Aerial survey of dugongs and associated macrovertebrate fauna - Pilbara coastal and offshore regions.

This record is derived from DEC Marine Policy Branch Endnote library and spatially referenced SIER Database.

A report on the status of the dugong in the Torres Strait area was prepared for the Australian National Parks and Wildlife Service, based on the results of an aerial survey, presenting information on dugong life history and current catch levels: Marsh H, Barker-Hudson BET, Heinsohn GE and Kinbag F. (1984) Status of the dugong in the Torres Strait area: results of an aerial survey in the perspective of information on dugong life history and current catch levels. Report to the Australian National Parks and Wildlife Service, April 1984. James Cook University of North Qld, Townsville, Australia. 72pp.

This dataset shows a raster spatial model of the distribution and relative density of dugongs (Dugong dugong) in the northern Great Barrier Reef region based on an aggregate of 24 years (1990 - 2013) of systematic aerial surveys. Methods: Aerial surveys were conducted using the strip transect method described by Marsh and Sinclair (1989). The survey region was divided into blocks containing systematic transects of varying length, which were typically perpendicular to the coast across the depth gradient. Tandem teams with two observers on each side of the aircraft independently recorded sightings of dugongs, including information on group size and calf numbers. Transects were 200 m wide at the water’s surface on either side of the aircraft. The spatial data from all the aerial surveys in the region (1990, 1995, 2000, 2006, and 2013) were corrected for differences in sampling intensity and area sampled between surveys. For details on sampling intensities and areas, please refer to the reports and publications for each individual survey (list below). The corrected data were then interpolated using universal kriging over the spatial extent of the aerial surveys. Planning units were 2km * 2km and were classified as low (1), medium (2), high (3) and very high (4) dugong density on the basis of the relative density of dugongs estimated from the model and a frequency analysis. Low density areas: 0 dugongs per square km; medium density areas 0.0015 - 0.25 dugongs per square km; high density areas 0.25 - 0.5 dugongs per square km; very high density areas > 0.5 dugongs per square km. Limitations: The modelled abundance and distribution show the relative density of dugongs (areas where there are more or less animals) and NOT the absolute dugong density as corrections for perception bias (animals that are available to, but missed by, observers) and availability bias (animals that are unavailable to observers because of water turbidity) can only be applied at the spatial scale of entire surveys (thousands of square kilometres), making them inappropriate for the spatial scale for this dataset. Nonetheless, the relative densities among regions should be approximately comparable (H. Marsh, personal communication). Format: The spatial model is 2481x3509 pixels with a spatial reference of WGS84 UTM Zone 54S. The original dataset is stored in ESRI GRID format (60 KB), which was converted to a GeoTiff for use in the eAtlas (134 kB). Both datasets are available under a creative commons attribution license. References: Publications for aerial surveys in the northern Great Barrier Reef: Marsh, H. & Corkeron, P. (1996). The status of the dugong in the northern Great Barrier Reef. Report to Great Barrier Reef Marine Park Authority, Townsville. Marsh, H. & Lawler, I. R. (2002). Dugong distribution and abundance in the Northern Great Barrier Reef Marine Park: November 2000. GBRMPA Research Publication 77. Townsville, Australia: Great Barrier Reef Marine Park Authority. Marsh, H.D., Hodgson, A., Lawler, I., Grech, A., & Delean, S. (2007) Condition, status, and trends and projected futures of the dugong in the Northern Great Barrier Reef and Torres Strait; including identification and evaluation of the key threats and evaluation of available management options to improve its status. Marine and Tropical Sciences Research Facility Reports Series. Reef and Rainforest Research Centre Limited, Cairns (77pp.). Data Location: This dataset is filed in the eAtlas enduring data repository at: data\NERP-TE\1.2_GBR-Turtles-dugong-monitoing

Aerial survey of the distribution and abundance of dugongs and associated macroinvertebrate fauna- Pilbara Coastal and Offshore Region, W.A.

This dataset shows a spatial model of the distribution and relative density of dugongs (Dugong dugong) in the Torres Strait region based on an aggregate of 19 years (1986, 1987, 1992, 1994, 1999, and 2005) of systematic aerial surveys. For more information on the methods used in the creation of this dataset see Grech. A., and Marsh. H. (2007) - Prioritising areas for dugong conservation in a marine protected area using a spatially explicit population model, Applied GIS, 3(2), 1-14. All surveys were conducted in late spring or early summer when weather and sea states provide optimum survey conditions. This data presents the results of a model of dugong distribution and abundance, based on data collected from dugong aerial surveys, in conjunction with geostatistical techniques including universal kriging (Grech and Marsh 2007). After completing the model, frequency analyses were conducted to categorise relative dugong density and distribution to identify areas of low, medium or high conservation value. The modelled abundance and distribution show the relative density of dugongs (areas where there are more or less dugongs) and NOT the absolute dugong density as corrections for perception bias (animals that are available to, but missed by, observers) and availability bias (animals that are unavailable to observers because of water turbidity) can only be applied at the spatial scale of entire surveys (thousands of square kilometres), making them inappropriate for the spatial scale for this dataset. Nonetheless, the relative densities among regions should be approximately comparable (H. Marsh, personal communication). This dataset is being updated as part of Project 1.2 of the National Environmental Research Program. This dataset is an estimate of relative dugong density (number / km^2) and the conservation value with a 3-point rating (high, medium, low). Note: More recent surveys were completed under the NERP program.

To determine a minimum estimate of dugong population (relative dugong density) in Shark Bay, Ningaloo and Exmouth Gulf.

This record describes an AFMA/JCU funded project entitled 'Dugong distribution and abundance in Torres Strait'. This research was carried out by James Cook University. The project is described in the referenced report: Marsh H, Lawler IR, Kwan D, Delean S, Pollock K and Alldredge M. 2003. The status of the dugong in Torres Strait in November 2001. Project final report AFMA/JCU Final Report, Canberra, Australia.

Research article and relation data on the Australian dugong.

Fishery Assessment Report on Dugong in the Torres Strait 1999. Compiled by H. Marsh and edited by the Torres Strait Fisheries Assessment Group, for AFMA: Marsh, H. (1999) Torres Strait Dugong 1998, Fisheries Assessment Report, edited by the Torres Strait Fisheries Assessment Group. Australian Fisheries Management Authority, Canberra.