Cetacean diversity and occurrence has never been investigated in the Union of the Comoros, located in the northern Mozambique Channel. Small boat-based surveys were conducted during the austral winter of 2002, primarily to assess the occurrence of humpback whales (Megaptera novaeangliae) and whether the area represents a wintering ground where the species reproduce. All other cetacean species were also recorded. Opportunistic sighting records were used to provide information on the diversity of cetaceans occurring in the area. Between 2000 and 2003, 12 cetacean species were recorded around the Comoros, including: Megaptera novaeangliae, Stenella longirostris, Peponocephala electra, Stenella attenuata, Tursiops truncatus, Globicephala macrorhynchus, Mesoplodon densirostris, Physeter macrocephalus, Lagenodelphis hosei, Grampus griseus, Mesoplodon pacificus and possibly Tursiops aduncus. During the dedicated surveys, the humpback whale was the most commonly encountered species (72% of sightings) followed by the spinner dolphin (15%). Humpback whale group composition was heterogeneous, but mother-calf pairs were the most commonly sighted (49%). This study demonstrates that the Union of the Comoros is an important site for migrating humpback whales in the southwest Indian Ocean and for a wide variety of toothed cetacean species.
©2010 by Walter de Gruyter Berlin New York