South West Madagascar and Mozambique Channel IMMA

Size in Square Kilometres

139 494 km2

Qualifying Species and Criteria

Sperm whale – Physeter macrocephalus

Criterion A

Antarctic Blue whale – Balaenoptera musculus intermedia

Criterion A; C (iii)

Pygmy Blue whale – Balaenoptera musculus brevicauda

Criterion A; C (iii)

Antarctic minke whale  – Balaenoptera bonaerensis

Criterion C (iii)

Fin whale – Balaenoptera physalus

Criterion A; C (iii)

Indian Ocean humpback dolphin – Sousa plumbea

Criterion A

Marine Mammal Diversity 

Criterion D (ii)

Balaenoptera bonaerensis, Balaenoptera musculus brevicauda, Balaenoptera musculus intermedia, Balaenoptera physalus, Globicephala macrorhynchus, Grampus griseus, Kogia breviceps, Kogia sima, Megaptera novaeangliae, Mesoplodon densirostris, Peponocephala electra, Physeter macrocephalus, Pseudorca crassidens, Sousa plumbea, Stenella attenuata, Stenella longirostris, Tursiops aduncus, Tursiops truncatus, Ziphius cavirostris

 

Summary

Located in the southern Mozambique Channel, along the southwest coast of Madagascar, this area encompasses diverse habitats, including peri-insular slope around Europa and Bassas da India atolls in the west of the area. A high diversity of cetaceans is encountered with more than 18 species. During large-scale aerial survey, REMMOA, most abundant species were large Delphinidae (Tursiops spp.) and small Globicephalidae (mostly melon-headed whale). Large Globicephalinae (mostly false killer whale and fewer short-finned pilot whale) were also abundant in the area, as were Risso’s dolphins. A relatively high density of beaked whales was estimated for the area, with a significant occurrence of small Delphininae (Stenella spp.), sperm whale and Kogia spp. In near coastal waters, there are impacted populations of Indian Ocean humpback and Indo-Pacific bottlenose dolphin. Passive acoustic monitoring indicates that pelagic waters represent a migratory route for Antarctic blue, pygmy blue, fin, Antarctic minke and humpback whales.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

Antarctic blue whales (Balaenoptera musculus intermedia) classified as Critically Endangered, and pygmy blue whales (B. m. brevicauda) classified as Endangered are both known to occur in the area during the austral summer (Anderson et al, 2012, Cerchio et al. 2018, Cerchio unpublished data). The Vulnerable sperm whale (Physeter macrocephalus) is located in deep-water habitats, whilst the Endangered Indian Ocean humpback dolphin (Sousa plumbea) is encountered in coastal areas, and to mitigate further decline of this species, conservation measures were recommended against direct hunting reported in the area (Cerchio et al. 2015)

Criterion C: Key Life Cycle Activities

Sub-criterion Ciii: Migration Routes

Antarctic blue whales (Balaenoptera musculus intermedia) occur in the tropical and subtropical Indian Ocean, and were estimated to 2,300 individuals (1,150 – 4,500) in the Southern Hemisphere IWC (2007). Based upon the presence of Antarctic blue whale song off the northwest coast of Madagascar during the austral winter (Cerchio et al. 2018), it is certain that the species migrate through this area. In the SWIO, a population of pygmy blue whales (Balaenoptera musculus brevicauda) is defined by the “Madagascar” song-type, heard from the Madagascar Ridge to the central Indian Ocean (McDonald et al. 2006, Samaran et al 2013). There is a likely summer feeding region on the Madagascar Ridge, for which abundance was estimated at 424-474 (Best et al. 2003). Based upon the bimodal presence of SWIO pygmy blue whale song off the northwest coast of Madagascar during the austral spring and autumn (Cerchio et al. 2018), it is certain that the species migrates through this area. Recent passive acoustic monitoring from the southwest coast of Madagascar (Toliara) has confirmed the presence of Antarctic blue whale song during at least the austral autumn, and SWIO pygmy blue whale song during at least the austral summer and autumn seasons (Cerchio, unpublished data). Given the potential for blue whale song to propagate long distances (in excess of 100km) it is likely that these animals were moving through the offshore extent of the IMMA.  In addition to the two blue whale subspecies, fin whales (Balaenoptera physalus), and Antarctic minke whales (B. bonaerensis) were also detected during the austral spring/summer (Cerchio, unpublished data) likely on migration through this area, as they have also been acoustically detected off northwest Madagascar during the austral winter (Cerchio et al. 2018).

Criterion D: Special Attributes

Sub-criterion Dii: Diversity

More than 18 species have been documented in this area through aerial surveys (Van Canneyt et al, 2010) and acoustic monitoring (Cerchio et al. 2018, Cerchio unpublished data). Most abundant species were large Delphininae (mostly common and some Indo-Pacific bottlenose dolphins) and small Globicephalinae (mostly melon headed whale, Laran et al, 2017). The taxonomic richness for this candidate area predicted from occupancy analyse of marine mammals (see Laran et al., 2017) is among maximum values obtained for the region. During REMMOA aerial surveys, the most abundant species were large Delphininae, mostly common and some Indo-Pacific bottlenose dolphins (Tursiops spp.) with a relative density of 17 x 10-2 individuals.km² (CV = 28%) in the area and small Globicephalidae (mostly melon headed whale, Peponocephala electra) with 6.3 x 10-2 individuals.km² (CV: 72%). Large Globicephalidae, mostly false killer whale (Pseudorca crassidens) and some short-finned pilot whale (Globicephala macrorhynchus) had a relative density of 3 x 10-2 individuals.km² (CV: 41%) and Risso’s dolphin with 3 x 10-2 individuals.km² (CV:41%). For deep divers, the highest density in this area were obtained for beaked whales (Cuvier’s’ beaked whale, Ziphius cavirostris and Blainville’s beaked whale, Mesoplodon densirostris) with 0,6 x 10-2 individuals.km² (CV: 56%), while sperm whale and Kogia spp. were estimated each with one order of magnitude less (without correcting for the availability bias due to dive duration of this species). Small Delphininae (Stenella spp.) were also significant in the area with relative density of 2,6 x 10-2 individuals.km² (CV = 41%, Laran et al, 2017). In the coastal waters the Indian Ocean humpback dolphin (Sousa plumbea) is encountered with direct hunting reported in the area (Cerchio et al, 2015). Other species as stripped dolphin (Stenella coeruleoalba), pygmy killer whale (Feresa attenuata) and killer whale (Orcinus orca) were encountered occasionally.

Supporting Information

Anderson, C., Branch, T.A., Alagiyawadu, A., Baldwin, R. and Marsac F. 2012. Seasonal distribution, movements and taxonomic status of blue whales (Balaenoptera musculus) in the northern Indian Ocean. Journal of Cetacean Resources and Management, 12 (2): 203-218.

Best, P.B., Rademeyer, R.A., Burton, C., Ljungblad, D., Sekiguchi, K., Shimada, H., Thiele, D., Reeb, D., Butterworth, D.S. 2003. The abundance of blue whales on the Madagascar Plateau, December 1996. Journal of Cetacean Research and Management, 5: 253–260.

Cerchio, S., Andrianarivelo, N., Andrianantenaina, B. 2015. Ecology and conservation status of Indian Ocean humpback dolphins (Sousa plumbea) in Madagascar. Advance in Marine Biology, 72: 163-199.

Cerchio, S., Trudelle, L., Zerbini, A.N., Charrassin, J.B., Geyer, Y., Mayer, F-X., Andrianarivelo, N., Jung, J-L., Adam, O., Rosenbaum, H.C. 2016. Satellite telemetry of humpback whales off Madagascar reveals long range movements of individuals in the Southwest Indian Ocean during the breeding season. Marine Ecology Progress Series, 562: 193-209.

Cerchio, S., Rasoloarijao, T., Cholewiak, D. 2018. Acoustic monitoring of Blue Whales (Balaenoptera musculus) and other baleen whales in the Mozambique Channel off the Northwest Coast of Madagascar. Paper SC/67B/SH/14 presented to IWC Scientific Committee.

Fossette, S., Heide-Jørgensen, M-P., Jensen, M.V., Kiszka, J., Bérubé, M., Bertrand, N., Vely, M. 2014. Humpback whale (Megaptera novaeangliae) post breeding dispersal and southward migration in the western Indian Ocean. Journal of Experimental Marine Biology and Ecology, 450: 6-14.

IWC. 2007. Annual Report of the Report of the International Whaling Commission.

Kiszka, J., 2015.  ‘Marine Mammals: A review of status, distribution and interaction with fisheries in the Southwest Indian Ocean’. In: R.P. Van der Elst and B.I .Everett (eds.)  Offshore fisheries of the Southwest Indian Ocean: their status and the impact on vulnerable species, pp. 305-322. Oceanographic Research Institute, Special Publication, 10.

Laran, S., Authier, M., Van Canneyt, O., Doremus, G., Watremez P. and Ridoux, V. 2017. A Comprehensive Survey of Pelagic Megafauna: Their Distribution, Densities, and Taxonomic Richness in the Tropical Southwest Indian Ocean. Frontiers in Marine Science, 4(139).

Mannocci, L., Laran, S., Monestiez, P., Dorémus, G., Van Canneyt, O., Watremez, P., Ridoux, V. 2013. Predicting top predator habitats in the South West Indian Ocean. Ecography 36: 1-18.

McDonald, M.A., Hildebrand, J.A., Mesnick, S,L. 2006. Biogeographic characterization of blue whale song worldwide: using song to identify populations. Journal of Cetacean Research and Management,8: 55–65.

Samaran, F., Stafford, K. M., Branch, R. A., Gedamke, J., Royer, J.-Y., Dziak, R. P., and Guinet, D. 2013. Seasonal and geographic variation of southern blue whale subspecies in the Indian Ocean, PLoS One 8(8), e71561.

Trudelle, L, Cerchio, S, Zerbini, AN, Geyer, Y, Mayer, F-X, Jung, J-L, Hervé, MR, Pous, S, Sallée, J-B, Rosenbaum, HC, Adam, O, Charrassin, J-B. 2016. Influence of environmental parameters on movements and habitat utilization of humpback whales (Megaptera novaeangliae) in the Madagascar breeding ground. R Soc Open Sci.;3:160616. doi: 10.1098/rsos.160616.

Van Canneyt, O., Dorémus, G., Laran, S., Ridoux, V., Watremez, P., 2010. REMMOA Sud Ouest Océan Indien: Rapport intermédiaire pour l’Agence des Aires Marines Protégées, 70 pp.

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