Gulf of Masirah and Offshore Waters IMMA

Size in Square Kilometres

23 881 km2

Qualifying Species and Criteria

Humpback whale – Megaptera novaeangliae

Criterion A; C (2)

Indian Ocean humpback dolphin – Sousa plumbea

Criterion A;

Marine Mammal Diversity 

Criterion D (2)

Balaenoptera edeni, Delphinus delphis tropicalis, Megaptera novaeangliae, Orcinus orca, Physeter macrocephalus, Pseudorca crassidens, Sousa plumbea, Stenella longirostris, Tursiops aduncus, Tursiops truncatus, Ziphius cavirostris


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Strong upwelling associated with the Southwest Monsoon supports high primary productivity in the Gulf of Masirah region. The area is among the most important habitats for Endangered Arabian Sea humpback whales (Megaptera novaeangliae). Sightings, acoustic records, telemetry data and whaling records confirm its importance for both feeding and breeding. The Endangered Indian Ocean humpback dolphin (Sousa plumbea) occurs along many coasts, with higher densities recorded in the large shallow bay of the Ghubbat Hashish in the northwest corner of the IMMA. Bryde’s whales (Balaenoptera edeni) have been observed with calves and feeding in the northern Gulf of Masirah, and feeding east of Masirah Island. Indo-Pacific bottlenose dolphins (Tursiops aduncus) were regularly observed in inshore waters during surveys in the early 2000’s, but sightings in recent years have been less frequent, which may be linked to bycatch and/or displacement. Pelagic species observed on the eastern side of the area include killer whales (Orcinus orca), false killer whales (Pseudorca crassidens), Cuvier’s beaked whales (Ziphius cavirostris) and sperm whales (Physeter macrocephalus). Recorded strandings and entanglements suggest several species are threatened with bycatch in gillnet fisheries.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The IUCN Red list currently classifies humpback whales globally as Least Concern. Arabian Sea humpback whales are listed by IUCN as ‘Endangered’ (Minton et al., 2008). Arabian Sea humpback whales are non-migratory, a trait unique among all humpback whale populations globally. They do not migrate between low-latitude breeding grounds and high latitude feeding grounds (e.g. Minton et al., 2011, Minton et al., 2008, Thomas et al., 2015, Reeves et al., 1991). The population is genetically distinct and reproductively isolated from other populations (Pomilla, Amaral et al., 2014). The Indian Ocean humpback dolphin (Sousa plumbea) is listed as ‘Endangered’ throughout its range by the IUCN Red List (Braulik et al., 2017). A total of 40 sightings of humpback dolphins were recorded within the IMMA during dedicated vessel surveys between 1986 and 2006 even though search effort was rarely directed towards finding humpback dolphins. Several authors have noted the regions importance for this species (e.g. Baldwin et al., 2004, Minton, 2004, Minton et al., 2010, Braulik et al., 2017). Recorded group sizes range between one to 100 individuals, including some of the largest groups sizes ever recorded (Baldwin et al., 2004 and Environment Society of Oman, 2018). Although no dedicated studies have been conducted in the area, the species is known to be a nearshore limited species with restricted home ranges (Braulik et al., 2017, Jefferson and Curry, 2015, Parra and Jefferson, 2018). As such, it can be inferred that all ecological requirements for the species are likely to be contained within the IMMA. Bryde’s whales (Balaenoptera edeni) as a species is designated as Least Concern in IUCN Red List (Cooke & Brownell 2018a). However this assessment does not make a distinction between any different forms of the species.  In the Arabian Sea and Sea of Oman, illegal Soviet whaling in the mid-1960s resulted in the recorded mortality of 849 individuals (Mikhalev 2000). There is little current information on the status of the Bryde’s whales in the region, and on whether both forms share the same status (Kershaw et al. 2013).  Evidence from relatively frequent strandings throughout much of the species’ NW Indian Ocean range suggests they are vulnerable to entanglement in gill nets and ship strikes as are other large whale species in the region (Baldwin, 2003; Baldwin et al., 2015).

Criterion C: Key Life Cycle Activities

Sub-criterion C2: Feeding Areas

The Gulf of Masirah is extremely productive, especially at the end of, and directly following the Southwest Monsoon season, as indicated by some of the highest remotely sensed Chrlophyll A values of any portion of Oman’s coastline (Banse and English, 2000; Brock and McClain, 1992; Piontkovski and Al Jufaili, 2013). This productivity is associated with a high fish biomass, supporting an expanding fisheries industry.  It is also associated with a relatively high rate of observed feeding or suspected feeding behaviour for both humpback whales and Bryde’s whales (Minton, 2004; Minton et al., 2011). Analysis of stomach contents from humpback whales taken from the Arabian Sea (n=190) showed that over 50% had ‘moderate’ to ‘plentiful’ stomach contents (Mikhalev, 1997; Mikhalev, 2000).  Catch locations curated by the International Whaling Commission indicate that at least 30 of these individuals were taken from the Gulf of Masirah (Allison 2016) and it is likely that they are represented in the sample of examined stomachs. Bryde’s whales are also thought to be feeding regularly in the area, supported by multiple observations during dedicated cetacean surveys of lunge feeding and/or whales in association with large shoals or sardines and other bait fish (Baldwin et al 1999; Ponnampalam, 2009; Minton, 2004; Environment Society of Oman, 2019).

Criterion D: Special Attributes

Sub-criterion D2: Diversity

The IMMA provides habitats for a minimum of 11 cetacean species that have been confirmed (Minton et al. 2010; Baldwin et al. 2011; Willson et al. 2015; ESO, 2018). Available habitats vary considerably, with humpback dolphins occupying nearshore waters (ranging from shallow bays to rocky headlands) and other species distributed exclusively offshore, including killer whales (Orcinus orca), false killer whales (Pseudorca crassidens), spinner dolphins (Stenella longirostris), Indo-Pacific common dolphins (Delphinus delphis tropicalis), sperm whales (Physeter macrocephalus) and Cuvier’s beaked whales (Ziphius cavirostris) have been recorded in deeper (>200m) offshore waters, particular to the east of Masirah Island. Data richness for the area is uneven, with the majority of observations recorded in the Gulf of Masirah and far fewer for offshore areas, including deep-water habitats and regions of very high productivity.

Supporting Information

Allison C. 2016. IWC individual catch database Version 6.1, Version 18 July, 2016

Baldwin, R. M. 2000. Oman’s humpback whales (Megaptera novaeangliae) The Journal of Oman Studies 11 11-18.

Baldwin, R., and R. V. Salm 1994. Whales and Dolphins along the Coast of Oman. Muscat Printing Press, Muscat.

Baldwin, R. M., T. Collins, K. Van Waerebeek, and G. Minton. 2004. The Indo-Pacific humpback dolphin of the Arabian region: A status review. Aquatic Mammals 30:111 – 124.

Baldwin, R. M. 2003. Whales and Dolphins of Arabia. Mazoon Printing Press, Muscat, Oman. 116pp.

Baldwin, R.M., Gallagher, M.D. and Van Waerebeek, K. 1999. A review of cetaceans from waters off the Arabian Peninsula. In: Oman’s Natural History, eds. Fisher, M., Spalton, A. and Gazanfar, S., Backhuys Publishers, Leiden. Pp. 161-189.

Baldwin, R. M., Willson, A and Collins, T. 2015. Watching out for whales: industry responsibility to address threats to Arabian Sea humpback whales in the Gulf of Masirah, Oman. Paper submitted to the International Whaling Commission Scientific Committee, IWC San Diego, 19 May – 1st June, 2015. SC/66a/SH23 (Available from IWC Office).

Banse K, English DC. 2000. Geographical differences in seasonality of CZCS-derived phytoplankton pigment in the Arabian Sea for 1978-1986. Deep-Sea Research Part II, 47: 1623-1677.

Braulik, G.T., Findlay, K.P., Cerchio, S., Baldwin, R.M. 2017. Assessment of the conservation status of the Indian Ocean Humpback dolphin Sousa plumbea using the IUCN Red List Criteria, in: Humpback Dolphins (Sousa spp.): Current Status and Conservation. Eds T.A. Jefferson, B.E. Curry, Advances in Marine Biology.

Brock JC, McClain CR. 1992. Interannual variability in phytoplankton blooms observed in the northwestern Arabian Sea during the southwest monsoon. Journal of Geophysical Research, 97: 733-750.

Brown, S.G. 1957. Whales observed in the Indian Ocean. Notes on their distribution. Mar. Obs. 27(177): 157–65.

Cerchio S, Willson A, Muirhead C, Minton G, Collins T, Baldwin R, Sarrouf Willson M, Al Harthi S. 2016. Preliminary report on long-term detection of Arabian Sea humpback whale vocalizations off Oman. Paper SC/66b/SH32 presented to IWC Scientific Committee.

Cooke, J.G. & Brownell Jr., R.L. 2018. Balaenoptera edeni. The IUCN Red List of Threatened Species 2018: e.T2476A50349178.

Corkeron, P., Minton, G., Collins, T., Findlay, K.,  Willson, A., and Baldwin, R . 2011. Spatial models of sparse data to inform cetacean conservation planning: an example from Oman. Endangered Species Research Vol. 15:39-52.

Environment Society of Oman. 2018. Oman Cetacean Database, (OMCD). OMCD Ver20160527-Update20170411. Accessed 2/11/2018.

Kershaw F., Leslie M.S., Collins T., Mansur R.M., Smith B.D., Minton G., Baldwin R., LeDuc R.G., Anderson R.C., Brownell R.L., Rosenbaum H.C. 2013. Population differentiation of 2 forms of Bryde’s whales in the Indian and Pacific Oceans. Journal of Heredity doi:10.1093/jhered/est057

Mendez, M., Subramanian, A., Collins, T., Minton, G., Baldwin, R., Berggren, P., Särnblad, A., Amir, O.A., Peddemors, V.M., Karczmarski, L., Guissamulo, A., Rosenbaum, H.C., 2011. Molecular ecology meets remote sensing: environmental drivers to population structure of humpback dolphins in the Western Indian Ocean. Heredity, 1-13.

Mikhalev, Y. A. 1996a. Bryde’s whales of the Arabian Sea and adjacent waters. Paper SC/49/O35 presented to the IWC Scientific Committee, June 1996. Pages 1-10.

Mikhalev, Y. A. 1996b. Pygmy blue whales of the Northern-Western Indian Ocean. Document presented to the 48th meeting of the International Whaling Commission SC/48/SH30. Pages 1-30.

Mikhalev, Y. A. 1997. Humpback whales Megaptera novaeangliae in the Arabian Sea. Marine Ecology Progress Series 149:13-21.

Mikhalev, Y. A. 1998. Sperm whales of the Arabian Sea. Paper SC/50/CAWS40 presented to the IWC Scientific Committee, April 1998. Pages 1-7.

Mikhalev, Y. A. 2000. Whaling in the Arabian Sea by the whaling fleets Slava and Sovetskaya Ukraina. In: Tormosov, D.D., Mikhalev, Y.A., Best, P.B., B., Zemsky, V.A., Sekiguchi, K., and Brownell Jr, R.L., editors. Soviet Whaling Data [1949-1979]. Moscow: Center for Russian Environmental Policy, Marine Mammal Council. p 141-181.

Minton, G. 2004. Ecology and conservation of cetaceans in Oman, with particular reference to humpback whales, Megaptera novaengliae (Borowski 1781). PhD Dissertation. University Marine Biological Station. University of London, Millport. 250pp.

Minton, G., Collins, T. J. Q., Pomilla, C., Findlay, K. P., Rosenbaum, H. C., Baldwin, R., and Brownell Jr, R. L. 2008. Megaptera novaeangliae, Arabian Sea subpopulation. IUCN Red List of Threatened Species

Minton, G., T. J. Q. Collins, K. P. Findlay & R. Baldwin. 2010. Cetacean distribution in the coastal waters of the Sultanate of Oman. Journal of Cetacean Research and Management, 11, 301-313.

Minton, G., T. J. Q. Collins, K. P. Findlay, P. J. Ersts, H. C. Rosenbaum, P. Berggren & R. M. Baldwin (2011) Seasonal distribution, abundance, habitat use and population identity of humpback whales in Oman. Journal of Cetacean Research and Management, Special Issue on Southern Hemisphere Humpback Whales, 185–198.

Papastavrou, V. and Van Waerebeek, K., 1997. A note on the occurrence of humpback whales (Megaptera novaeangliae) in tropical and subtropical areas: the upwelling link. Annu. Rep. Int. Whal. Comm, 47, pp.945-947.

Piontkovski SA, Al Jufaili S. 2013. Coastal upwellings and Mesoscale Eddies of the Western Arabian Sea: Some Biological Implications. International Journal of Oceans and Oceanography, 7: 93-115.

Pomilla, C. Amaral, A., Collins, T., Minton, G., Findlay, K., Leslie, M., Ponnampalam, L., Baldwin, R., Rosenbaum, H.  2014. The World’s Most Isolated and Distinct Whale Population? Humpback Whales of the Arabian Sea. PLoS ONE, 9(12), p.e114162. Available at:

Ponnampalam LS. 2009. Ecological studies and conservation of small cetaceans in the Sultanate of Oman, with special reference to spinner dolphins, Stenella longirostris (Gray, 1828).PhD, University of London.

Sheppard, C. ed., 2018. World Seas: An Environmental Evaluation: Volume II: The Indian Ocean to the Pacific. Academic Press.

Van Bressem, M.F., Minton, G., Collins, T., Willson, A., Baldwin, R and Van Waerebeek, K. 2014. Tattoo-like skin disease in the endangered subpopulation of the Humpback Whale, Megaptera novaeangliae, in Oman (Cetacea: Balaenopteridae). Zoology in the Middle East, 2014.

Willson, A., Baldwin, R., Minton, G. and Collins, T. 2012. Arabian Sea humpback whale research update for 2011/2012. Paper SC/64/SH30 presented to the International Whaling Commission Scientific Committee, Panama June 2012, (available from the IWC Office).

Willson, A., Baldwin, R., Minton, G., Gray, H., Findlay, K., Collins, T.  2013. Arabian Sea humpback whale research update for 2012/13. Paper SC/65a/SH06 presented to the International Whaling Commission Scientific Committee, Jeju, South Korea, June 2013. 08pp, (available from the IWC Office).

Willson, A., Baldwin, R., Cerchio, S., Geyer, Y., Godley B., Gray, H., Al-Harthi, S., Minton, Al-Zehlawi, N., M.Witt., Rosenbaum, H., Zerbini, A. 2014. Preliminary results and first insights from satellite tracking studies of male Arabian Sea humpback whales. Paper SC/65b/SH19 presented to the International Whaling Commission Scientific Committee, Slovenia, May 2014. (Available from the IWC Office).

Willson, A., Baldwin, R., Cerchio, S., Collins, T. Findlay, K., Gray, H., Godley B., Al-Harthi, S., Kennedy, A., Minton, G., Zerbini, A and Witt, M. 2015. Research update of satellite tracking studies of male Arabian Sea humpback whales; Oman. Paper SC/66a/SH22 presented to the International Whaling Commission Scientific Committee, San Diego, May 2015. (Available from the IWC Office).

Willson, A., Baldwin, R., Cerchio, S., Collins, T. Findlay, K., Gray, H., Godley B., Gray, H., Al-Harthi, S., Kennedy, A., Minton, Sucunza, F., Zerbini, A., Witt, M. 2016a. Research update on satellite tagging studies of the Arabian Sea humpback whale in the Sultanate of Oman. Paper SC/66b/SH28 presented to the International Whaling Commission Scientific Committee, Slovenia, June 2016. (Available from the IWC Office).

Willson, A., Kowalik, J., Godley, J., Baldwin, R., Struck, A., Struck, L., Nawaz, R. and Witt, M. 2016b. Priorities for addressing whale and ship strike co-occurrence off the coast of Oman and the wider North Indian Ocean. Paper SC/66b/HIM/10 presented to the International Whaling Commission Scientific Committee, Slovenia, June 2016. Available from the IWC Office).

Willson, A., Baldwin, R., Collins, T., Godley, B., Minton, G., Al Harthi, S., Pikesley, S., Witt. 2017. Preliminary ensemble ecological niche modelling of Arabian Sea humpback whale vessel sightings and satellite telemetry data. Paper presented to the International Whaling Commission Scientific Committee, Slovenia, May 2017. (Available from the IWC).


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