Houtman Abrolhos to Rottnest Shelf Waters IMMA

Size in Square Kilometres

19,297 km2

Qualifying Species and Criteria

Australian sea lion – Neophoca cinerea

Criterion A; C (i; ii)

Marine Mammal Diversity 

Balaenoptera musculus brevicauda, Megaptera novaeangliae, Tursiops aduncus


The Australian sea lion is endemic to Australia, it is the world’s rarest sea lion with the number of mature individuals in the population of around 6500 animals. It inhabits the offshore islands of the southwestern and southern coasts of Australia from the Houtman Abrolhos Islands in Western Australia to the Pages islands, South Australia. They are exceptional among pinnipeds by having an asynchronous breeding cycle making them difficult to monitor and manage. In addition, the metapopulation consists of small, genetically isolated subpopulations and was exploited by commercial sealing and has not successfully recovered. Although the breeding islands of the west coast of Western Australia account for only around 6% of total pup production, the high natal site fidelity of female Australian sea lions, the genetic isolation and that these islands are at the northernmost extent of the range, makes this subpopulation important. This IMMA covers the breeding colonies of Australian Sea Lions on islands on the west coast of Western Australia, including the Houtman Abrolhos Islands and the islands in and around Jurien Bay, and Beagle Island, Fisherman’s Island and Buller Island. It also includes a number of key haul-out sites along this coast. The Australian sea lion is Red Listed as Endangered (EN) (Goldsworthy 2015). This area is known for being important for breeding Australian sea lions, these islands and the surrounding area (out to around 24 km radius) are further important for sea lion foraging.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The Australian sea lion has been formally assessed and Red Listed by IUCN as Endangered (EN). The metapopulation was exploited by commercial sealing and has not successfully recovered (Gales et al. 1994, Goldsworthy 2015). The west coast population of Western Australia supports a small, genetically and geographically isolated population of approximately 700 to 800 (Gales et al., 1994) which accounts for ca 6% of pup production (Goldsworthy et al., 2009) and the Abrolhos Islands and other islands in the cIMMA are the northern most population of Australian sea lions. Being at the northern limit of the species range may make this sub-population unviable in the future due to reduced ocean productivity from warming oceans and potential increase in pup mortality on land due to heat stress and dehydration from a warming climate (Goldsworthy et al. 2009).

Criterion C: Key Life Cycle Activities

Sub-criterion Ci: Reproductive Areas

The IMMA is made up of 4 breeding colonies of the Australian sea lion and a number of key haul-out ‘non-breeding’ sites along this coast. The species mate, give birth, and care for young until weaning at these sites. Female Australian sea lions display an extremely high level of natal site fidelity, such that recruitment of females is almost exclusively from within each breeding colony (Campbell et al., 2008b, Lowther et al., 2012). This has important implications for the conservation management of this species, as virtually every breeding colony becomes a management unit (Campbell et al., 2008a).

Sub-criterion Cii: Feeding Areas

Australian sea lion satellite transmitter deployments, and the location of sea lion bycatch in rock lobster fishing gear show that sea lion foraging is predominantly located within 30 km of the breeding colonies/haul-out sites (Campbell et al., 2008a, Campbell, 2005). Adult males may range further; in the order of 100 km from their colony or haul out area (Goldsworthy et al., 2014) and spatial models predict foraging to occur within the continental shelf (within the 200 m contour). The tacking data and spatial modelling of the data underpins the Biologically Important Area for foraging Australian sea lions designated by the Australian Government (Australian Government Department of the Environment and Energy, 2016).

Supporting Information

Campbell, R. 2005. Report For The Sea Lion Scientific Reference Group. Interim Report For The Members Of The Western Rock Lobster Fishery/Sea Lion Interaction Scientific Reference Group (Slsrg).

Campbell, R. 2011. Assessing And Managing Interactions Of Protected And Listed Marine Species With Commercial Fisheries In Western Australia. Report To The Fisheries Research And Development Corporation. Fisheries Research Report No. 223. Department Of Fisheries, Western Australia.

Campbell, R., Holley, D., Christianopolous, D., Caputi, N. & Gales, N. G. 2008a. Mitigation Of Incidental Mortality Of Australian Sea Lions In The West Coast Rock Lobster Fishery. Endangered Species Research, 5, 345-358.

Campbell, R. A., Gales, N. J., Lento, G. M. & Baker, C. S. 2008b. Islands In The Sea: Extreme Female Natal Site Fidelity In The Australian Sea Lion, Neophoca Cinerea. Biology Letters, 4, 139-142.

Gales, N. J., Shaughnessy, P. D. & Dennis, T. E. 1994. Distribution, Abundance And Breeding Cycle Of The Australian Sea Lion Neophoca Cinerea (Mammalia: Pinnipedia). Journal Of Zoology, London, 234, 353-370.

Goldsworthy, S. D. 2015. Neophoca Cinerea. The Iucn Red List Of Threatened Species 2015:E.T14549a45228341. Http://Dx.Doi.Org/10.2305/Iucn.Uk.2015-2.Rlts.T14549a45228341.En.

Goldsworthy, S. D., Ahonen, H., Bailleul, F. & Lowther, A. D. 2014. Determining Spatial Distribution Of Foraging Effort By Australian Sea Lions In Southern Western Australia: Assisting In Spatial And Temporal Management Of Commercial Fisheries. Report To The Australian Marine Mammal Centre. South Australian Research And Development Institute (Aquatic Science), Adelaide. Sardi Publication No. F2014/000378-1. Sardi Research Report Series No. 784. 21pp.

Goldsworthy, S. D., Mckenzie, J., Shaughnessy, P. D., Mcintosh, R. R., Page, B. & Campbell, R. 2009. An Update Of The Report: Understanding The Impediments To The Growth Of Australian Sea Lion Populations. Sardi Research Report Series Number 356. South Australian Research And Development Institute (Aquatic Sciences), Adelaide.

Higgins, L. V. 1993. The Non-Annual, Non-Seasonal Breeding Cycle Of The Australian Sea Lion, Neophoca Cinerea. Journal Of Mammalogy, 74, 270-274.

Lowther, A. D., Harcourt, R. G., Goldsworthy, S. D. & Stow, A. 2012. Population Structure Of Adult Female Australian Sea Lions Is Driven By Fine-Scale Foraging Site Fidelity. Animal Behaviour, 83, 691-701.

Australian Government Department of the Environment and Energy. 2016. Biologically Important Areas of Regionally Significant Marine Species Dataset [2ed86f5a-4598-4ae9-924f-ac821c701003], Commonwealth of Australia, Australian Government Department of the Environment and Energy. Made Available Online at http://www.environment.gov.au/fed/catalog/search/resource.


Download the full account of the Houtman Abrolhos to Rottnest Shelf Waters IMMA using the Fact Sheet button below:

To make a request to download the GIS Layer (shapefile) for the Houtman Abrolhos to Rottnest Shelf Waters IMMA please complete the following Contact Form:

* Required fields

Please read the User Licence Agreement and IMMA Layer Metadata Description