Carter's freshwater mussel (Westralunio carteri)
|Size||Shell length: up to 10 cm (2) (3)|
Carter’s freshwater mussel is classified as Least Concern (LC) on the IUCN Red List (1).
Carter’s freshwater mussel (Westralunio carteri) is the only large freshwater bivalve to occur in south-western Australia. Its shell is generally oblong and smooth (3) (4), and is reddish-brown to almost black in colour (3).
Carter’s freshwater mussel was once found as far north as the Gascoyne River, southward and eastward to Esperance in Western Australia. However, it is now restricted to the Moore River basin, 80 kilometres north of Perth, and to the Kent River basin on the south coast, within 50 kilometres of the coast. There are also two outlying populations in the Goodga and Waychinicup Rivers (5).
Carter’s freshwater mussel occurs in greatest abundance is slower flowing parts of rivers and streams that have sediments that are soft enough for burrowing and stable enough so that the mussel does not sink. It is typically found among woody debris, leaf litter and exposed tree roots along the banks of rivers (3).
In addition, Carter’s freshwater mussel can also be found in landlocked freshwater lakes (3).
The eggs of Carter’s freshwater mussel undergo fertilisation within a specialised area of the female’s gills, known as a ‘marsupium’. After hatching, the larvae remain in the marsupium until they are ready to be released (4).
Like other freshwater mussels, Carter’s freshwater mussel has a life cycle which involves a parasitic stage during which the larvae, known as ‘glochidia’, attach to host fish for a period of three to four weeks during spring and summer, between late September to December (6). After they have completed metamorphosis, the newly formed juvenile mussels detach from their host fish and begin life in the sediments (7) (8).
Fish from wild populations found to have attached glochidia of Carter’s freshwater mussel primarily include endemic species such as the Swan River goby (Pseudogobius olorum), southwestern goby (Afurcagobius suppositus), western minnow (Galaxias occidentalis) and western pygmy perch (Nannoperca vittata) (6). A few introduced, non-native fish may also play host to the larvae of this species (6).
The lifespan of Carter’s freshwater mussel is not known, but other species in the Hyriidae family are estimated to live for up to 20 years or more (4).
The biggest threat facing Carter’s freshwater mussel is the salinisation (increased saltiness) of its formerly freshwater habitat (1) (3) (5) (9) (10) (11). This species has disappeared from areas that have been affected by dryland salinity (5) (9), with recent research showing that Carter’s freshwater mussel is intolerant of salinities above 3.0 parts per thousand (10).
Other potential threats to Carter’s freshwater mussel include livestock and urban development projects, which have been known to crush shells and also to contribute to severe erosion of river banks (4).
Although Carter’s freshwater mussel is currently classified as Least Concern (LC) on the IUCN Red List (1), new research suggests that the species may be more threatened than previously believed (5).
Carter’s freshwater mussel does not have any specific legal protection, but under the Western Australian Wildlife Conservation Act 1950, all native species are protected from exploitation. However, in contradiction to this, the Western Australian Fisheries Resources Management Act 1994 permits the taking of 30 mussels per day per fisherman without the need for a licence (12) (13) (14).
Beginning in 2010, a community education package was created for the purpose of involving the wider public in updating information on the distribution of Carter’s freshwater mussel. It also aimed to educate the public about the decline and conservation needs of south-western Australia’s freshwater ecosystems and about current research on Carter’s freshwater mussel (4).
A study into other factors which may limit the survival of Carter’s freshwater mussel is the subject of an ongoing investigation (15). Monitoring of its populations and habitats has also been recommended (1).
Find out more about Carter’s freshwater mussel and its conservation:
Mussel Watch Western Australia:
Information supplied and authenticated (23/05/12) by Michael Klunzinger, Murdoch University, Western Australia.
- Bivalve: a group of aquatic molluscs in which the soft parts are encased in a shell consisting of two parts, known as valves.
- Dryland salinity: the process by which a rising water table dissolves salts stored in the soil and brings them to the surface.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Fertilisation: the fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
- Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults, and in most cases are able to feed and move around but not able to reproduce.
- Metamorphosis: a distinct physical change from the larval to the adult form, or to another life stage.
- Parasitic: describes an organism that derives its food from, and lives in or on, another living organism at the host’s expense.
IUCN Red List (May, 2012)
- Klunzinger, M.W., Beatty, S.J., Allen, M.G. and Keleher, J. (2012) Mitigating the Impact of Serpentine Dam Works on Carter’s Freshwater Mussel. Freshwater Fish Group & Fish Health Unit, Murdoch University Report to the Department of Fisheries, Government of Western Australia.
- Morgan, D.L., Beatty, S.J., Klunzinger, M.W., Allen, M.G. and Burnham, Q.F. (2011) A Field Guide to Freshwater Fishes, Crayfishes and Mussels of South Western Australia. South East Regional Centre for Urban Landcare and Freshwater Fish Group & Fish Health Unit, Centre for Fish & Fisheries Research, Murdoch University, Perth.
Mussel Watch Western Australia (May, 2012)
- Klunzinger, M.W., Beatty, S.J., Morgan, D.L., Lymbery, A.J., Pinder, A.M. and Cale, D.J. (in press) Distribution of Westralunio carteri Iredale, 1934 (Bivalvia: Unionoida: Hyriidae) on the south coast of south-western Australia, including new records of the species. Journal of the Royal Society of Western Australia, 95(2).
- Klunzinger, M.W., Beatty, S.J., Morgan, D.L., Thomson, G.J. and Lymbery, A.J. (in press) Glochidia ecology in wild fish populations and laboratory determination of competent host fishes for an endemic freshwater mussel of south-western Australia. Australian Journal of Zoology.
- Bauer, G. and Wächtler, K. (2001) Ecology and Evolution of the Freshwater Mussels Unionoida. Springer-Verlag, New York.
- Strayer, D.L. (2008). Freshwater Mussel Ecology: A Multifactor Approach to Distribution and Abundance. University of California Press, Berkeley.
- Kendrick, G.W. (1976) The Avon: faunal and other notes on a dying river in south-western Australia. The Western Australian Naturalist: 13: 97-114.
- Klunzinger, M., Beatty, S. and Lymbery, A. (2010) Acute salinity tolerance of the freshwater mussel Westralunio carteri Iredale, 1934 of south-west Western Australia. Tropical Natural History, Suppl. 3: 112.
- Walker, K.F., Byrne, M., Hickey, C.W. and Roper, D.S. (2001) Freshwater mussels (Hyriidae) of Australia. In: Bauer, G. and Wächtler, K. (Eds.) Ecology and Evolution of the Freshwater Mussels Unionoida. Springer, New York.
Australian Legal Information Institute: Western Australian Consolidated Acts - Wildlife Conservation Act 1950 (May, 2012)
Western Australia Department of Fisheries (2011) Recreational Fishing Guide: South Coast Region. Department of Fisheries, Government of Western Australia, Perth. Available at:
Western Australia Department of Fisheries (2012) Recreational Fishing Guide: West Coast Region. Department of Fisheries, Government of Western Australia, Perth. Available at:
- Klunzinger, M.W. (in prep.) Biology and Ecology of Westralunio carteri IREDALE 1934, an Endemic Hyriid of South-western Australia. PhD Thesis, Murdoch University, Perth.