These dolphins appear to have a very narrow habitat niche generally occurring within 2km of shore and in water less than 15m deep.
In Tanzania, Indian Ocean (IO) humpback dolphins are known to occur in some near-shore areas, but their presence is uncertain for several hundred kilometers of coastline, making informed conservation planning impossible. While their range is believed to extend from South Africa to India in the Western Indian Ocean, they appear to have a very narrow niche generally occurring within 2km of shore and in water less than 25m deep. Sousa plumbea is classified as Endangered by the IUCN Red List.
The IO humpback dolphins restricted, shallow-water habitat makes them very vulnerable to capture in fishing gear as well as hunting. Given that only small, isolated populations have been recorded in Tanzania, there is an urgent need to develop a conservation strategy based on sound research.
WCS completed a 'BigBlue Survey' in April 2015, covering approximately 2,600km of transects along the entire Tanzanian coast, including the islands of Mafia, Zanzibar and Pemba. IO humpback dolphins were only seen in very small numbers in the Rufiji Delta, and in shallow near-shore areas in the north of the country. They appear to be very rare or absent in the south. Research into the occurrence, habitat and threats to the IO humpback dolphin is needed to enable its conservation, so WCS collected data on the distribution and abundance of this species, as well as the characteristics of its habitat, and quantifying bycatch and hunting in the Greater Pemba Channel area.
Photo-identification using dorsal fin scars was used to understand the connectivity between areas of IO humpback dolphin concentration throughout East Africa. A bilateral ‘East African Cetacean Working Group’ was established to provide a mechanism for data sharing (photo id and genetic samples) between countries and research groups. This explored important questions about long-range movements of these dolphins across international boundaries and among isolated island populations. Understanding the impact of fisheries and other human activities on IO humpback dolphin populations are key to conservation planning.