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Dugong aerial survey (dugongs) Hervey Bay, November 1992


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Dugong aerial survey (dugongs) Hervey Bay, November 1992
Date Record Created
Date Record Modified
Date Coverage
1992-11-01 to 1992-11-30
Time Period
(no information)
Geospatial Location
  • Hervey Bay, Southern Queensland, Australia.
  1. Type: brief

    Sightings for dugongs in Hervey Bay area during the dugong aerials surveys in November 1992.

  2. Type: full

    We conducted dedicated aerial surveys to determine the distribution and abundance of dugongs in Hervey Bay and the Great Sandy Strait in August 1988, November 1992 and December 1993. The methods followed those of Marsh and Sinclair (1989a, 1989b) and Marsh and Saalfeld (1989). Sightings were recorded in a strip 200 m wide on each side of the aircraft, from an altitude of 137 m. Two isolated, independent observers were used on each side of the aircraft so factors could be derived to correct for the dugongs visible, but missed by observers [based on a mark-recapture analysis of sightings (perception-bias correction factor: Marsh and Saalfeld 1989). Results were standardised to correct for dugongs not at the surface at the time the plane passed over (availability-bias correction factor; Marsh and Sinclair 1989b). The same parallel, east-west-oriented transects were flown on each survey, except that the number of transects in Block 1 (Great Sandy Strait) was doubled for 1992 and 1993. This increased the survey intensity in this block from 9.6% in 1988 to 17% and 16.4% in 1992 and 1993, respectively. Surveys were conducted only under good weather conditions (Beaufort sea state ≤ 3), and we avoided flying during periods of severe glare (early morning, late afternoon and midday). The 1992 and 1993 surveys of the Great Sandy Strait were timed to coincide with high tide over most of the area. As the transects were of variable length, the ratio method was used to estimate the density, population size and associated standard errors for each block. The standard errors were adjusted to incorporate the error associated with each correction factor, as outlined in Marsh and Sinclair (1989a). The significance of the differences between the dedicated dugong surveys of Hervey Bay conducted in 1988, 1992 and 1993 was tested by ANOVA both with and without the modal Beaufort sea state for each transect as the covariate. Blocks and times were treated as fixed factors and transect as a random factor nested within block. Input data for all analyses were corrected densities km-2, based on mean group sizes and the estimates of the correction factors for perception and availability bias, each line contributing one density per survey based on the combined corrected counts of both tandem observer teams. The densities were transformed [log10 (x+l)] for analysis, to equalise the error variances.

  3. Type: note

    Please contact Helene Marsh 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).

Related Publications
  1. Response of Dugongs to Large-scale Loss of Seagrass. Aerial Surveys. Hervey Bay.
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Technical metadata
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  1. Managed by: Dr Alana Grech , ARC Centre of Excellence for Coral Reef Studies (7351)
  2. Aggregated by: Prof Helene Marsh , School of Earth & Environmental Sciences (6630)
Primary Contact
Dr Alana Grech,
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Fields of Research
  1. 050206 - Environmental Monitoring (050206) (050206)
  2. 050202 - Conservation and Biodiversity (050202) (050202)
Socio-Economic Objective
  1. 960902 - Coastal and Estuarine Land Management (960902) (960902)
  1. marine biology
  2. ARC Centre of Excellence for Coral Reef Studies
  3. aerial survey
  4. dugong
  5. marine mammal
  6. Great Barrier Reef
  7. Hervey Bay
  8. distribution
  9. dugong dugon
  10. abundance
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 (dugongs) Hervey Bay, November 1992, maps and (Data File, Public)
Stored At
Dr Alana Grech, ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville QLD 4811, Australia, Tel: +61 7 47815222
Marsh, Helene.; Grech, Alana. (2012). Dugong aerial survey (dugongs) Hervey Bay, November 1992. James Cook University. (dataset).