Comoros Island Chain and Adjacent Reef Banks IMMA

Size in Square Kilometres

65 900 km2

Qualifying Species and Criteria

Humpback whale – Megaptera novaeangliae

Criterion A; B (ii); C (i, iii)

Blue whale – Balaenoptera musculus

Criterion A; B (ii); C (iii)

Sperm whale – Physeter macrocephalus

Criterion A; B (ii)

Melon-headed whale – Peponocephala electra       

Criterion B (ii)

Short-finned pilot whale – Globicephala macrorhynchus

Criterion B (ii)

Spinner dolphin – Stenella longirostris

Criterion B (ii)

Indo-Pacific Bottlenose dolphin – Tursiops aduncus

Criterion B (i)

Indian Ocean humpback dolphin – Sousa plumbea

Criterion A; B (i)

Pantropical spotted dolphins – Stenella attenuata

Criterion B (ii)

False killer whale – Pseudorca crassidens    

Criterion B (ii)

Dugong – Dugong dugon      

Criterion A; B (i)

Marine Mammal Diversity 

Criterion D (ii)

Physeter macrocephalus, Megaptera novaeangliae, Balaenoptera musculus, Tursiops aduncus, Tursiops truncatus, Stenella longirostris, Stenella attenuata, Sousa plumbea, Peponocephala electra, Globicephala macrorhynchus, Pseudorca crassidens, Grampus griseus, Feresa attenuata, Lagenodelphis hosei, Orcinus orca, Indopacetus pacificus, Ziphius cavirostris, Mesoplodon densirostris, Kogia breviceps, Kogia sima, Dugong dugon, Stenella coeruleoalba, Steno bredanensis


The area of the Comoros (Grande Comore, Mohéli, Anjouan), Mayotte and other reef banks under French jurisdiction (Zélée/Geyser complex and the Glorieuses) includes submarine canyons and a large number of seamounts located between the main islands. Small resident populations of coastal dolphins occur, particularly Indo-Pacific bottlenose dolphins (Tursiops aduncus) and endangered Indian Ocean humpback dolphins (Sousa plumbea) around Mayotte. Throughout the archipelago, high densities of oceanic delphinids have been recorded, particularly spinner dolphins, pantropical spotted dolphins and melon-headed whales (Peponocephala electra). Other common species include dwarf sperm, Blainville’s beaked whales, sperm whales, short-finned pilot whales, and false killer whales. The density of migrating humpback whales is particularly high off the south coast of Moheli, in the coastal waters of Grande Comore and on the Geyser/Zélée complex. Finally, dugongs still occur in small numbers in the lagoon of Mayotte, in the Moheli Marine Park (south coast), but this population has declined greatly over the past four decades.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

This region is a critical habitat for several threatened marine mammal species (particularly the sperm whale, the Indian Ocean humpback dolphin and the dugong), and a migratory corridor for blue whales (Kiszka et al. 2007a, 2007b, 2010a, 2010b, Pusineri et al. 2013). Information on the movements and distribution of sperm whales in this region remain scarce, but multiple sightings between Mayotte and Anjouan suggest the presence of an aggregation (Van Canneyt et al. 2010). Dugongs still occur in the Comoros, especially in the Mohéli Marine Park, but in small numbers (WWF EAME 2004; Muir & Kiszka 2012). Dugongs occur in small numbers in the lagoon of Mayotte although this species has declined since the early 80’s due to hunting and as bycatch in several fisheries. Probably less than 10 individuals are present throughout the lagoon (Kiszka et al. 2007b, Pusineri et al. 2013). Blue whales (Balaenoptera musculus) have been recorded on several occasions all year round, particularly off Mayotte (Kiszka et al. 2007a, J. Kiszka, unpublished data).

Criterion B: Distribution and Abundance

Sub-criterion Bi: Small and Resident Populations 

Small resident populations of coastal dolphins occur, particularly the Indo-Pacific bottlenose dolphin (Tursiops aduncus) and the endangered Indian Ocean humpback dolphin (Sousa plumbea) around Mayotte (Kiszka et al., 2010b, 2012). Using photo-identification data, from 2004 to 2008, estimated annual abundances of bottlenose dolphins ranged from 47 ±18 to 98 ±50 individuals, suggesting low population size across its range around the island (estimated population home range is 978 km², Pusineri et al. 2014). Indian Ocean humpback dolphins only occur in the lagoon of Mayotte, and less than 5 individuals currently remain in the area (J. Kiszka unpublished data). Some evidence suggests that spinner dolphins occurring around some islands are resident, particularly around Mayotte (Viricel et al. 2016). However, more work is required to improve our knowledge on the residency and movements of this species. Finally the area supports a small, resident and isolated population of dugongs, dependent upon seagrass beds for foraging, particularly around Mayotte and in Mohéli (Muir and Kiszka 2012).

Sub-criterion Bii: Aggregations

Throughout the area, high densities of oceanic delphinids have been recorded, particularly the spinner dolphin (Stenella longirostris), the pantropical spotted dolphin (Stenella attenuata) and the melon-headed whale (Peponocephala electra) (Kiszka et al., 2010a, 2010b, Laran et al. 2017). Other common species include the sperm whale (Physeter macrocephalus), the short-finned pilot whale (Globicephala macrorhynchus) and the false killer whale (Pseudorca crassidens) (Kiszka et al. 2010a, 2010b). During aerial surveys conducted in 2009-2010 in the region, a relatively dense patch of sightings of sperm whales has been recorded between the islands of Anjouan and Mayotte (off-effort sighting data, Van Canneyt et al. 2010).

Criterion C: Key Life Cycle Activities

Sub-criterion Ci: Reproductive Areas

This region is a migratory destination for humpback whales (Megaptera novaeangliae) between July and October (austral winter), where the majority of encountered groups are mother-calf pairs (Kiszka et al. 2010a, Ersts et al. 2011). The high proportion of mother-calf pairs suggests that the surrounding waters of Mayotte constitute a nursing ground for this species in the region (Ersts et al. 2011), like around the other Comorian islands (Kiszka et al. 2010a) and Glorieuses (Globice, 2005). Density of humpback whales is particularly high off the south coast of Moheli, in the coastal waters of Grande Comore and on the Geyser/Zélée complex (Kiszka et al. 2010a, Ersts et al. 2011). Reef banks off north and north-eastern Mayotte (Iris, Zélée and Geyser banks) have been surveyed in 2002 and 2003, especially to evaluate the density and group composition of wintering humpback whales. The densities of humpback whales ranged from 0.027 to 0.618 whales/nm2 across three reef banks. Females with calves were the most frequently encountered group type. Encounter rates ranged from 0.98 to 2.36 groups per hour of search effort. Presumably all other species described as being present year-round also reproduce in the area.

Sub-criterion Ciii: Migration Routes

The region is a known breeding ground for humpback whales during the austral winter (see above), but also a potential migratory corridor for other baleen whales and male sperm whales. Sightings of blue whales in August 2016 and April 2007 (Kiszka et al. 2007) suggest that pygmy blue whales (B. m. brevicauda) and possibly Antarctic blue whales (B. m. intermedia) migrate through the Comoros archipelago.

Criterion D: Special Attributes

Sub-criterion Dii: Diversity

The diversity of species present in the area is sustained by a high variation of ocean, coastal, reef and lagoon habitats, with 22 species of cetaceans recorded and the dugong (Kiszka et al. 2010a, 2010b, Laran et al. 2017). These cetacean species include sperm whale (Physeter macrocephalus), humpback whale (Megaptera novaeangliae), blue whale (Balaenoptera musculus), indo-Pacific and common bottlenose dolphins (Tursiops aduncus, Tursiops truncates), spinner dolphin (Stenella longirostris), pantropical spotted dolphin (Stenella attenuata), Indian Ocean humpback dolphin (Sousa plumbea), melon-headed whale (Peponocephala electra), short-finned pilot whale (Globicephala macrorhynchus), false killer whale (Pseudorca crassidens), Risso’s dolphin (Grampus griseus), pygmy killer whale (Feresa attenuata), Fraser’s dolphin (Lagenodelphis hosei), killer whale (Orcinus orca), Longman’s beaked whale (Indopacetus pacificus), Cuvier’s beaked whale (Ziphius cavirostris), Blainville’s beaked whale (Mesoplodon densirostris), pygmy sperm whale (Kogia breviceps), dwarf sperm whale (Kogia sima), dugong (Dugong dugon), striped dolphin (Stenella coeruleoalba), and rough-toothed dolphin (Steno bredanensis).

Supporting Information

Gore, M.A., Kinai, M.S., Ahmad, E., Hussain, B., Ormond, R. F., Siddiqui, P.J.S., Waqas, U., and Culloch, R. 2012. ‘Occurrence of whales and dolphins in Pakistan with reference to fishers’ knowledge and impacts’. Journal of Cetacean Research and Management 12: 235–247.     

Iqbal, P., 2014. ‘Distribution and Diversity of Organisms Along Pakistan Coast’. PhD thesis. Karachi : University of Karachi.

Kiani, M.S. 2014. ‘Studies on Marine Cetaceans in Coastal Waters of Pakistan’. PhD thesis. Karachi : University of Karachi.

Kiani, M.S., and Waerebeek, K.V. 2015. ‘A review of the status of the Indian Ocean humpback dolphin (Sousa plumbea) in Pakistan’. In: T.A. Jefferson and B.E. Curry (eds.) Advances in Marine Biology, Vol. 72, pp. 201-228. Oxford: Academic Press.

Mahanty, M.M., Latha, G. and Thirunavukkarasu, A. 2015. ‘Analysis of humpback whale sounds in shallow waters of the Southeastern Arabian Sea: An indication of breeding habitat’. Journal of Biosciences 40: 407-417.

Marine Mammal Research and Conservation Network of India Database –

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

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

Moazzam, M. and Nawaz, R. 2017. ‘Arabian humpback and baleen whale sightings along the Pakistan coast: information generated through WWF Pakistan’s fishing crew observer programme’. International Whaling Commission. SC/67A/CMP/05: 1-14.

Moazzam, M., and Nawaz, R., 2018. ‘Using a crew-based observer programme as a platform of opportunity for understanding the distribution of whales in the Northern Arabian Sea. Results of the 2017 fishing season’. International Whaling Commission. Bled.

Moazam, M. and Nawaz, R. 2019 .The distribution of whales in the Northern Arabian Sea along the coast of Pakistan obtained through Crew-Based Observer Programme- Results of the 2018 fishing season SC/68A/CMP/07-International Whaling Commission. Nairobi.

Pomilla, C., Best, P.B. Findlay, K.P., Collins, T., Engel, M.H., Minton, G., Ersts, P.J., Barendse, J., Kotze, P.J.H., Razafindrakoto, Y. et al., 2006. ‘Population structure and sex-biased gene flow in humpback whales from Wintering Regions A, B, C, and X based on nuclear microsatellite variation. Report nr SC/A06/HW38.Population structure and sex-biased gene flow in humpback whales from Wintering Regions A, B, C, and X based on nuclear microsatellite variation’. 1-22.

Sutaria, D. 2018. ‘Update on Baleen whale records from India’. Submitted as a report to the IWC CMP Sub-Committee.

Sutaria D., Sule M., Jog K., Bopardikar I., Panicker D. 2017. ‘Baleen Whale Records from the Arabian Sea, India’. A Note Submitted to the IWC Sub-Committee. SC/67a/CMP/03.

Willson, A., Leslie, M., Baldwin, R., Cerchio, S., Childerhouse, S., Collins, T., Findlay, K., Genov, T., Godley, B. J., Al Harthi, S., Macdonald, D.W., Minton, A.G., Zerbini, A. And Witt, M.J. 2018. ‘Update on satellite telemetry studies and first unoccupied aerial vehicle assisted health assessment studies of Arabian Sea humpback whales off the coast of Oman’. Report presented to the Scientific Committee of the International Whaling Commission. Bled.

Yatsu, A., Katto, F., Kakizoe, F., Yamanaka K. and Mizuno, K. 1998. ‘Distribution and biology of Sthenoteuthis oualaniensis in the Indian Ocean-preliminary results from the research cruise of the R/V Shoyo-Maru in 1995’. In: T. Okutani, R.K. O’Dor and T. Kubodera (eds.). Recent Advances in Cephalopod Fisheries Biology. pp. 145-153.Tokyo: Tokai University Press.


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