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Marine Ecology Progress Series

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MEPS 162:287-299 (1998)  -  doi:10.3354/meps162287

Winter distribution and possible migration routes of humpback whales Megaptera novaeangliae in the southwest Indian Ocean

P. B. Best1,*, K. P. Findlay1,**, K. Sekiguchi1,***, V. M. Peddemors2, B. Rakotonirina3, A. Rossouw1, D. Gove4

1Mammal Research Institute, Whale Unit (University of Pretoria), c/o S. A. Museum, PO Box 61, Cape Town, 8000 South Africa
2Natal Sharks Board, Private Bag 2, Umhlanga, Kwazulu-Natal, 4320 South Africa
3Institut Halieutique et des Sciences Marines, Université de Toliara, Madagascar
4Dept of Biological Sciences, University of Eduardo Mondlane, PO Box 257, Maputo, Mozambique
Present addresses:
**Oceanography Dept, University of Cape Town, Rondebosch, 7700 South Africa
***450 Ka'anini Circle, Hilo, Hawaii 96720, USA

The distribution and seasonality of humpback whales Megaptera novaeangliae in the southwest Indian Ocean are investigated from a number of sources. These include sighting and acoustic data collected on shore-based surveys on the African coast and from dedicated ship-based surveys in the coastal waters of Mozambique, Madagascar, across the Mozambique Channel and along the Madagascar Ridge, plus aerial sighting data from the Durban (South Africa) whaling ground, historical catch data by 10 d period for whaling operations at Durban, Linga Linga (Mozambique) and Madagascar, and incidental sightings data from a research ship and transiting merchant vessel. Three principal migratory routes are proposed. The first ('East African') strikes and leaves the African coast at least as far west as Knysna (23° E). The number and timing of peak abundances at Durban, Cape Vidal (South Africa) and Linga Linga suggest that this migration continues as far as central Mozambique, where abundance peaked in the first 10 d of August, and is slower and more protracted on the way south than on the way north. The second route ('Madagascar Ridge') supplies the coast of Madagascar directly from the south, probably via the Madagascar Ridge. The seasonality of catches in modern whaling in southern Madagascar implies that this migration proceeds somewhat further north, and one nineteenth-century whaling ground was on the northeastern coast of Madagascar at 15°30'S. The existence of the third migratory route ('Central Mozambique Channel') is based principally on the discovery of singing humpback whales in the centre of the Mozambique Channel in July/August and September, separate from contemporary singers on the continental shelves of Mozambique and Madagascar. The winter destination of this route may be the Comores Islands and Aldabra, where there have been a number of recent sightings.

Humpback whale · Migration · Indian Ocean

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