evaluation de la diversite des cetaces dans les eaux environnantes de nosy-be, nosy mitsio et nosy iranja, nord-ouest de madagascar

Abstract

As part of the project of establishment of Marine Protected area Ankarea and Ankivonjy in the
Northwest of Madagascar, a study of cetaceans was done at Nosy Mitsio, Nosy-Be and Nosy Iranja from 2011
to 2013. The research was conducted at the three sites for 98 days spread over three seasons with observation
769.99 hours efforts 8 077.80 km transect and identified 12 species of cetaceans: Balaenoptera musculus,
Balaenoptera omourai is a newly identified species in the Western Indian Ocean, Megaptera novaeangliae,
Physeter macrocephalus, Globicephala macrorhynchus, Lagenodelphis hosei, Sousa plumbea, Tursiops
aduncus, Tursiops truncatus, Ziphius cavirostris, Stenella longirostris and Stenella attenuata. 209 observations
of cetacean 8163 individuals were carried out with 62 baleen whale; Stenella represent the majority of small
cetaceans observed. We saw a large abundance of observation in Nosy Iranja with 0,324 group per hour, 0.279
group per hour on Nosy Be and only 0.085 group per hour Nosy Mitsio. Baleen whales have 0,051 groups per
hour and toothed whales 0,215 groups per hour. We also have done interview surveys of 45 villages in the three
sites Nosy Mitsio, Nosy Iranja and Ambaro Bay, 280 fishermen were interviewed and claimed 17 cetacean
species known in the interviewees’ areas, and they are sometimes known alive or by-caught or seen stranding.
No hunt was registered by fishermen in the study area, 35 cetaceans were incidentally caught with 03 humpback
whales, 01 right whale, 27 bottlenose dolphins and 04 Stenella and 57 individuals stranded within 02 right
whales, 21 humpback whales, sperm whales 06, one humpback dolphin, 03 Stenella and 24 bottlenose dolphins.