South Australian Gulfs and Adjacent Waters IMMA

Size in Square Kilometres

47,516 km2

Qualifying Species and Criteria

Australian sea lion – Neophoca cinerea

Criterion A; B (2); C (1, 2); D (1)

Southern right whale – Eubalaena australis

Criterion B (2); C (1, 3)

Indo-Pacific bottlenose dolphin – Tursiops aduncus

Criterion B (2)

Long-nosed fur seal – Arctocephalus forsteri

Criterion B (2)

Humpback whale – Megaptera novaeangliae

Criterion C (3)

Marine Mammal Diversity 

Orcinus orca, Kogia breviceps, Kogia sima, Balaenoptera acutorostrata, Tursiops truncatus, Hydrurga leptonyx, Delphinus delphis

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This IMMA includes Spencer Gulf, Gulf St Vincent bioregion and Investigator Strait, South Australia, and is located on the south-central coast of the continent. The unique oceanographic system includes the largest, south-facing inverse estuaries in the Southern Hemisphere. These are very shallow (<50 m), with high salinity and high water temperatures, especially in the north (Nunes Vaz 2014). Changes in sea levels have inundated/drained the region multiple times during the last several hundred thousand years (Cann et al. 1988), giving opportunities for evolutionary processes for marine mammals. This is especially true for inshore cetaceans such as the Indo-Pacific bottlenose dolphin, which has diverged from conspecifics elsewhere along the Australian coast (Jedensjo et al. 2020). Investigator Strait is a buffer zone between the gulfs and oceanic environments, being substantially influenced by the high-energy Southern Ocean to the south. A frontal system at the mouth of Spencer Gulf (within the IMMA) is likely to be an important feeding area for marine mammals, as are adjacent upwelling systems outside the IMMA. The Australian sea lion inhabits the IMMA and its two largest pupping colonies are located there (Goldsworthy et al. 2015). Females also utilise the IMMA as a feeding ground (Goldsworthy et al. 2009). Southern right whales migrate through the IMMA and have re-established calving sites in some locations. The Victor Harbor area is recognised as a small, established aggregation/calving site important for the recovery of the intensively-harvested, southeastern Australian sub-population (DSEWPaC 2012, Kemper et al. in prep.). Humpback whales also use the IMMA as migratory corridor, likely on their northward migration during autumn and winter (Kemper 2005). Other cetacean and pinniped species may be vagrants or occasional visitors based on the paucity of sighting and stranding records but more data are needed to confirm this. Some may use the IMMA as a temporary/seasonal feeding area (e.g. Kogia spp., killer whale) or simply be passing through (e.g. common bottlenose dolphin, blue whale).

Marine mammals in this IMMA are impacted in short- and long-term by human activities because it is the centre of the South Australian human population (Edyvane 1999). Expert elicitation identified noise, shipping, and net fishing as the greatest region-specific individual threats to marine mammals in Spencer Gulf with the common dolphin, Indo-Pacific bottlenose dolphin, and Australian sea lion showing particular susceptibility to these threats (Robbins et al. 2017). Mortality in fishing and aquaculture operations, shipping and recreational vessel strikes and illegal killing of dolphins are well documented (Segawa and Kemper 2015, Kemper and Gibbs 2001, Kemper et al 2008, Hamer et al. 2008). The semi-enclosed and slow-flushing nature of the region increases the risk of disease (Kemper et al. 2016) and exposure to chemical contamination (Lavery et al. 2009, Kemper et al. 2014).

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The Australian sea lion is listed as Endangered on the IUCN Red List. Population size is estimated at 9650 in South Australia with a small population in Western Australia and numbers in most colonies declining (Goldsworthy et al. 2015). Approximately 50 % of the species’ global population occurs in the IMMA.

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations 

Many haul-out and pupping sites of Australian sea lions are located within the IMMA. These pupping sites accounted for 60% of the estimated number of pups in South Australia in 2015 (Goldsworthy et al. 2015) and hence 50% of the global total. The IMMA includes the two largest aggregations of the species, at Dangerous Reef and The Pages islands. Australian sea lions are particularly susceptible to entanglement in gill nets (Hamer et al. 2013) and to a shark gill net fishery that operates within the region, with exclusion zones around all sea lion colonies in the IMMA (AFMA 2010).  Southern right whales have been aggregating in increasing numbers since the late 1990s in the Victor Harbor/Encounter Bay area in the southeastern part of the IMMA (Kemper et al. in prep.). Up to 25 whales can be seen each day during the austral autumn and winter. This exceeds other number of whales in the only other south-eastern Australian aggregation, at Warrnambool, Victoria. Fourteen small haul-out sites for the long-nosed fur seal are found in the IMMA, as well as three small breeding colonies. The area is inhabited by what is probably the largest proportion of the Indo-Pacific bottlenose dolphin population in southern Australia, and estimated numbers within the IMMA are about 3500 (Bilgmann et al. 2019).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The largest pupping colonies for Australian sea lions are located at The Pages and Dangerous Reef, both in the IMMA. These are two of only five breeding colonies globally that produce more than 100 pups each breeding season (Goldsworthy et al. 2015). The aggregation of southern right whales in the Victor Harbor area has recently been recognised as a small, established aggregation where a mean of 4.4 calving females are resident each year (Kemper et al. in prep.) and is significant for the southeastern Australian sub-population. The area is also frequently used by transient, unaccompanied adults and mating behaviour has been observed. Females with calves have also been observed within the inner parts of the gulfs (Kemper et al. 1997).

Sub-criterion C2: Feeding Areas

Australian sea lions feed in the benthic zone on the continental shelf, including within this IMMA. Foraging areas for lactating females are located near pupping colonies and are important to maintain pup condition in the first 18 months of their lives. In addition, the species displays Area Restricted Foraging for lactating adult females. The females from Dangerous Reef, in southern Spencer Gulf, undertook short duration feeding trips of 1.16 days (+/- 0.57 days) to an average maximum distance of 23.3 +/- 18.5 km, diving to the sea bed at 30–45 m soon after leaving the colony (Goldsworthy et al. 2009). Sea lions from Dangerous Reef feed on the bottom (Frangito 2013) on a wide variety of fish, sharks, rays, cephalopods and crustaceans based on DNA studies of faeces (Oxley 2019).

Sub-criterion C3: Migration Routes

Southern right whales migrate along the South Australian coast, generally in an east to west direction during winter (DSEWPaC 2012). These whales can stop-off in the IMMA and have been seen well within the gulfs, including at the far northern end of Spencer Gulf. Humpback whales have been seen in increasing numbers along the coast and within the IMMA during the last 30 years. It is likely that they are on their northward migration (Kemper 2005).

Criterion D: Special Attributes

Sub-criterion D1: Distinctiveness

Australian sea lions exhibit strong philopatry for pupping colonies (Lowther et al. 2012). The two largest colonies located within the IMMA are genetically distinct from those to the west of the region and the occupants use different foraging areas. There is strong evidence that foraging specialization within discrete fine-scale foraging areas and habitats at the individual level limit the dispersive capacity of adult female Australian sea lions, which in turn drives population structure.

Supporting Information

Australian Fisheries Management Authority (AFMA) (2010). Australian sea lion management strategy; Southern and Eastern Scalefish and Shark Fishery (SESSF). Australian Fisheries Management Authority, Canberra.

Bannister, J. L. (2017). Project A7—Monitoring population dynamics of south‐western right whales off southern Australia 2015–2018. Final report to National Environment Science Program, Australian Commonwealth Government.

Bilgmann, K., Moller, L. M., Harcourt, R. G., Gibbs, S. E. & Beheregaray, L. B. (2007). Genetic differentiation in bottlenose dolphins from South Australia: association with local oceanography and coastal geography. Mar Ecol Prog Ser 341, 265–276.

Bilgmann, K., Parra, G. P., Zanardo, N., Beheregaray, L. B., Moller, L. M. (2014) Multiple management units of short-beaked common dolphins subject to fisheries bycatch off southern and southeastern Australia. Marine Ecology Progress Series 500:269-279.

Bilgmann, K., Parra, G. J., Holmes, L., Peters, K. J., Jonsen, I. D., Moller, L. M. (2019) Abundance estimates and habitat preferences of bottlenose dolphins reveal the importance of two gulfs in South Australia. Scientific Reports 9:8044.

Cann, J. H., Belperio, A. P. Gostin, V. A., Murray-Wallace, C. V. (1988) Sea level history, 45,000 to 30,000 y B.P. inferred from benthic foramina, Gulf St Vincent, South Australia. Quaternary Research 29:153-175.

Carroll, E., Alexander, A., Patenaude, N., Steel, D., Harcourt, R., Childerhouse, S., … Baker, C. S. (2011). Population structure and individual movement of southern right whales around New Zealand and Australia. Marine Ecology Progress Series, 437, 257–268.

Department of Sustainability, Environment, Water, Population and Communities (DSEWPaC) (2012). Conservation Management Plan for the Southern Right Whale: A Recovery Plan under the Environment Protection and Biodiversity Conservation Act. 1999 (2011–2021), Available at:

Edyvane, K. (1999) Coastal and marine wetlands in Gulf St Vincent, South Australia: understanding their loss and degradation. Wetlands Ecology and Management 7:83-104.

Filby, N., Bossley, M., Sanderson, K. J., Martinez, E., Stockin, K. A. (2010) Distribution and population demographics of common dolphins (Delphinus delphis) in the Gulf St Vincent, South Australia. Aquatic Mammals 36:33-45.

Frangito, K. (2013). Feeding behaviour and habitat utilisation of adult female Australian sea lions (Neophoca cinerea) using animal-borne video cameras. BSc (Hons) thesis, University of Adelaide, Adelaide, South Australia.

Gibbs, S. E. and C. M. Kemper (2014) Whales and dolphins in Spencer Gulf. Chapter 17 In: Natural History of Spencer Gulf (Eds S.A. Shepherd, S. Madigan, B. M. Gillanders, S. Murray-Jones, & D. Wiltshire) pp. 242–253 (Royal Society of South Australia, Adelaide).

Goldsworthy, S. D., Page, B., Shaughnessy, P. D., Hamer, D., Peters, K. D., McIntosh, R. R., Baylis, A. M. M. and McKenzie, J. (2009). Innovative solutions for aquaculture planning and management: addressing seal interactions in the finfish aquaculture industry. FRDC Project number: 2004/201 Final report. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication Number F2008/000222-1. SARDI Research Report Series No. 288. 291 pp. ISBN: 978-0-7308-5391-6.

Goldsworthy, S. D., Page, B., Shaughnessy, P. D., & Linnane, A. (2010). Mitigating Seal Interactions In The SRLF And The Gillnet Sector SESSF In South Australia. Report to The Fisheries Research And Development Institute. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. Sardi Publication No. F2009/000613-1, SARDI Research Report Series No. 405. ISBN: 978-1-921563-26-3.

Goldsworthy, S. D., Mackay, A. I., Shaughnessy, P. D., Bailleul, F., Holman, D. (2015) Maintaining and monitoring of pup production at key Australian sea lion colonies in South Australia (2014/2015). SARDI Research Report Series No. 871.

Hamer, D. J., Ward, T. M., McGarvey, R. (2008) Measurement, management and mitigation of operational interactions between the South Australian Sardine Fishery and the short-beaked common dolphin (Delphinus delphis). Biological Conservation 141: 2865-2878.

Hamer D. J., Goldsworthy, S. D., Costa, D. P., Fowler, S. L., Page, B. and Sumner, M. D. (2013). The endangered Australian sea lion regularly becomes by-catch in and extensively overlaps with demersal shark gill-nets in South Australia. Biological Conservation 157, 386–400.   DOI: 10.1016/j.biocon.2012.07.010.

Jedensjo, M. (2019) Combining genetics and morphology to resolve a long standing taxonomic issue: How many bottlenose dolphin species are there in Australian waters. University of Zurich. PhD thesis

Jedensjö, M., Kemper, C. M., Milella, M., Willems,E. P., and Krützen, M. (2020) Taxonomy and distribution of bottlenose dolphins (genus Tursiops) in Australian waters: an osteological clarification. Canadian Journal of Zoology 98: 461–479.

Kemper, C. M., Mole, J., Warneke, R. M., Ling, J.K., Needham, D. J. and Wapstra, J. E. (1997) Southern Right Whales in southeastern Australia¾aerial surveys during 1991-93 and incidental information from 1904.  Pp. 40-55 in Marine mammal research in the Southern Hemisphere Volume 1: status, ecology, and medicine edited by Hindell, M. and Kemper, C. M.  Surrey Beatty & Sons, Chipping Norton. 186 pp.

Kemper, C. M, and Gibbs, S. E. (2001) Dolphin interactions with tuna feedlots at Port Lincoln, South Australia and recommendations for minimising entanglements. Journal of Cetacean Research and Management 3: 283-292.

Kemper, C. M. (2005) Records of humpback whales Megaptera novaeangliae in South Australia. Transactions of the Royal Society of South Australia 129(1): 53–58.

Kemper, C., Bossley, M. and Shaughnessy, P. (2008).  Marine mammals of Gulf St Vincent, Investigator Strait and Backstairs Passage.  Pp 339-352 in Natural History of Gulf St Vincent. (Eds S. Shepherd, S. Bryars, I. R. Kirkegaard, P. Harbison, and J. T. Jennings).  Royal Society of South Australia: Adelaide.

Kemper, C. M., Middleton, J. F. and van Ruth, P. D. (2013) Association between Caperea marginata and areas of high marine productivity off Australia and New Zealand. New Zealand Journal of Zoology 40 (2): 102–128.

Kemper, C., D. Stemmer, T. Reardon, G. Medlin, P. D. Shaughnessy and H. Owens (2014) Mammals. In ‘Census of South Australian Vertebrates’ (Ed. H. Owens & A. Graham). (Department of Environment, Water and Natural Resources, South Australia and South Australian Museum). Available at:

Kemper, C. M., I. Tomo, J. Bingham, S. S. Bastianello, J. Wang, S. E. Gibbs, L. Woolford, C. Dickason, and D. Kelly. 2016. Morbillivirus-associated unusual mortality event in South Australian bottlenose dolphins is largest reported for the Southern Hemisphere. Royal Society Open Science 3: 160838.

Kemper, C. M., Steele-Collins, E., Charlton, C., Al-Humaidhi, A., Segawa Fellowes, T., Marsh, O. (in prep) Encounter Bay, South Australia, an important aggregation and calving site for the southern right whale, Eubalaena australis.

Lavery, P. J., Kemper, C. M., Sanderson, K., Schultz, C. G., Coyle, P., Mitchell, J. G. and Seuront, L.  (2009) Heavy metal toxicity of kidney and bone tissues in South Australian adult bottlenose dolphins (Tursiops aduncus).  Marine Environmental Research 67: 1–7.

Lowther, A. D., Harcourt, R. G., Goldsworthy, S. D. and Stow, A. (2012). Population structure of adult female Australian sea lions is driven by fine-scale foraging site fidelity. Animal Behaviour 83, 691–701.

Nunes Vaz, R. A. (2014) Physical characteristics of Spencer Gulf, Chapter 4 in Natural History of Spencer Gulf (Eds S.A. Shepherd, S. Madigan, B. M. Gillanders, S. Murray-Jones, & D. Wiltshire) Royal Society of South Australia. Pp. 44-68.

Oxley, A. P. A. (2019). Dietary assessment of seal populations in South Australia using a new molecular (metabarcoding) tool. Pp. 77-131. In: Goldsworthy, S. D., Bailleul, F., Nursey-Bray, M., Mackay, A., Oxley, A., Reinhold, S.-L., and Shaughnessy P. D. Assessment of the impacts of seal populations on the seafood industry in South Australia. Final report to the Fisheries Research and Development Corporation, Project No. 2013/011. ISBN: 978-1-876007-16-4.

Pratt EAL, Beheregaray LB, Bilgmann K, Zanardo N, Diaz-Aguirre F, Möller LM. (2018). Hierarchical metapopulation structure in a highly mobile marine predator: the southern Australian coastal bottlenose dolphin (Tursiops cf. australis). Conserv Genet. 19(3):1–18.

Robbins, W. D., C. Huveneers, G. J. Parra, L. Möller, and B. M. Gillanders. (2017). Anthropogenic threat assessment of marine-associated fauna in Spencer Gulf, South Australia. Marine Policy 81:392-400.

Sekiguchi K, Best PB, Kaczmaruk BZ 1992. New information on the feeding habits and baleen morphology of the pygmy right whale Caperea marginata. Marine Mammal Science 8: 288–293.

Segawa, T. and Kemper, C. (2015) Cetacean strandings in South Australia (1881–2008). Australian Mammalogy 37: 51–66.

Stamation, K., Watson, M., Maloney, P., Charlton, C., & Bannister, J. (2020). Population estimate and rate of increase of southern right whales Eubalaena australis in southeastern Australia. Endangered Species Research 41: 373-383.


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