Murray Hardyhead, Craterocephalus fluviatilis McCulloch 1912

Other Names: Mitchellian Freshwater Hardyhead, Mitchellian Hardyhead, Western Crat, Western Freshwater Hardyhead

Murray Hardyhead, Craterocephalus fluviatilis. Source: Gunther Schmida. License: CC BY Attribution-Noncommercial-ShareAlike


A small, silvery-green to dark golden hardyhead with almost circular scales, a reticulated pattern along the back formed by dark scale margins, a pale silvery to golden belly, and a distinct mid-lateral stripe.

Video of Murray Hardyhead conservation and recovery efforts in the Victorian Mallee region.

Cite this page as:
Bray, D.J. & Thompson, V.J. 2022, Craterocephalus fluviatilis in Fishes of Australia, accessed 17 Jun 2024,

Murray Hardyhead, Craterocephalus fluviatilis McCulloch 1912

More Info


Endemic to the mid and lower Murray-Darling River system in south-eastern Australia. Historically the species occurred as far upstream as Narrandera on the Murrumbidgee River, Wentworth on the lower Darling River, New South Wales; in multiple wetlands near Swan Hill and Mildura in Victoria; sections of the Murray River and its tributaries near Renmark, Swan Reach and the Lower Lakes near the Murray River mouth and lower reaches of Eastern Mount Lofty tributary streams, South Australia. 

Over the past five decades, the species has dramatically declined in distribution and abundance, and scientists fear that the Murray Hardyhead is on the verge of extinction.

Remnant populations now only occur in the Lower Murray Region and Lower Lakes Region of South Australia. In Victoria, until recently, the Murray Hardyhead is found in Round Lake, Woorinen North Lake and Cardross Lakes, along with some salt lakes, irrigation channels and creeks in northern Victoria. No viable populations have been found in New South Wales for some time. The species has been recorded in freshwater wetlands in South Australia, although in Victoria, remnant populations of Murray Hardyhead occur in saline habitats.

Murray Hardyhead school in open water habitats, preferring relatively salty fringing wetlands in floodplains and lakes. Historically they survived in isolated wetlands on floodplain fringes during dry seasons, dispersing out over the floodplain during wet seasons. 


Dorsal fin IV-VII + I, 5-8; Anal fin I, 6-9; Pectoral fin 11-13. 

Body laterally compressed, moderately deep and elongate; greatest body depth 4.0-5.1 in SL; mouth small, protrusible, lips not thick, gape restricted by labial ligament from one third to half way along premaxilla; teeth small, in single row and restricted to anterior part of both jaws; rear edge of jaw does not reach eye; eye diameter 3.2-3.9 in HL.

Scales on body small, thin, deciduous, almost circular, with circuli obvious and complete; scales on top head large and irregularly shaped; vertical scale rows 31-35; horizontal scale rows 10-12.

Two small, separate, short-based dorsal fins; origin of 2nd dorsal fin directly above anal fin; caudal fin forked; pectoral fins positioned high on sides; pelvic fins abdominal.


To 7cm SL


Silvery to golden above, paler with a silvery sheen below, a silvery dark mid-lateral stripe, and a reticulate pattern above formed by dark scale margins. The fins become bright yellow during spawning.


Omnivore - feeds on micro-crustaceans, aquatic insects (midge and mosquito larvae), and algae.


The Murray Hardyhead is primarily an annual species (i.e. most fish reach maturity, spawn and die within a year), and spawns from September to April, mostly during late spring to early summer.Females deposit batches of eggs with adhesive filaments amongst aquatic vegetation, particularly Eel Grass.


IUCN Red List: Critically Endangered

The major threats to remaining Murray Hardyhead populations are habitat degradation, the impact of non-native species such as Eastern Gambusia, European Carp, and Redfin, drought, salinity, and the regulation of rivers and creation of barriers to dispersal.


Adams et al. (2011) found that Craterocephalus fluviatilis comprised four genetically distinct populations.
Historically the species has been confused with a number of species including C. eyresii and C. amniculus (Crowley and Ivanstoff 1990 However, only the latter species is also found in the southern tributaries of the Murray-Darling Basin (Ivanstoff and Crowley 1996).

Similar Species

Historically the Murray Hardyhead had been confused with a number of species, including Craterocephalus amniculus,  C. eyresii, and C. fulvus. Crowley and Ivantsoff (1990) revised the genus, recognising C. fluviatilis as valid. This is the only species found in the southern tributaries of the Murray-Darling Basin (Ivanstoff and Crowley 1996). C. fluviatilis differs from C. eyresii and the Darling Hardyhead, C. amniculus, in scale counts, body depth and in having a single row of inward pointing teeth in the upper and lower jaw.


The specific name is from the Latin fluviatilis (= of or belonging to a river), in reference to the habitat of this species.

Species Citation

Craterocephalus fluviatilis McCulloch, 1912. Proc. R. Soc. Qld. 24: 49, pl. 1(1). Type locality: North Yanko Creek, Narranderra, New South Wales.


Bray, D.J. & Thompson, V.J. 2022


Atlas of Living Australia

Murray Hardyhead, Craterocephalus fluviatilis McCulloch 1912


Adams, M., Wedderburn, S.D., Unmack, P.J., Hammer, M.P. & Johnson, J.B. 2011. Use of Congeneric Assessment to Reveal the Linked Genetic Histories of Two Threatened Fishes in the Murray-Darling Basin, Australia. Conservation Biology 25: 767–776.

Allen, G.R. 1989. Freshwater Fishes of Australia. Neptune, New Jersey : T.F.H. Publications 240 pp., (as Craterocephalus eyresii, in part) 

Allen, G.R., Midgley, S.H. & Allen, M. 2002. Field Guide to the Freshwater Fishes of Australia. Perth : Western Australian Museum 394 pp.

Backhouse, G., Lyon, J. & Cant, B. 2008. National Recovery Plan for the Murray Hardyhead Craterocephalus fluviatilis. Department of Sustainability and Environment, Melbourne. See ref online

Backhouse, G., Lyon, J. & Cant, B. 2008. Background and Implementation Information for the Murrray Hardyhead Craterocephalus fluviatilis National Recovery Plan. Department of Sustainability and Environment, Melbourne, 16 pp. See ref online

Cadwallader, P.L. & Backhouse, G.N. 1983. A Guide to the Freshwater Fish of Victoria. Melbourne : F.D. Atkinson Government Printer 249 pp. figs.

Chessman, B.C. & Williams, W.D. 1974. Distribution of fish in inland saline waters of Victoria, Australia. Australian Journal of Marine and Freshwater Research 25: 167–172.

Crowley, L.E.L.M. & Ivantsoff, W. 1990. A review of species previously identified as Craterocephalus eyresii (Pisces: Atherinidae). Proceedings of the Linnaean Society of New South Wales 112(2): 87-103.

Crowley, L.E.L.M. & Ivantsoff, W. 1992. Redefinition of the freshwater fish genus Craterocephalus (Teleostei: Atherinidae) of Australia and New Guinea with an analysis of three species. Ichthyological Exploration of Freshwaters 3(3): 273–287.

Ebner, B., Raadik, T. & Ivantsoff, W. 2003. Threatened fishes of the world: Craterocephalus fluviatilis McCulloch, 1913 (Atherinidae). Environmental Biology of Fishes 68: 390.

Ellis, I., Stoessel, D., Hammer, M., Wedderburn, S., Suitor, L. & Hall, A. 2013. Conservation of an inauspicious endangered freshwater fish, Murray hardyhead (Craterocephalus fluviatilis), during drought and competing water demands in the Murray–Darling Basin, Australia. Marine and Freshwater Research 64: 792-806

Gilligan, D. 2005. Fish Communities of the Murrumbidgee Catchment: Status and Trends. NSW Department of Primary Industries – Final Report Series No. 75.

Hammer, M.P., Adams, M. & Foster, R. 2012. Update to the catalogue of South Australian freshwater fishes (Petromyzontida & Actinopterygii). Zootaxa 3593: 59-74.

Hammer, M.P., Bice, C.M., Hall, A., Frears, A., Watt, A., Whiterod, N.S., Beheregaray, L.B., Harris, J.O. & Zampatti, B.P. 2013. Freshwater fish conservation in the face of critical water shortages in the southern Murray-Darling Basin, Australia. Marine and Freshwater Research 64: 807-21.

Hammer, M. & Wedderburn, S. 2008. The threatened Murray Hardyhead: natural history and captive rearing. Fishes of Sahul 22: 390–399.

Harris, J.H. & Gehrke, P.C. 1997. Fish and Rivers in Stress: the NSW Rivers Survey. NSW Fisheries, Cronulla.

Humphries, P. 2004. Blandowski misses out: Ichthyological etiquette in 19th-century Australia. Endeavour 27: 160-165.

Ivantsoff, W. & Crowley, L.E.L.M. 1996. Silversides or hardyheads, pp. 123-133. in McDowall, R.M. (ed.)  Freshwater Fishes of South-eastern Australia.  Reed, Sydney.  

Ivantsoff, W., Crowley, L.E.L.M. & Allen, G.R. 1987. Description of three new species and one subspecies of freshwater hardyhead (Pisces: Atherinidae: Craterocephalus) from Australia. Records of the Western Australian Museum 13(2): 171-188.  

Kuiter, R.H. 2013. Pictorial Guide to Victoria's Freshwater Fishes. Seaford, Victoria : Aquatic Photographics 178 pp.  

Kuiter, R.H. 2018. Pictorial guide to Victoria's freshwater fishes. Part 1. E-version. Seaford, Victoria : Aquatic Photographics 1-110.  

Lintermans, M. 2007. Fishes of the Murray-Darling Basin: An introductory guide. Murray-Darling Basin Commission, Canberra. 157 pp.  

Llewellyn, L.C. 1979. Some observations on the spawning and development of the Mitchellian freshwater hardyhead Craterocephalus fluviatilis McCulloch from inland waters in New South Wales. Australian Zoologist 20: 269-288.  

Lloyd, L.N. & Walker, K.F. 1986. Distribution and conservation status of small freshwater fish in the River Murray, South Australia. Transactions of the Royal Society of South Australia 110: 49–57.   

Lyon, J. & Ryan, T. 2005. Observations of the nationally threatened freshwater fish, Murray Hardyhead Craterocephalus fluviatilis McCulloch 1913, in three Victorian salt lakes. The Victorian Naturalist 122(2): 78-84.  

McCulloch, A.R. 1912. Notes on some Australian Atherinidae. Proceedings of the Royal Society of Queensland 24: 47–53. See ref at BHL

McDowall, R.M. 1996. Freshwater Fishes of South-eastern Australia.  Sydney : Reed Books 2nd Ed.  247 pp.

Stoessel, D., Ellis, I.M., Whiterod, N., Gilligan, D., Wedderburn, S.D. & Bice, C. 2019. Craterocephalus fluviatilis. The IUCN Red List of Threatened Species 2019: e.T40692A123379212. Downloaded on 21 October 2020.

Stoessel, D., Fairbrother, P., Fanson, B., Nicol, M., Raadik, T., Dodd, L. & Raymond, S. 2018. Addressing critical knowledge gaps to improve conservation outcomes for Murray hardyhead (Craterocephalus fluviatilis). A project of the Biodiversity On-ground Actions Regional Partnerships and Targeted Actions program. Arthur Rylah Institute for Environmental Research, Department of Environment, Land, Water and Planning, Heidelberg.

Thiele, S., Adams, M., Hammer, M., et al. 2020. Range-wide population genetics study informs on conservation translocations and reintroductions for the endangered Murray hardyhead (Craterocephalus fluviatilis). Aquatic Conservation: Marine and Freshwater Ecosystems 30: 1959-1974.

Unmack, P.J. & Dowling, T.E. 2010. Biogeography of the genus Craterocephalus (Teleostei: Atherinidae) in Australia. Molecular Phylogenetics and Evolution 55: 968-984.

Wedderburn, S.D. 2008. Population fragmentation in the Murray Hardyhead Craterocephalus fluviatilis McCulloch, 1912 (Teleostei: Atherinidae): Ecology, Genetics and Osmoregulation. Ph.D. Thesis, School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia.

Wedderburn, S.D., Hammer, M.P. & Bice, C.M. 2012. Shifts in small-bodied fish assemblages resulting from drought-induced water level recession in terminating lakes of the Murray–Darling Basin, Australia. Hydrobiologia 691: 35–46. 

Wedderburn, S.D., Hillyard, K.A. & Shiel, R.J. 2013. Zooplankton response to flooding of a drought refuge and implications for the endangered fish species Craterocephalus fluviatilis cohabiting with alien Gambusia holbrookiAquatic Ecology 47: 263.

Wedderburn, S.D. & Walker, K.F. 2008. Osmoregulation in populations of an endangered hardyhead (Atherinidae: Craterocephalus fluviatilis McCulloch, 1912) from different salinity regimes. Ecology of Freshwater Fish 17: 653–658. 

Wedderburn, S.D., Walker, K.F. & Zampatti, B.P. 2007. Habitat separation of Craterocephalus (Atherinidae) species and populations in off-channel areas of the lower River Murray, Australia. Ecology of Freshwater Fish 16: 442–449.

Wedderburn, S.D., Walker, K.F. & Zampatti, B.P. 2008. Salinity may cause fragmentation of hardyhead (Teleostei: Atherinidae) populations in the River Murray, Australia. Marine and Freshwater Research 59: 254–258.

Quick Facts

CAAB Code:37246020

Conservation:IUCN Critically Endangered

Habitat:Freshwater (rel. saline)

Max Size:8 cm TL


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CAAB distribution map