Balston's Pygmy Perch, Nannatherina balstoni Regan 1906

Other Names: Balston's Perchlet, King River Perchlet

Balston's Pygmy Perch, Nannatherina balstoni. Source: Mark Allen / Murdoch University. License: All rights reserved


A relatively large and rare pygmy perch found only in a small area of coastal peat flats in the extreme southwest corner of Western Australia.

Balston's Pygmy Perch is brownish above, silvery below, with a cross-hatched pattern formed from a midlateral stripe and a series of vertical bars.

Video of Balston's Pygmy Perch

Cite this page as:
Bray, D.J. & Thompson, V.J. 2018, Nannatherina balstoni in Fishes of Australia, accessed 21 Apr 2024,

Balston's Pygmy Perch, Nannatherina balstoni Regan 1906

More Info


Historically known only from the south west coast of Western Australia from Goodga River to Gin Gin Brook. Inhabits acidic and tannin-stained freshwater pools, streams and lakes in sandy areas within 30 km of the coast. Usually found in shallow water amongst tall sedge thickets.

The species has disappeared from river systems and wetlands north of the Margaret River, and is now only found in drainage systems and wetlands between Margaret River and Two People's Bay.

Over the past few years, Mark Allen, David Morgan and Stephen Beatty from Murdoch University’s Freshwater Fish Group and Fish Health Unit surveyed a number of catchments where Balston's Pygmy Perch historically occurred. They found that the species has disappeared about one-quarter of those catchments, and only occurs in relatively pristine freshwater systems.


Dorsal fin VII-VIII, 9-11; Anal fin III, 8-10; Pectoral fin 12-13; Pelvic fin I, 5; Gill rakers (all rudimentary) 3-7; Lateral line scales 2-17 (interrupted series); Mid-lateral scales 34-38; Transverse scale rows 15-16.

Body relatively slender, greatest body depth 3.4-4.0 in SL; mouth relatively large, jaws reaching to below posterior part of eye; rear edge of preorbital hidden under skin; scales cycloid.

Dorsal fin single, deeply notched; anal fin large, below posterior part of dorsal fin; pelvic fin rounded; pectoral fin moderately large; caudal fin truncate to rounded.


To 9 cm SL, commonly to 6 cm.


Mainly dark brown with some paler blotching, whitish ventrally; some specimens with darker brown mid-lateral stripe bordered above and below with broad yellow-white blotches or stripes; fins dusky to clear, soft dorsal, caudal, and anal fins with brown spotting.


The larvae and juveniles feed on zooplankton (mostly crustacean larvae, and also fly larvae) which is abundant during winter and spring. From a size of about 25mm, juveniles and adults feed mostly on terrestrial spiders and insects taken from the water surface, as well as on insect larvae.


Balston's Pygmy perch typically has a one-year life cycle. Spawning occurs in response to flooding from June to early September with a mid-winter peak when water levels are at their highest. Over a period of several weeks, females deposit batches of eggs each day amongst aquatic vegetation. Females lay between 500 and 1600 eggs, and the larvae hatch after 2-4 days.


  • EPBC Act 1999 : Vulnerable
  • IUCN Red List : Data Deficient
  • WA Wildlife Conservation Act 1950: Schedule 1. The species is protected in WA and may not be taken.
  • The distribution of Balston’s Pygmy Perch has contracted markedly in relatively recent times. The species has disappeared from all rivers between the Moore River and the Margaret River and remaining populations are extremely fragmented. N. balstoni is now seems only to occur in ~69% of its historical distribution. The species no longer occurs in the King River system (the type locality).

    Factors in the range decline of this species include: increasing salinity, land clearing and habitat degradation, decreased and altered water flows due to climate change and the removal of water for irrigation, barriers to migration and introduced feral fishes.

  • Remarks

    Only one syntype remains. Based on a review of published information and unpublished data held by the authors, Co-occurs with the Western Pygmy Perch, Nannoperca vittata, and the Little Pygmy Perch, Nannoperca pygmaea.

    Similar Species

    Balston's Pygmy Perch is the only species in the genus Nannatherina, and can be easily distinguished from Nannoperca vittata by differences fin ray counts, a larger mouth size and a more slender body.


    The species is named for W.E. Balston who presented the first specimens to the British Museum in 1906.

    Species Citation

    Nannatherina balstoni Regan, 1906, Ann. Mag. Nat. Hist (7)18(70): 451. Type locality: King River, WA.


    Bray, D.J. & Thompson, V.J. 2018

    Balston's Pygmy Perch, Nannatherina balstoni Regan 1906


    Allen, G.R. 1982. Inland Fishes of Western Australia.  Perth: Western Australian Museum 86 pp.

    Allen, G.R. 1989. Freshwater Fishes of Australia.  Neptune, New Jersey: T.F.H. Publications pp. 1-240

    Allen, G.R., Midgley, S.H. & Allen, M. 2002. Field guide to the freshwater fishes of Australia.  Perth: Western Australian Museum 394 pp.

    Allen, G.R., I.C. Potter & R. Lenanton 1994. Proposed addition deletion or change to the schedules of declared threatened or specially protected fauna or the reserve list Nannatherina balstoni. Perth: Department of Conservation and Land Management.

    Beatty, S.J., Morgan, D.L., Rashnavadi, M. & Lymbery, A.J. 2011 Salinity tolerances of endemic freshwater fishes of south-western Australia: implications for conservation in a biodiversity hotspot. Marine & Freshwater Research 62: 91-100.

    Gill, H.S. & Morgan, D.L. 1998. Larval development of Nannatherina balstoni Regan (Nannopercidae), with a description of ontogenetic changes in diet. Ecology of Freshwater Fish 7: 132-139.

    Jerry, D.R., Elphinstone M.S. & Baverstock, P.R. 2001. Phylogenetic relationships of Australian members of the family Percichthyidae inferred from mitochondrial 12S rRNA sequence data. Molecular Phylogenetics and Evolution 18: 335–347.

    Kuiter, R. & Allen, G.R. 1986. A synopsis of the Australian pygmy perches (Percichthyidae), with the description of a new species. Revue fr. Aquariol 12: 109–116.

    Kuiter, R.H., Humphries, P.A. & Arthington, A.H. 1996. Pygmy Perches. In: McDowall, R.M. (Ed.), Freshwater Fishes of Southeastern Australia. Reed Books, Chatswood, Sydney, pp 168–175.

    Merrick, J.R. & Schmida, G.E. 1984. Australian Freshwater Fishes Biology and Management.  Sydney: J.R. Merrick 409 pp.

    Morgan, D.L. 2009. Threatened fishes of the world: Nannatherina balstoni Regan 1906 (Nannopercidae). Environmental Biology of Fishes 84: 409-410.

    Morgan, D.L., Beatty, S.J., Allen, M.G., Keleher, J.J. & Moore, G.I. 2014. Long live the King River Perchlet (Nannatherina balstoni). Journal of the Royal Society of Western Australia 97: 307–312.

    Morgan, D.L., Beatty, S.J., Klunzinger, M.W., Allen, M.G. & Burnham, Q.E. 2011. A Field Guide to Freshwater Fishes, Crayfishes & Mussels of South-Western Australia. SERCUL & Freshwater Fish Group & Fish Health Unit (Murdoch University), Murdoch, Western Australia. 80 pp.

    Morgan, D.L., Gill, H.S. & Potter, I.C. 1995. Life cycle, growth and diet of Balston's pygmy perch in its natural habitat of acidic pools in south-western Australia. Journal of Fish Biology 47: 808-825.

    Morgan, D.L., Gill, H.S. & Potter, I.C. 1996. Distribution of freshwater fish in the south-western corner of Western Australia. Water Resource Technical Series, Water and Rivers Commission Report WRT4.

    Morgan, D.L., Gill, H.S. & Potter, I.C. 1998. Distribution, identification and biology of freshwater fishes in southwestern Australia. Records of Western Australian Museum Supplement 56: 1–97.

    Pusey, B.J. & Edward, D.H.D. 1990. Structure of fish assemblages in waters of the southern acid peat flats, south-western Australia. Australian Journal of Marine & Freshwater Research 41: 721–734.

    Regan, C.T. 1906. A collection of fishes from the King River, Western Australia. Ann. Mag. Nat. Hist(7)18(70): 450-453.

    Webster, H.O. 1949. Occurrence of King River Perchlet in the Margaret River. The Western Australian Naturalist 2(2): 46.

    Whitley, G.P. 1947. The fluvifaunulae of Australia with particular reference to the freshwater fishes in Western Australia. The Western Australian Naturalist 1(3): 49–53.

    World Conservation Monitoring Centre 1996. Nannatherina balstoni. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. . Downloaded on 14 March 2012.

    Quick Facts

    CAAB Code:37311217

    Conservation:EPBC Act Vulnerable; IUCN Data Deficient

    Conservation:WA Vulnerable

    Habitat:Freshwater streams, lakes, wetlands

    Max Size:9 cm SL


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