Northwest Madagascar and Northeast Mozambique Channel IMMA

Criterion A – Species or Population Vulnerability

Indian Ocean humpback dolphin, Sousa plumbea (IUCN Red List EN, Braulik et al. 2015, 2017). The conservation status of the Indian Ocean humpback dolphin is reported to be heterogeneous along the west coast of Madagascar; population(s) in the southwest are highly impacted (where active hunting occurs in the waters of the Vezo people), whereas population(s) in the northwest appear to be healthier and more abundant (Cerchio et al. 2009, 2014, 2015b; Razafindrakoto 2004). The regions encompassed by the IMMA, well documented around the Nosy Be, Nosy Iranja and Nosy Mistio area, appear to be a heaven for humpback dolphins relative to much of the other parts of their range in Madagascar. Antarctic blue whale, Balaenoptera musculus intermedia (IUCN Red List CR, Cooke 2018a). Passive acoustic monitoring from recording sites on the shelf break near Nosy Be indicated the presence of Antarctic blue whale song off northwest Madagascar throughout the Austral winter (Cerchio et al. 2018c). Some acoustic detections were high signal-to-noise ratio indicating presence within 10km of the shelf break, whereas it was suspected that most detections were within 100km of the coast. The offshore extent of the IMMA boundary was chosen to roughly encompass the likely range at which blue whales were detected acoustically during the austral winter, but it is likely that whales range further offshore into the Mozambique Channel (Cerchio et al. 2018c). SWIO pygmy blue whale, Balaenoptera musculus brevicauda (IUCN Red List EN, Cooke 2018b). Passive acoustic monitoring from recording sites on the shelf break near Nosy Be indicates the presence of SWIO pygmy blue whale song off the northwest Madagascar (Cerchio et al. 2018c). Some acoustic detection were high signal-to-noise ratio indicating presence within 10km of the shelf break, whereas it was suspected that most detections were within 100km of the coast. The offshore extent of the proposed IMMA boundary was chosen to roughly encompass the likely range at which blue whales were detected acoustically during the austral spring and fall migrations, but it is likely that whales range further offshore into the Mozambique Channel (Cerchio et al. 2018c). Sperm whale, Physeter macrocephalus, listed as Vulnerable (Taylor et al. 2008) has not been a focus of study in the waters of northwest Madagascar, however they use the deep offshore waters of the IMMA regularly and were encountered over the slope habitat during REMMOA aerial survey.  Visual surveys of deep waters in Nosy Be resulted in encounters near the 2000m depth contour, and acoustic monitoring produced numerous, but as yet unquantified, detections. Dugong, Dugong dugon, IUCN Red List VU (Marsh & Sobtzick 2015) is also encountered in the area (Cerchio et al. 2012b, Van Canneyt et al, 2010). The species is thought to have been historically widespread throughout Madagascar, but believed to be heavily exploited to the point that sightings of live animals are very rare. Population status is generally uncertain and it is possible/likely to have been extirpated throughout much of its former range (Cooke et al. 2003, Cerchio et al. 2012). Interview surveys with fishers along the west coast of Madagascar indicated decline in numbers of sightings and individuals captured in hunting and by-catch during the decade 2000-2010, and shifts in the relative distribution of reports over time, suggesting that populations in some locations may be more impacted or near extirpated (Cerchio et al. 2012).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations 

Omura’s whale, Balaenoptera omurai – Existing and recent data (including year-long acoustic monitoring, visual surveys, photographic identification, and satellite telemetry) indicate that this is a resident, non-migratory population whose distribution is likely determined by local shallow water ecological processes and patchy and ephemeral prey resources. Furthermore, this population of Omura’s whale may be isolated within a fragmented oceanic/global range for the species. The boundaries of the area encompass all of the range documented by boat surveys and satellite telemetry data including the offshore extent of documented movements, and likely most of the habitat for this population as indicated by habitat suitability modelling (Cerchio et al. 2015a, 2018a). Indian Ocean humpback dolphin, Sousa plumbea. The latitudinal range of the IMMA encompasses most if not all the coastal habitat for this species within that area where hunting pressure is believed to be least in Madagascar (Cerchio et al. 2009, 2014, 2015b; Razafindrakoto 2004). Dugong, Dugong dugon. There are interview accounts of relatively recent sightings, bycatch and hunting in the northwest Nosy Be region (Cerchio et al. 2012) and in the Diana region in the extreme northwest (C3-MIOIP 2010b), and aerial survey documentation of live sightings between Mahajanga and Bay of Sahamalaza in 2009 (Van Conneyt et al. 2010).  These data suggest that the northwest of Madagascar may constitute a range where a remnant viable population remains, but is still under hunting and bycatch pressure and likely in decline. During the REMMOA aerial survey (between mid December 2009 and early January 2010) relative density of dugong was estimated at 0.10 x 10-2 individuals.km² (CV: 74%), corresponding to probably less than 200 of dugongs in this area (Laran et al., 2012). The coastal boundaries of the area encompass all of these sites and the majority of the most recent sightings and documentation where a remnant viable population may remain in Madagascar (Cooke et al. 2003, C3-MIOIP 2010, Van Canneyt et al. 2010, Cerchio et al. 2012b).

Sub-criterion B2: Aggregations

Humpback whale, Megaptera novaeangliae – Humpback whales aggregate in the northwest of Madagascar during the late breeding season, as indicated by boat surveys and acoustic monitoring off Nosy Be (Cerchio et al. 2018c); Omura’s whale, Balaenoptera omurai –  Aggregations are regularly seen feeding on patches of krill, or producing a chorus of song display, in the Nosy Be region, with specific locales within surveyed habitat being clearly preferred on a micro-habitat scale (Cerchio et al. 2018 a,b). Melon-headed whales, Peponocephala electra – Large groups were encountered during REMMOA aerial survey resulting in the highest density of small blackfish of the blocks surveyed in the South West Indian Ocean (Laran et al., 2017), distributed mostly around Comoros Archipelago (out of this IMMA), but inside this IMMA also, along the Malagasy coast.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Humpback whale, Megaptera novaeangliae – Madagascar is a well-documented breeding area for humpback whales, and small boat surveys indicate that they are common in coastal waters of the Nosy Be region during the mid to late breeding season; year-long acoustic monitoring in the deep offshore waters of the Nosy Be region indicates near continuous presence of humpback whale song from at early July to mid-November (Cerchio et al. 2018c, Cerchio unpublished data). Antarctic blue whale, Balaenoptera musculus intermedia – Year-long acoustic monitoring in the deep offshore waters off the Nosy Be region indicated the presence of Antarctic blue whale song off northwest Madagascar throughout the Austral winter from June to September, suggesting previously unrecognized breeding season habitat (Cerchio et al. 2018c). Fin whale, Balaenoptera physalus – Year-long acoustic monitoring in the deep offshore waters off the Nosy Be region indicates presence of fin whales during the late Austral winter, from early August to mid-September (Cerchio et al 2018c). The timing of fin whale song suggests a later arrival than Antarctic blue whales and a lower rate of occurrence and occupancy, suggesting the northern extent of breeding habitat.

Sub-criterion C3: Migration Routes

Pygmy blue whale, Balaenoptera musculus brevicauda – Year-long acoustic monitoring in the deep offshore waters of the Nosy Be region indicates presence of the Madagascar-type pygmy blue whale song with bi-modal peaks of singing activity during May-July and October-January (Cerchio et al 2018c). This pattern suggests a previously unrecognized migratory corridor between summer feeding and winter breeding grounds south and north of Madagascar, respectively. This migratory corridor likely connects feeding habitat on the Madagascar Plateau and Ridge (Best et al. 2003) and likely breeding habitat off Kenya and the Seychelles area (Branch et al. 2007, Barber et al. 2016). Humpback whale, Megaptera novaeangliae – Satellite telemetry data indicates that this area of coast is a late season migratory corridor for humpback whales (Fossette et al 2014, Dulau et al 2017).

Criterion D: Special Attributes

Sub-criterion D2: Diversity

A minimum of 21 species of cetaceans and the dugong have been documented in the Nosy Be region (Van Canneyt et al. 2010, Cerchio et al. 2014, Cerchio et al. 2018c).  In addition to the species described above for other criteria, the following species are included for this criterion. Dwarf minke whale song vocalizations were detected on several days during non-systematic review of acoustic data from continental shelf waters around Nosy Be; it is possible that future analyses will indicate regular presence during the Austral winter, and thus breeding habitat (Cerchio et al. 2018b). Spinner dolphin is the most often sighted species by number of individuals in the continental slope and offshore areas (Cerchio et al. 2014a). Pantropical spotted dolphin is frequently sighted in the offshore areas during surveys around Nosy Be, at times in groups exceeding 500 individuals, and in combination with spinner dolphins, as well as on the continental shelf in smaller-sized groups (Cerchio et al. 2014a, unpublished data). Fraser’s dolphin were occasionally encountered in deep waters around Nosy Be, as were short-finned pilot whale with groups of up to more than 40 individuals, and Cuvier’s beaked whale (Cerchio et al. 2014a, unpublished data). Melon-headed whale and false killer whale were also occasionally encountered in shelf waters by tourists (Cerchio, unpublished data). During REMMOA aerial survey bottlenose dolphins, undistinguishable from common or Indo-Pacific, have a relative density of 7 x 10^-2 individuals.km² (CV: 30%) over the shelf area of Comoros and Malagasy coast (Laran et al., 2012) while Stenella spp. dominate the community with a density peaking to more than 30 x 10^-2 individuals.km² (CV: 59%) over the slope strata (Laran et al, 2012). Nevertheless, most of the large Delphinidae (Tursiops spp.) were encountered along Malagasy coast while Stenella spp. concentrated around Comoros archipelago. Melon-headed whales, encountered in large groups resulting in a density of 50 x 10^-2 individuals.km² (CV: 42%) for small blackfish (Globicephalinae) over the slope of this area and around the Comoros islands. The slope area has also sperm whale, beaked whales, with Cuvier’s and Longman’s beaked whale, false killer whale, short-finned pilot whale and Kogia sp. (Van Canneyt, et al. 2010, Cerchio et al. 2014a, unpublished data).