Ecology, Status, Fisheries Interactions and Conservation of Coastal Indian Ocean Humpback Dolphins and Indo-Pacific Bottlenose Dolphins on the West Coast of Madagascar (SC/65b/SM21)
Salvatore Cerchio, Norbert Andrianarivelo, Boris Andrianantenaina, Victoria Cordi
This progress report to the International Whaling Commission (IWC) Standing Sub-committee on Small Cetaceans describes activities conducted during the first two years of our three-year project, covering the period from July 1, 2011 to June 30, 2013 and the three major components of this project: (1) Defining priority habitat and population status: research field surveys in the Northwest of Madagascar; (2) Assessing by-catch and hunting: interview surveys in the Northwest of Madagascar; and (3) Reducing hunting of coastal dolphins: community engagement in the Southwest of Madagascar. During Component 1, boat surveys were conducted in the Northwest including island groups of the Nosy Be region, Nosy Mitsio region (Ankarea MPA) and Nosy Iranja region (Ankivonjy MPA), and results from 2011 to 2013 are presented in context of data collected around Nosy Be since 2007. Species diversity varied among the regions with 6 species encountered around Nosy Be during 679 hours of surveys across six expeditions, 3 species encountered off Nosy Mitsio during 113 hours in two expeditions, and 9 species encountered around Nosy Iranja during 132 hours in one expedition. The coastal species Indian Ocean humpback dolphins (Sousa plumbea) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) were sighted with regularity in the shallow waters around Nosy Be and Nosy Iranja regions. Encounter rates for S. plumbea were highest in the Nosy Be region at 0.50 groups/hour search (gp/hr), and similar in the Nosy Iranja region at 0.44 gp/hr, while much lower in the Nosy Mitsio region at 0.05 gp/hr. Encounter rates for T. aduncus were generally lower at 0.10 gp/hr in the Nosy Be region, and 0.13 in the Nosy Iranja region. A second form of Tursiops, tentatively
identified as an inshore form of T. truncatus, was encountered with less frequency (0.02 gp/hr) in the Nosy Be region. The high diversity of species sighting in the Nosy Iranja region, within the Ankivonjy MPA, was likely due to the diversity of habitat and presence of deep water, and included encounters of blue whales (Balaenoptera musculus), beaked whales (Ziphiidae sp.), large groups (>500) of spinner and spotted dolphins (Stenella longirostris and S. attenuata). During Component 2, interview surveys were conducted with local fishers in the Nosy Mitsio and Nosy Iranja regions, to assess fisheries interactions and collect information about the occurrence, hunting and by-catch of all marine mammals, with a focus on collecting data on the prevalence of previously documented coastal dolphin hunting and by-catch. Interviews were conducted in 27 villages with a total of 147 fishers. No directed hunting on coastal dolphins was reported, however by-catch was found to be a threat particularly to Tursiops. Notably, dugongs were reported hunted and by-caught in both regions, though recently (during 2012) only in the Nosy Iranja / Ankivonjy region where an extant
population may still range. During Component 3, community engagement was done in the Southwest community of Befandefa, where extensive hunting on coastal dolphins had previously been reported during interview surveys in 2010. To address this threat, an intervention model previously developed in the Anakao region has been implemented to 1) create local conservation associations, 2) develop local traditional laws, or Dina, 3) educate and raise awareness and 4) develop alternative livelihoods. To date, 15 villages in four distinct communities have been engaged with positive response. Local conservation associations have been formed and organized, the process of developing local Dina has begun, and an awareness raising campaign has been instituted. These three components together represent different stages in a larger strategy of conservation of coastal cetaceans in a region of the Southwest Indian Ocean where hunting and by-catch are
pervasive threats to populations.