Flyspecked Hardyhead, Craterocephalus stercusmuscarum (Günther 1867)

Other Names: Fly-specked Hardyhead, Freshwater Hardyhead, Freshwater Silverside, Line-eye, Mitchellian Hardyhead, Northern Fresh Water Hardyhead, Speckled Crat, Worrell's Freshwater Hardyhead

Flyspecked Hardyhead, Craterocephalus stercusmuscarum. Source: Neil Armstrong. License: All rights reserved

The Flyspecked Hardyhead is widespread in northern Australia. They are brownish with a series of small dark spots above and below the dark mid-lateral stripe. Breeding males have a yellow belly, while females have a dark blotch near the anus.

Video of  Flyspecked Hardyheads in the South Alligator River catchment in Kakadu National Park.

Cite this page as:
Vanessa J. Thompson & Dianne J. Bray, Craterocephalus stercusmuscarum in Fishes of Australia, accessed 01 Dec 2023,

Flyspecked Hardyhead, Craterocephalus stercusmuscarum (Günther 1867)

More Info


Known only from the Roper River, Northern Territory to the Dee River, Queensland. The Flyspecked Hardyhead forms shoals in still or slow moving sections of tropical rivers, small streams, lakes, ponds and reservoirs and fast-flowing creeks. Usually found in shallow water with sandy, gravel or muddy bottoms and aquatic vegetation.


Meristic features: Dorsal fin D1 IV-VII; D2 I, 5-10; Anal fin I, 7-10; Pectoral fin 12-16; Vertebrae 35-38; Gill rakers on lower branch of 1st arch 9-13.

Body laterally compressed, moderately slender, relatively elongate; mouth small, protrusible, oblique, with gape restricted by fusion of lips; rear edge of jaw does not reach back to eye; teeth in several rows in both jaws minute; gill rakers in first lower gill arch short and tubercular, less than half diameter of pupil; large speci-mens often with shallow interorbital trough and with head sloping obliquely towards snout; lateral line absent.

Body scales relatively large, dorsoventrally oval, with circuli complete and concentric; vertical scale count 32-35; horizontal scale count 6.5-7.5; preopercle and opercle with scales; head scales large and irregularly shaped.

No produced fin-spines; two separate dorsal fins; origin of first dorsal behind origin of ventral fin; origin of second dorsal fin above origin of anal fin; pectoral fin inserted forward of ventral fin; caudal fin moderately forked with rounded tips.


To 7.8 cm SL, commonly 5-6 cm.


Colour variable, generally green-grey dorsally, lower sides and ventral surface silvery; dark stripe from snout, across eye becoming black, gold or silvery and continuing to base of caudal fin; dorsal surface of head often black; body scales stippled on edges; base of each scale with a dark spot forming a series of longitudinal parallel rows along sides. Males with bright yellow or gold ventral surface during breeding season.


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


Spawns from October to February, and females deposit eggs onto aquatic plants during this time. The eEggs are relatively large, transparent and demersal, with filamentous adhesive strands, and measure approximately 1.3-1.7 mm in diameter. The larvae hatch after at 4.8-6.4mm SL after 13 days at 25-27°C.


Although not commonly kept the Flyspecked Hardyhead can be kept in an aquarium, and has been bred in captivity.


Colour may vary with locality and time.

Similar Species

Most similar to Craterocephalus fulvus which was originally thought to be a subspecies of C. stercusmuscarumC. fulvus lacks the spotted pattern, and has more vertebrae (35-38 versus 31-36). C.  stercusmuscarum also resembles C. lentiginosus but differs in fin ray and scale counts.


Craterocephalus is from the Greek, cratero meaning 'strong' or 'sturdy', and cephalus meaning 'head'. The specific name stercusmuscarum is from  the Latin stercus meaning 'dung' and muscari meaning 'of a fly', for the dark speckles on the sides.

Species Citation

Atherina stercusmuscarum Günther, 1867, Ann. Mag. Nat. Hist. (3)20(8): 64. Type locality: Cape York, QLD.


Vanessa J. Thompson & Dianne J. Bray

Flyspecked Hardyhead, Craterocephalus stercusmuscarum (Günther 1867)


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

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Günther, A. (1867). Additions to the knowledge of Australian reptiles and fishes. Ann. Mag. Nat. Hist. (3)20(8): 45–68

Ivantsoff, W. (1978). Taxonomic and systematic review of the Australian fish species of the family Atherinidae with references to related species of the Old World. Unpubl. Ph.D. Thesis Sydney : Macquarie Univ. 701 pp. 118 figs

Larson, H.K. & Martin, K.C. (1990). Freshwater Fishes of the Northern Territory. Northern Territory Museum of Arts and Sciences Handbook Series Number 1.  Darwin : Northern Territory Museum of Arts and Sciences 102 pp.

Leggett, R. & Merrick, J.R. (1987). Australian Native Fishes for Aquariums.  Artarmon : J.R. Merrick Publications 241 pp.

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

Pusey B., Kennard M. & Arthington A. (2004) Freshwater fishes of north-eastern Australia. CSIRO publishing, Collingwood, Victoria 684 pp

Quick Facts

CAAB Code:37246029

Fishing:Aquarium fish


Max Size:7.8 cm


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Species Maps

CAAB distribution map