The Indo-Pacific Humpback Dolphin of the Arabian Region: A Status Review

Abstract

Abstract Records of Indo-Pacific humpback dolphin sight-ings, strandings, and museum specimens in the Arabian region were compiled and used to review the distribution and status of this species. Nominal usage of Sousa chinensis (Osbeck, 1765) has been retained as a pragmatic measure, although the species present in the region resembles Sousa plumbea (Cuvier, 1828). Little is known about the ecology of this species in the region. Most available information on S. chinensis in the region originates from the Sultanate of Oman, where this species is among the most commonly recorded cetaceans; however, there is no absolute measure of abundance for anywhere in the region and the status of the species is unknown. 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 discrete popu-lations within the region. Beach-cast/dead indi-viduals represent nearly two-thirds of all records (n=303) of this species in Oman. Live sightings indicate unusually large group sizes (up to 100 individuals) in the Arabian Sea and Arabian Gulf. Occasional associations with Tursiops sp. and Delphinus capensis tropicalis were documented. Mating behavior and the presence of calves were recorded in the months of April and May, and calves were also reported in June, October, November, and December. Threats to humpback dolphins in the Arabian region include incidental capture in fishing nets, coastal and offshore devel-opment (e.g., land reclamation, dredging, port and harbor construction), pollution, boat traffic, oil and gas exploration (including seismic survey-ing), military exercises, and biotoxins associated with red tide events. Evidence for historic and current directed catches of S. chinensis is limited, but opportunistic hunting may occur. Intraspecific variation in cranial measurements of individuals from the Arabian Sea coast of Oman fall within relative values found in individuals from the Saudi Arabian Gulf coast. Cranial abnormalities were few. Recommendations are made for conserva-tion management-oriented research focusing on stock identity and status assessments, as well as for monitoring of fisheries by-catch, clearer defi-nition of other threats, continued specimen and sample collection, and training of local scientists.Key Words: Humpback dolphin, Sousa, Arabia, Persian Gulf, Middle East, Oman, distribution, abundancy conservation