A dugong monitoring network was established in the Rufiji Delta in 2004 which was the last known refuge in Tanzania for this critically endangered species. In 2009, a dugong was sighted on the west coast of Mafia Island and the network was extended to include Mafia. Members of the network, comprising Conservation Officers, local fishers and village leaders, record live dugong sightings and report dugong gill net mortalities.
Since the establishment of the dugong monitoring network, 67 dugong sightings have been reported to Sea Sense. Of these, 53 were live sightings (including two mother/calf pairs), 14 had drowned in gill nets (including one mother/calf pair) and one was stranded on a beach. Even though sightings are rare, there is clear evidence that a small breeding population exists in the Rufiji Delta - Mafia Island seascape. There has been a steady increase in the number of reports of dugong sightings since 2004 which can most likely be attributed to Sea Sense awareness and education programmes.
Tissue samples were taken from nine of the stranded dugongs and sent to James Cook University in Australia for analysis. DNA was successfully extracted from four of the samples and compared to DNA from dugongs in the Arabian Gulf. The results suggest that there is little genetic variation in east African dugongs, and that they are genetically close to dugongs from the Arabian Gulf.
In early 2014 a regional dugong research and conservation project was launched, funded by the Western Indian Ocean Marine Science Association (WIOMSA). The project is a regional collaboration between Tanzania, Kenya, Mozambique and Seychelles and Sea Sense is the lead investigator in mainland Tanzania. The project aims to re-evaluate the status of the east African dugong meta-population. All four countries are conducting the same surveys using standardized protocols to allow comparisons between sites and countries. The overarching product from this programme will be the formulation of a regional Dugong Conservation and Management Plan and a series of site specific plans across the range of dugongs on the east African mainland coast and across select oceanic island habitats.
Over the past year, Sea Sense has been conducting seagrass habitat surveys in the Rufiji Delta and on the west coast of Mafia Island, where recent dugong sightings have been reported. Survey teams identified seven seagrass species and recorded dugong feeding trails at Mbarakumi Island and Bwejuu in Mafia and in Mohoro Bay in the Rufiji Delta. Prior to the surveys, dugong sightings and mortalities had been reported within the Rufiji– Mafia Seascape but the exact location of their feeding habitat was unknown.
In the forthcoming months, Sea Sense will deploy acoustic receivers at dugong hotspots that were identified through the habitat surveys. The acoustic receivers contain a hydrophone end-cap which will record dugong vocalizations (barks, chirps and whistles). Since dugongs spend significant time in shallow, turbid waters and are often active at night, passive acoustic recording is a useful tool for remote detection of dugongs. Analyses of the vocalizations will provide information on the number of individuals utilising the area and improve understanding of the patterns of habitat use.
In 2006 and 2008 Sea Sense conducted aerial surveys to assess the distribution and abundance of dugongs in the Rufiji Delta. A mother and calf were observed in seagrass beds during one aerial survey but no other observations were made.
Sea Sense plans to repeat aerial surveys in 2016 as part of the WIOMSA funded project. 17 potential dugong hotspots have been identified within the region, seven of which have been prioritized for population assessments using aerial surveys, including Mafia Island.