Aerial surveys for dugongs have been conducted over an area of some 39,000 km2 in the inshore waters of the Great Barrier Reef Marine Park (GBRMP) south of Cape Bedford in 1986/1987, 1992 and 1994. Survey specific correction factors have been used to correct for perception bias (the proportion of animals visible in the transect which are missed by observers) and to standardise for availability bias (the proportion of animals that are invisible due to water turbidity). These surveys indicate that the number of dugongs in the region has declined by approximately 50% over the past eight years from an estimated 3479 ± s.e. 459 in 1986/87 to 1682 ± s.e. 236 in 1994. Over a large section of the region, this decline is over 80%. This change does not appear to be due to emigration out of the region. It is most likely to be due to unsustainable dugong mortality within the region. Dugongs have a life-span of more than 70 years and bear only one calf at a time at intervals.

Please contact Helene Marsh Helene.Marsh@jcu.edu.au for GIS data. Funding for these surveys was obtained from the following government agencies: - Great Barrier Reef Marine Park Authority (GBRMPA), - Department of Environment and Resource Management (DERM), - Australian Marine Mammal Centre (AMMC), - Torres Strait Regional Authority (TSRA), - Australian Fisheries Management Authority (AFMA), - Marine and Tropical Sciences Research Facility (MTSRF), - National Environmental Research Program (NERP).