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Dugong aerial survey Northern Great Barrier Reef, November 2000


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Dugong aerial survey Northern Great Barrier Reef, November 2000
Date Record Created
Date Record Modified
Date Coverage
2000-11-01 to 2000-11-30
Time Period
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Geospatial Location
  • Northern Great Barrier Reef, Queensland, Australia.
  1. Type: brief

    The waters of northern Australia are internationally recognised as the stronghold of the dugong (Dugong dugon) which is listed as vulnerable to extinction by the IUCN (2000). Significant populations persist in Australian waters, and dugongs are specifically cited as one of the World Heritage values of the Great Barrier Reef World Heritage Area. Much of the information used to manage dugong populations in this region has been provided by aerial surveys using standardised techniques. We report here on aerial surveys conducted in the following regions in November 2000 to assess the status of the dugong: (1) the Northern Great Barrier Reef Region between Hunter Point (11°15’S — south of Cape York) and Cape Bedford (15°30’S — near Cooktown); and, (2) the region between Cape Bedford and 17°25’S (near Innisfail). These data are derived from dugong aerial surveys following transects in November 2000. Points indicate the number of animals observed. The source map in the report is shown at 1:1,500,000.

  2. Type: full

    Northern Great Barrier Reef Region The estimated size of the dugong population for this region in 2000 was 9081 dugongs (± s.e. 917). Statistical comparison of this result with those from previous surveys indicates that overall dugong numbers in the region are stable at the scale of the region as a whole. The survey technique is designed to detect regional scale trends and cannot accurately detect changes at a local scale even if they are occurring. The dugongs were distributed differently from previous surveys. The surveys in 1985, 1990 and 1995 indicated that Princess Charlotte Bay supported between 37% and 56% of dugongs in the northern GBR region. The corresponding proportion for 2000 was 24.5%. At the same time, the area south of Cape Melville supported 59% of the dugongs in the region, a proportion about twice as high as the percentages of between 25% and 32% in 1985, 1990 and 1995. The results of the 2000 survey add to a growing body of evidence from aerial surveys and satellite tracking that dugongs undertake large-scale movements. The reasons for such large-scale movements are not generally known, but at least sometimes appear to be associated with disturbance to their seagrass habitat. In some instances, large-scale movements are associated with large-scale episodic disturbance to habitat caused by cyclones and floods. The distribution and abundance of dugongs has influenced the placement of highly protected areas within this region. Great Barrier Reef Marine Park (GBRMP) zoning protects dugongs in the coastal waters of Shelburne Bay, the Friendly Point region, Corbett Reef and much of the region between Cape Melville and Lookout Point from extractive activities, especially fishing impacts including incidental capture in commercial gill nets and habitat damage from trawling. Such protection has been enhanced by the rezoned Far Northern Section of the Great Barrier Reef Marine Park, which provides increased protection for dugong and their habitats in Temple Bay, the Cape Direction region, parts of Princess Charlotte Bay and Bathurst Bay. Nonetheless, dugongs and dugong habitats are not specifically protected in intertidal areas in the Northern Great Barrier Reef Region that are outside the Great Barrier Reef Marine Park. The planned introduction of zoning which complements that introduced as a result of the rezoning of the Far Northern Section of the Great Barrier Reef Marine Park and the review of fisheries’ management arrangements by the Queensland Government, will help ensure threats to dugong in this region are minimised. The potential biological removal method was used to estimate sustainable anthropogenic mortality from all causes for a range of estimates of dugong life history parameters based on empirical data from various wild populations using values of both 0.5 and 1 for the recovery factor. The justification for using a recovery factor of 1 was that the temporal series of aerial surveys suggests that population numbers are stable at a regional scale. We also used a recovery factor of 0.5 because the dugong is listed as a threatened species in Queensland and the default value is 0.5 for such stocks. The middle value for the maximum rate of increase R max (=0.03) suggests that the following total annual anthropogenic mortalities should be sustainable: • for the whole NGBR region: 63 dugongs (RF= 0.5); 125 dugongs (RF=1) for Blocks 1-4; • the region south to Cape Bedford based on the population’s distribution in 2000: 36 dugongs (RF= 0.5); 72 dugongs (RF=1) for Blocks 1-4; and • the region south to Cape Bedford based on the population distribution in 1995 (worst case scenario): 13 dugongs (RF= 0.5); 26 dugongs (RF=1). Given that the population estimates in this report are relative estimates, these estimates of sustainable anthropogenic mortality should be revised when absolute population estimates become available.

  3. Type: note

    Survey Methodology: The surveys were conducted in November 2000. The aerial survey method used was the strip transect technique detailed in Marsh and Sinclair (1989a; 1989b), which involved flying twin-engine Partenavia B aircraft fitted with a GPS at a speed of 100 knots, and a height of 137 m Above Sea Level. We did not use line transect methodology for two reasons: (1) we wished to retain the same methodology as had been used in the other surveys in the temporal series; (2) we had been advised to retain the strip transect methodology in a review of dugong survey methodology conducted by Professor Ken Pollock and other experts in 1997.

  4. Type: note

    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). Contact Helene Marsh for GIS data.

Related Publications
  1. Dugong distribution and abundance in the northern Great Barrier Reef Marine Park - November 2000
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  1. Managed by: Prof Helene Marsh , School of Earth & Environmental Sciences
  2. Aggregated by: Dr Ivan Lawler , School of Earth & Environmental Sciences
Primary Contact
Prof Helene Marsh,
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Fields of Research
  1. 050202 - Conservation and Biodiversity (050202) (050202)
  2. 050206 - Environmental Monitoring (050206) (050206)
Socio-Economic Objective
  1. 960903 - Coastal and Estuarine Water Management (960903) (960903)
  1. aerial surveys
  2. great barrier reef
  3. marine mammal
Research Activity
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Research Themes
Tropical Ecosystems, Conservation and Climate Change
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License - Other
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Access Rights/Conditions
Open Access . If the data is not available via the provided link, please contact an associated party (preferrably the Manager as specified) for access.
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Data Location
Online Locations
  1. Dugong aerial survey (dugong) Northern Great Barrier Reef, November 2000 Maps and (Data File, Public)
Stored At
Dr. Helene Marsh, School of Earth and Environmental Science, James Cook University, Townsville, Qld 4811, AUSTRALIA
Marsh, Helene.; Lawler, Ivan. (2011). Dugong aerial survey Northern Great Barrier Reef, November 2000. James Cook University. (dataset).