Eastern Dwarf Galaxias, Galaxiella pusilla (Mack 1936)


Other Names: Dwarf Galaxias, Dwarf Minnow, Eastern Little Galaxias, Striped Galaxias

A pair of Eastern Dwarf Galaxias, Galaxiella pusilla, from Tuerong Creek, Victoria. Source: Rudie H. Kuiter / Aquatic Photographics. License: All rights reserved

Summary:

A very small pale olive-brown galaxiid with a silvery-white belly, three faint dark stripes along the side, and a distinct v-shaped black mark often on the isthmus (fleshy area on the underside between the gill chambers), usually extending to near the pelvic-fin bases as two parallel dotted lines. Males have a bright orange mid-lateral stripe. Juveniles lack the distinct striped patterns and colour of adults, are predominantly pale olive to beige above, silvery-white below.

Populations have been dramatically affected by human induced changes such as the draining of swamps, and the species is now protected throughout its range.


Cite this page as:
Dianne J. Bray, Galaxiella pusilla in Fishes of Australia, accessed 25 Mar 2017, http://fishesofaustralia.net.au/home/species/3393

Eastern Dwarf Galaxias, Galaxiella pusilla (Mack 1936)

More Info


Distribution

Endemic to temperate freshwaters of coastal southeastern Australia, including Tasmania, from the Mitchell River Basin near Bairnsdale in eastern Victoria, westwards to south-east Melbourne, and Flinders Island in Bass Strait, and north-eastern and north-western Tasmania.

The Eastern Dwarf Galaxias inhabits both ephemeral and permanent still or gently flowing waters of roadside ditches, swamps and creek backwaters, usually with abundant submerged and emergent aquatic vegetation. Although typically preferring swampy floodplain habitats, they also occur in creeks and streams. 

Features

Dorsal fin 6-9 (usually 7-8); Anal fin 8-11 (usually 8-10); Pectoral fin  10-14 (usually 11-13); Pelvic fin  4-6 (usually 4-5); Gill rakers (first arch) 12-17 (usually 14-16).

Body elongate, stout, deeper at belly; body depth at vent 5.4-7.2 in SL; head small; snout short, blunt; jaws equal; sensory pores under lower jaw absent; Scales absent.

Caudal peduncle (tail base) with a low membranous fold almost to dorsal- and anal-fin rays; dorsal-fin small, originating far back on body behind level of anal fin; caudal fin rounded; pelvic fins small.

Size

Maximum length about 4 cm, commonly to 3.5 cm; females grow larger than males.

Colour

Adults are sexually dimorphic in colour. Both sexes are overall brownish-green to greenish-orange above, silvery white below with transparent fins. Males have three black stripes along each side with a bright orange stripe between the two lower black stripes. Females may have a golden midlateral stripe, and the black stripes are indistinct or absent.

Feeding

Omnivore - feeds on small insects, aquatic insect larvae, zooplankton including microcrustaceans, and some algae.

Biology

Eastern Dwarf Galaxias complete their entire lifecycle in freshwater. Although they may spawn year-round in favourable conditions, most spawning occurs during late winter to October. Females deposit a few small adhesive eggs (to 1.3 mm diameter) daily onto leaf litter and dense aquatic vegetation. The larvae hatch after 10-17 days at temperatures of 16-21°C.

The species is short-lived, with individuals reaching reproductive maturity in their first year and dying soon after spawning.


Conservation

  • EPBC Act 1999 : Vulnerable
  • IUCN Red List : Vulnerable
  • Tasmanian Threatened Species Protection Act 1995: Rare
  • Victorian Flora and Fauna Guarantee Act 1988: Threatened
  • The Eastern Dwarf Galaxias is listed as Threatened under the Victorian Flora and Fauna Guarantee Act 1988 (FFG Act), and is listed as Endangered in the Department of Environment, Land, Water and Planning (DELWP)’s Advisory List of Threatened Vertebrate Fauna in Victoria – 2013 (DSE 2013).

    Although locally abundant in some areas, the Eastern Dwarf Galaxias has a patchy distribution, and populations have been severely affected by human habitation, especially the draining of swamps and alterations to waterways. The species is also threatened by the spread of the introduced and invasive Eastern Gambusia, Gambusia holbrooki.

    Remarks

    Eastern Dwarf Galaxias appear to be adapted to survive for more than a week without surface water by finding refuge in burrows or amongst wet aquatic vegetation and detritus (Coleman et al. 2016).

    Similar Species

    Galaxiella pusilla differs from Galaxiella toourtkoourt in having a combination of the following characters: more vertebrae; a slightly longer caudal peduncle; more pronounced dorsal fin-anal fin setback, especially in females; and, adults are larger.

    Species Citation

    Galaxias pusillus Mack, 1936, Mem. Natl. Mus. Vict. 9: 101. Type locality: Cardinia Creek, Victoria.

    Author

    Dianne J. Bray

    Resources


    Eastern Dwarf Galaxias, Galaxiella pusilla (Mack 1936)

    References


    Allen, G.R. 1989 Freshwater fishes of Australia. T.F.H. Publications, Inc., Neptune City, New Jersey. 

    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.N. & Vanner, R.W. 1978. Observations on the biology of the dwarf galaxiid, Galaxiella pusilla (Mack) (Pisces: Galaxiidae). Vic. Nat. 95: 128-132.

    Berra TM, Allen GR (1989) Clarification of the differences between Galaxiella nigrostriata (Shipway, 1953) and Galaxiella munda McDowall, 1978 (Pisces: Galaxiidae) from Western Australia. Rec West Aust Mus 14: 293–297. 

    Cadwallader, P.L. & Backhouse, G.N. 1983. A Guide to the Freshwater Fish of Victoria. Government Printer, Melbourne. 

    Coleman, R.A. 2014. Conservation of the dwarf galaxias, Galaxiella pusilla (Mack 1936) (Teleostei: Galaxiidae), a threatened freshwater fish from south-eastern Australia. PhD Thesis, University of Melbourne, Parkville, 262 pp.

    Coleman, R.A., Hoffman, A.A. & Raadik, T.A. 2015. A review of Galaxiella pusilla (Mack) (Teleostei: Galaxiidae) in south-eastern Australia with a description of a new species. Zootaxa 4021(2): 243-281.

    Coleman, R.A., V. Pettigrove, T.A. Raadik, A.A. Hoffmann, A.D. Miller & M.E. Carew. 2010. Microsatellite markers and mtDNA data indicate two distinct groups in dwarf galaxias, Galaxiella pusilla (Mack) (Pisces: Galaxiidae), a threatened freshwater fish from south-eastern Australia. Conservation Genetics 11: 1911–1928. 

    Coleman RA, Raadik TA, Pettigrove V, Hoffmann AA. 2016. Taking advantage of adaptations when managing threatened species within variable environments: the case of the dwarf galaxias, Galaxiella pusilla (Teleostei, Galaxiidae). Marine and Freshwater Research - http://dx.doi.org/10.1071/MF15332 Abstract

    Coleman, R.A., A.R. Weeks & A.A. Hoffmann. 2013. Balancing genetic uniqueness and genetic variation in determining conservation and translocation strategies: a comprehensive case study of threatened dwarf galaxias, Galaxiella pusilla (Mack) (Pisces: Galaxiidae). Molecular Ecology doi: 10.1111/mec.12227

    Department of Environment, Land, Water and Planning 2015 Action statement No.258. Flora and Fauna Guarantee Act 1988. Dwarf Galaxias, Galaxiella pusilla. Department of Environment, Land, Water and Planning (DELWP) Victoria. 16 pp. PDF

    Humphries, P. 1983. Aspects of the Biology of the Dwarf Galaxiid, Galaxiella pusilla (Mack) (Salmoniformes: Galaxiidae). B.Sc. (Hons.) Thesis, Monash University 94 pp.

    Humphries, P. 1986. Observations on the ecology of Galaxiella pusilla (Mack) (Salmoniformes: Galaxiidae) in Diamond Creek, Victoria. Proc R Soc Vic 98: 133–137.

    Koster, W.M. 2003. Threatened fishes of the world: Galaxiella pusilla (Mack 1936) (Galaxiidae). Environmental Biology of Fishes 68: 268. 

    Kuiter, R.H. 2005. More on Dwarf Galaxias. Fishes of Sahul 19(3): 161–163.

    Mack G (1936) Victorian species of the genus Galaxias, with descriptions of two new species. Mem. Natl Mus. Vic. 9: 98–101.

    McDowall, R.M. 1978. A new genus and species of galaxiid fish from Australia (Salmoniformes: Galaxiidae). Journal of the Royal Society of New Zealand 8(1): 115-124.

    McDowall, R.M. 1978. Sexual Dimorphism in an Australian Galaxiid (Pisces: Galaxiidae). Report N0 328. Fisheries Research Division, Ministry of Agriculture and Fisheries, Christchurch.

    McDowall RM, Frankenburg RS (1981) The galaxiid fishes of Australia. Rec Aust Mus 33: 443–605.

    McDowall, R.M. & Fulton, W. 1996. Family Galaxiidae in McDowall, R.M. (ed.) Freshwater Fishes of South-eastern Australia. Sydney : Reed Books 247 pp.

    McDowall RM, Waters JM (2004) Phylogenetic relationships in a small group of diminutive galaxiid fishes and the evolution of sexual dimorphism. J R Soc N Z 34: 23–57.

    Merrick, J.R. & G.E. Schmida. 1984. Australian freshwater fishes: biology and management. Griffin Press Ltd., South Australia. 409 pp.

    Pen, L.J., Gill, H.S., Humphries, P. & Potter, I.C. 1993. Biology of the black-stripe minnow Galaxiella nigrostriata, including comparisons with the other two Galaxiella species. Journal of Fish Biology 43: 847–863. http://dx.doi.org/10.1111/j.1095-8649.1993.tb01160.x

    Raadik, T.A. 2006. Chapter 13 Freshwater Fishes, pp. 113–148. In Melbourne’s Wildlife. A Field Guide to the Fauna of Greater Melbourne. Museum Victoria and CSIRO Publishing, Melbourne. 

    Romanowski, N. 2004. Notes on dwarf Galaxias Galaxiella pusilla. Fishes of Sahul 18(4): 80-86.

    Saddlier S, Jackson J, Hammer M (2010) National Recovery Plan for the Dwarf Galaxias Galaxiella pusilla. Melbourne: State of Victoria Department of Sustainability and Environment. 21 pp.

    Stoessel, D. 2008. Assessment of the status of Dwarf Galaxias (Galaxiella pusilla) within the Hopkins, Barwon and Mitchell River Catchments, Victoria. Report for the Natural Heritage Trust. Arthur Rylah Institute for Environmental Research. Department of Sustainability and Environment, Heidelberg, Victoria.

    Stoessel, D., Pittman, K. and Tinkler, P. 2008. Distribution of Dwarf Galaxias (Galaxiella pusilla) in the West Gippsland Catchment, Victoria. Report for the West Gippsland Catchment Management Authority. Arthur Rylah Institute for Environmental Research. Department of Sustainability and Environment, Heidelberg, Victoria.

    Stoessel, D. 2010. Needle in a haystack: assessment of the status of Dwarf Galaxias (Galaxiella pusilla) at six sites in the West Gippsland Region, with reference to a pilot sampling protocol. Client report 2010/95 prepared for the West Gippsland Catchment Management Authority. Arthur Rylah Institute for Environmental Research, Department of Sustainability and Environment, Heidelberg, Victoria, 19 pp.

    Threatened Species Section. 2006. Recovery Plan: Tasmanian Galaxiidae 2006-2010. pp. 85. Department of Primary Industries and Water, Hobart, Tasmania.

    Tucceri, T. 2012. Conservation of Galaxiella pusilla re-visited. Fishes of Sahul 26(3): 694–700.

    Unmack PJ, Bagley JC, Adams M, Hammer MP, Johnson JB (2012) Molecular phylogeny and phylogeography of the Australian freshwater fish genus Galaxiella, with an emphasis on Dwarf Galaxias (G. pusilla). PLoS ONE 7(6): e38433. doi:10.1371/journal.pone.0038433

    Unmack, P.J. & Paras, G.J. 1995. Galaxiella pusilla: around Melbourne, going, going, nearly gone. Fishes of Sahul 9: 398–400.

    Wager, R. 1996. Galaxiella pusilla. The IUCN Red List of Threatened Species 1996: e.T8820A12934389. http://dx.doi.org/10.2305/IUCN.UK.1996.RLTS.T8820A12934389.en . Downloaded on 30 September 2015.

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    Quick Facts


    CAAB Code:37102011

    Conservation:EPBC Act Vulnerable; IUCN Vulnerable

    Conservation:TAS Vulnerable; VIC Vulnerable

    Habitat:Freshwater

    Max Size:4.8 cmSL; 5+ cmTL

    Native:Endemic

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