The Indian Ocean humpback dolphin <i>Sousa plumbea</i> (G.Cuvier, 1829). A status report for the Arabian region. Scientific Committee document SC/54/SM6, International Whaling Commission, 26 April-10 May 2002, Shimonoseki, Japan

Abstract

Available data on the genus Sousa are reviewed for the Arabian region. Nominal usage of Sousa plumbea (G. Cuvier 1828) is retained as a pragmatic measure, based on geographic and morphologic affiliation. Distribution is described for the region to include much of the Arabian (Persian) Gulf, Arabian Sea, Gulf of Aden and Red Sea, but notably excludes the Gulf of Oman. This discontinuous distribution suggests the possible presence of discreet populations within the region. Most available information on Sousa plumbea in the region originates from the Sultanate of Oman, where this species is among the most commonly recorded cetacean. However, there is no absolute measure of abundance here or elsewhere in the region and the status of the species is unknown. Beach cast individuals represent nearly two-thirds of all records (n=269) of this species in Oman. Live sightings indicate unusually large group sizes (up to 100 individuals) in the Arabian Sea and Arabian Gulf. Occasional association with Tursiops sp. and Delphinus sp. is documented. Mating behaviour and the presence of calves are recorded in the months of April and May and calves are additionally reported in October and December. Little is known about the ecology of this species in the region.Threats to Indian Ocean humpback dolphins in the Arabian region include incidental capture in fishing nets, general coastal and offshore development (e.g. land reclamation, dredging, port and harbor construction), pollution, boat traffic, oil and gas exploration (including seismic surveying), military exercises and toxins associated with red tide events. Evidence for historic and current directed catches of Sousa plumbea is presented.Intraspecific variation in cranial measurements is presented for cranially adult skulls originating from the Arabian Sea coast of Oman and initial comparison with limited data from the Saudi Arabian Gulf coast are drawn. Cranial abnormalities in skull specimens from Oman are discussed. Curated specimens from the Arabian region are listed