.C., Dumandan, P., Verdote D.M.M., Emata C.L., Utzurrum J., & Yaptinchay A.A. 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.
Acebes, J.M.V. 2014. A History of Whaling in the Philippines: A Glimpse of the Past and Current Distribution of Whales. In: J. Christensen and M. Tull
(Eds), Unsettled Seas: Historical Perspectives of Fisheries Exploitation in the Indo-Pacific. MARE Publication series, Vol. 12.
Acebes, J.M.V. 2013. Hunting “Big Fish”: a marine environmental history of a contested fishery in the Bohol Sea. Unpublished PhD dissertation. Asia Research Center, Murdoch University, Perth, WA, Australia.
Acebes, J.M.V. 2009. Historical whaling in the Philippines: origins of ‘indigenous subsistence whaling’, mapping whaling grounds and comparison with current known distribution: a HMAP Asia Project Paper. Working Paper No. 161. Asia Research Centre at Murdoch University. Available at [http://wwwarc.murdoch.edu.au/publications/wp/wp161.pdf]
Clarke, D., Ponzo, A., Silberg, J.N., Senigaglia, V., Hughes, K., Birdsall,C. 2013. Site fidelity of Risso’s dolphins (Grampus griseus) in the Northern Bohol Sea, Philippines. 2013. ‘A potentially small and resident population.’ Presented at the 20th Biennial Conference of the Society of Marine Mammalogy, 9-13 December 2013. University of Otago, Dunedin, New Zealand.
Dolar, M.L.L., Leatherwood, S.J., Wood, C.J., Alava, M.N.R., Hill, C.L. and Aragones, L.V. 1994. ‘Directed fisheries for cetaceans in the Philippines.’ Rep. int. Whal. Commn 44:439-49.
Dolar, M.L.L., Perrin, W.F., Taylor, B.L., Kooyman, G.L. and Alava, M.N.R. 2006. ‘Abundance and distributional ecology of cetaceans in the central Philippines.’ J. Cetacean Res. Manage. 8(1): 93-111.
Dolar, M.L.L., Leatherwood, S.J., Wood, C.J., Alava, M.N.R., Hill, C.L. and Aragones, L.V. 1994. Directed fisheries for cetaceans in the Philippines.” Rep. int. Whal. Commn 44:439-49.
Pahang, K.A., Ponzo, A., Acebes, J.M., Silberg, J.N., Yaptinchay, A.A., Clarke. D. and Birdsall. C. 2013. ‘The Bohol Rescue Unit for Marine Wildlife, an example of successful networking in a developing country.’ Presented at the 20th Biennial Conference of the Society of Marine Mammalogy, 9-13 December 2013. University of Otago, Dunedin, New Zealand.
Leatherwood, S., Dolar, M.L.L., Wood, C.J., Aragones, L.V. and Hill, C.L. 1992. ‘Marine mammal species confirmed from Philippine waters.’ Silliman Journal 36(1):65-86. (Special Issue on Biodiversity).
Perrin, W. F., Dolar, M. L. L. and Ortega, E. 1996. ‘Osteological comparison of Bryde’s whales from the Philippines with specimens from other regions.’ SC/47/NP2: 1–14, 8 figs.
Ponzo, A., Senigaglia, V., Silberg, J.N., Clarke, D. 2013. ‘Peps’ peeps. Socioecology of Peponocephala electra in the Bohol Sea, Philippines.’ Presented at the 20th Biennial Conference of the Society of Marine Mammalogy, 9-13 December 2013. University of Otago, Dunedin, New Zealand.
Ponzo, A., Pahang, K.A., Silberg, J., Haskins, G., Emata, C.L.P., Acebes, J.M. 2011. ‘Presence and distribution of cetaceans in the north-eastern Bohol Sea.’ Presented at the 19th Biennial Conference of the Society of Marine Mammalogy, 26 November – 2 December 2011. Tampa, Florida, USA.
Sabater E.R. 2008. Relative abundance, distribution, and species association of cetaceans in the Bohol Marine Triangle, Philippines. MSc Thesis. Philippines: Silliman University.
Sabater, E.R. 2005. ‘Cetaceans of the Bohol Marine Triangle Area, Bohol, Philippines: Assessment and Monitoring.’ Presented at the 16th Biennial Conference of the Society of Marine Mammalogy, 12-16 December 2005, San Diego, C.A.
Sasaki, T., M. Nikaido, S. Wada, T. K. Yamada, Y. Cao, M. Hasegawa and N. Okada. 2006. Balaenoptera omurai is a newly discovered baleen whale that represents an ancient evolutionary lineage. Molecular Phylogenetics and Evolution 41:40–52.
Silberg, J., Ponzo, A., Pahang, K.A., Haskins, G., Emata, C.L.P. 2011. ’Site fidelity of melon-headed whales in the northern Bohol Sea, Philippines.’ Presented at the 19th Biennial Conference of the Society of Marine Mammalogy, 26 November – 2 December 2011. Tampa, Florida, USA.
Slijper, E.J., Van Utrecht, W.L. and Naaktgeboren, C. 1964. Remarks on the distribution and migration of whales, based on observation from Netherlands ships. Bijbragen Tot De Djerkunde XXXIV. 34:3-93.
Tan, J.M.L. 1995. A Field Guide to Whales and Dolphins in the Philippines. 1st ed. Bookmark, Metro Manila. 125pp.
Tiongson A.J.C., Sabater, E.R. 2013. ‘Patterns of mixed-species associations of small cetaceans in the northwest Bohol Sea.’ Presented at the 20th Biennial Conference of the Society of Marine Mammalogy, New Zealand, 9-13 December 2013. University of Otago, Dunedin, New Zealand.
Wada, S., M. Oishi & T. K. Yamada, 2003. A. newly discovered species of living baleen whale. Nature, 426: 278–281.
Yamada, T.K, Kakuda T., Tajima, Y. 2008. Middle sized balaenopterid whale specimens in the Philippines and Indonesia. Mem. Natl. Mus. Nat. Sci., Tokyo, (45): 75–83.