Southern Gulf of Carpentaria IMMA

Size in Square Kilometres

49,955 km2

Qualifying Species and Criteria

Dugong – Dugong dugon

Criterion A; C (i, ii)

Australian snubfin dolphin – Orcaella heinsohni

Criterion A

Marine Mammal Diversity 

Pseudorca crassidens, Sousa sahulensis, Stenella longirostris roseiventris, Tursiops aduncus

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The Gulf of Carpentaria is a large, remote, shallow embayment shared by the Northern Territory, Queensland and Commonwealth jurisdictions, bounded by Arnhem Land to the west and Cape York Peninsula to the east. Most of the Gulf has a meso-tidal range (2-4 m). The coastline generally has low wave energy enabling inshore seagrass and mangrove communities to establish, especially along the southern coast where there are offshore islands (Poiner et al. 1987, Roelofs et al. 2005, Taylor et al. 2007 ). The major rivers influence the local hydrodynamics and the mixing of fresh and marine waters plays an important role in the sedimentation of organic matter and locking of nutrients into the shallow coastal zone (Palmer and Smit 2019). The inshore waters are extremely turbid. This IMMA comprises the coastal waters from the northern boundary of Blue Mud Bay (13oS) to west coast of Cape York (around 141° longitude) to the 30 m depth contour and comprises the most important dugong habitats in the Northern Territory (Elliott et al. 1979, Marsh et al. 2008, Groom 2020). The Wellesley Islands in Queensland are also globally significant dugong habitat. The seagrass beds in parts of this region are intermittently destroyed by cyclones (e.g. see Kenyon and Poiner 1987) and dugongs have to move along the coast in search of food, which is why the IMMA includes the area between the Sir Edward Pellew Islands and the Wellesley Islands (Sheppard et al. 2006) and east of the Wellesley Islands, where seagrass has been recorded, especially  near Burketown and the mouth of the Normanby River, near Karumba (Coles et al. 2018). The region also supports globally significant populations of Australian snubfin dolphins.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

Both the dugong (Marsh and Sobtzick 2019) and the Australian Snubfin dolphin (Parra et al. 2017) occur in this IMMA and are listed by IUCN as Vulnerable. This IMMA supports the highest density of dugongs in the Northern Territory (Elliott et al. 1979, Marsh et al. 2008; Groom 2020). The most recent abundance estimates for the Northern Territory waters are 4600+/-se 1300 in 2019 (Pollock et al. method, Groom 2020), which is > 1% global population. Dugong numbers around the Wellesley Island group in Queensland area are also globally significant (relative abundance estimate 6000 +/-se1500 in 2007; >1% of global population using Pollock et al. method, Marsh 2008, Marsh et al. 2011).  Overall, the IMMA supports >3% of the estimated global dugong population.

Blue Mud Bay and Limmen Bight are consistent hotspots for snubfin dolphins (Freeland and Bayliss 1989, Groom et al. 2017). The highest densities along the Northern Territory coast were recorded at these locations with 0.34 and 0.21 snubfin/km2, respectively. The focal areas mentioned above for both dugongs and Australian snubfin dolphins have been consistent for more than 30 years suggesting that the populations are resident. One dugong was satellite tracked moving between the Sir Edward Pellew and the Wellesley Island areas (Sheppard et al. 2006); the 10 other dugongs satellite tracked in the Sir Edward Pellew region were resident there over the 8 month tracking period (Udywer et al. 2019).

Criterion C: Key Life Cycle Activities

Sub-criterion Ci: Reproductive Areas

The percentage of dugong groups with calves in the Northern Territory Waters of the Gulf of Carpentaria ranged from 13% to 20.6 % over the approximate 30-year period of the time series of aerial surveys but did not change significantly across years (Groom 2020). The Sir Edward Pellew Islands and southern Limmen Bight areas have been consistently important areas for dugong calves (Groom 2020).

Sub-criterion Cii: Feeding Areas

The dugong is a seagrass community specialist (Marsh et al. 2011, 2018). The IMMA contains vast shallow water seagrass meadows (Taylor et al., 2007). Dugongs have been recorded feeding in the area during aerial surveys and satellite tracking captures (Marsh 2008; Groom et al., 2017).

Supporting Information

Bayliss, P. and Freeland, W. J. 1989. ‘Seasonal distribution and abundance of dugongs in

the western Gulf of Carpentaria’. Australian Wildlife Research, 16:141-149.

Coles R.G., Rasheed M.A., Grech A. and McKenzie L.J. 2018. ‘Seagrass Meadows of Northeastern Australia’. In: Finlayson C., Milton G., Prentice R., Davidson N. (eds) The Wetland Book. Springer, Dordrecht.

Elliott, M., Marsh, H., Heinsohn, G. E. and Gardner B. R. 1979. ‘Dugongs in the Northern Territory of Australia’. Environmental Conservation, 6:277-277.

Freeland, W.J. and Bayliss, P. 1989. ‘The Irrawaddy River dolphin (Orcaella brevirostris) in coastal waters of the Northern Territory, Australia: distribution, abundance and seasonal changes’. Mammalia, 53(1):49-58.

Groom, R. 2020. ‘Re-thinking the assessment and monitoring of large-scale coastal developments for improved marine megafauna outcomes’. Professional Doctorate in Tropical Environmental Management thesis, James Cook University, Australia.

Groom, R., Dunshea, G.J. and Griffiths, A. D. 2015. ‘The distribution and abundance of dugong and other marine megafauna in the Gulf of Carpentaria, Northern Territory, November 2014’. Department of Land Resource Management, Flora and Fauna Division, Berrimah.

Groom, R. A., Dunshea, G. J., Griffiths, A. D. and Mackarous, K. 2017. ‘The distribution and abundance of dugong and other marine megafauna in Northern Territory’. Department of Environment and Natural Resources, Darwin. 

Kenyon, R., and Poiner, I. 1987. Seagrass and cyclones in the western Gulf of Carpentaria. CSIRO Marine Laboratories Information Sheet, 1 February 1987

Marsh, H. 2008. ‘Distribution and abundance of dugong in the Gulf of Carpentaria water: A basis for cross jurisdictional conservation planning and management. Australian Centre for Applied Marine Mammal Science’. Final Report.

Marsh H., Corkeron, P., Preen, A. R. Pantus, F. 2000. ‘Aerial survey of the marine wildlife in Gulf of Carpentaria waters adjacent to Queensland’. Report to the Department of Environment, Australia, October 1998, revised March 2000.

Marsh, H., and Sobtzick, S. (2019) Dugong dugon (amended version of 2015 assessment). The IUCN Red List of Threatened Species 2019: e.T6909A160756767. Available at: Accessed: 12 February 2020. 

Marsh, H., O’Shea, T.J. and Reynolds, J.E. III. 2011.  The ecology and conservation of Sirenia: dugongs and manatees. Cambridge University Press, Cambridge, UK.

Marsh, H., Grech, A. and McMahon K. 2018. ‘Dugongs: Seagrass Community Specialists’. In: A. Larkum A., G. Kendrick., P. Ralph. (eds) Seagrasses of Australia. Springer. Available at:  DOI (Accessed: 27 June 2020)

Palmer, C. and Smit, N. (2019). ‘Limmen Bight Marine Park: marine and coastal biodiversity values’. Department of Environment and Natural Resources, Northern Territory Government.

Palmer, C., Brooks, L., Fegan, M. and Griffiths, A. D. 2017. ‘Conservation status of coastal dolphins in the Northern Territory’. Final Report. Marine Ecosystems Group, Flora and Fauna Division, Department of Environment and Natural Resources. Darwin. Available at:

Parra, G., Cagnazzi, D. and Beasley, I. 2017. ‘Orcaella heinsohni’. The IUCN Red List of Threatened Species 2017: Available at: e.T136315A50385982. (Accessed: 6 March 2018). 

Poiner, I., Staples,D. and Kenyon, R. 1987. ‘Seagrass communities of the Gulf of Carpentaria, Australia’. Australian Journal of Marine and Freshwater Research, 38:121-131.

Pollock, K., Marsh H., Lawler I. and Alldredge, M.  2006.   ‘Modelling availability and perception processes for strip and line transects: an application to dugong aerial surveys’. Journal of Wildlife Management, 70:255-262.

Roelofs, A., R. Coles, R. and Smit, N. 2005. ‘A survey of intertidal seagrass from Van Diemen Gulf to Castlereagh Bay, Northern Territory, and from Gove to Horn Island, Queensland’.

Sheppard, J. K., Preen, A. R., Marsh, H., Lawler, I. R., Whiting, S. D. and Jones, R. E. 2006. ‘Movement heterogeneity of dugongs, Dugong dugon (Müller), over large spatial scales’. Journal of Experimental Marine Biology and Ecology, 334:64-83.

Taylor, H. A., Rasheed, M. A. and Coles, R. 2007. ‘Seagrass communities of the Wellesley Island Group’. Queensland Department of Primary Industries Publication PR07-3165.

Udyawer, V., Groom, R., Griffiths, A.D. and Thums, M. 2019. ‘Quantifying dive behaviour and three dimensional activity space of dugongs in the Gulf of Carpentaria’. Report prepared for the Department of Environment and Natural Resources. Australian Institute of Marine Science, Darwin.


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