Bighead Threefin, Trianectes bucephalus McCulloch & Waite 1918

Other Names: Big-head Threefin, Bullhead Triplefin, Ox-headed Triplefin, Verco's Triplefin

A Bighead Threefin, Trianectes bucephalus, at Portsea, Port Phillip, Victoria, April 2006. Source: ronigreer / License: CC By Attribution-NonCommercial

A well camouflaged mottled green, brown or purple threefin with dark blotches along the back and upper sides, often a yellow or purple head, a mottled black first dorsal fin, diagonal lines on the second and third dorsal fins, and spotted pectoral fins.

Cite this page as:
Bray, D.J. 2021, Trianectes bucephalus in Fishes of Australia, accessed 20 Jul 2024,

Bighead Threefin, Trianectes bucephalus McCulloch & Waite 1918

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Endemic to southern Australia, from Wilsons Promontory, Victoria, to Eagle Bay, Western Australia, and northern and eastern Tasmania. Inhabits shallow reefs and tidepools at depths to 5 m. The species is rarely seen as it is nocturnally active and often shelters under ledges and beneath small rocks during the day.


Dorsal fin III + XIV-XV + 11-12; Anal fin II, 21; Caudal fin 13; Pectoral fin 15-16; Pelvic fin I, 2; Lateral line scales (upper) 27-28.
Body of moderate length and depth (approx. 24% SL), almost cylindrical, slightly compressed. Head moderately large (approx. 35% SL), depressed and pointed; eyes large (approx. 33% HL); small, rounded fleshy tentacle above each eye; anterior nostril tubular with simple lobate tentacle; mouth large, reaching below posterior half of eyes, slightly oblique; teeth pointed, set in bands, outer rows widely spaced and enlarged.  
Scales ctenoid, large, covering body, but not head and pectoral fin base; lateral line in two parts, upper section running from upper end of gill opening, following contour of back, to below third dorsal fin, lower section represented by posteriorly notched scales, only some with pores, originating below origin of upper section, curving downwards behind pectoral fin to midline of side, portion below upper section poorly developed and with very few notched scales, those below and behind upper section notched; pores on head large and numerous.  
Dorsal fin in three distinctly separate sections of similar height, first with much shorter base and slightly lower than second, first and second spinous, third with unbranched soft rays and base slightly shorter than that of second; anal fin with elongate base and uniform height; caudal fin rounded. Pectoral fins large, uppermost ray simple and short, other rays in upper half of fin branched to base, rays in lower half simple but strong, middle rays longest, reaching near end of second dorsal fin. Pelvic fins simple, jugular, inserted in advance of first dorsal fin origin. 


The specific name bucephalus is a Latinisation of the Greek bous (= ox) and kephale (= head), meaning ox-headed, in reference to the 'large naked' head of this species.

Species Citation

Trianectes bucephalus McCulloch & Waite  1918, Rec. S. Aust. Mus. (Adelaide) 1(1): 53, pl. 3(3). Type locality: Spencer Gulf, South Australia.


Bray, D.J. 2021


Atlas of Living Australia

Bighead Threefin, Trianectes bucephalus McCulloch & Waite 1918


Fricke, R. 1994. Tripterygiid fishes of Australia, New Zealand and the Southwest Pacific Ocean, with descriptions of 2 new genera and 16 species (Teleostei). Theses Zoologicae 24: 1-585 figs 1-130 

Gomon, M.F. 2008. Family Tripterygiidae. pp. 684-693 in Gomon, M.F., Bray, D.J. & Kuiter, R.H. (eds). Fishes of Australia's Southern Coast. Sydney : Reed New Holland 928 pp. 

Kuiter, R.H. 1993. Coastal Fishes of South-eastern Australia. Bathurst : Crawford House Press 437 pp. 

Kuiter, R.H. 1994. Families Blenniidae and Tripterygiidae. pp. 728-740 in Gomon, M.F., Glover, C.J.M. & Kuiter, R.H. (eds). The Fishes of Australia's South Coast. Adelaide : State Printer 992 pp. 810 figs. 

McCulloch, A.R. & Waite, E.R. 1918. Some new and little known fishes from South Australia. Records of the South Australian Museum (Adelaide) 1(1): 39-78 figs 26-31 pls 2-7 See ref at BHL

Thomson, J.M. 1978. A Field Guide to the Common Sea & Estuary Fishes of Non-tropical Australia. Sydney : Collins 144 pp. 

Whitley, G.P. 1931. New names for Australian fishes. The Australian Zoologist 6(4): 310-334 1 fig. pls 25-27

Williams, J. 2014. Trianectes bucephalus. The IUCN Red List of Threatened Species 2014: e.T178960A1552829. Downloaded on 15 February 2018.

Quick Facts

CAAB Code:37415027

Conservation:IUCN Least Concern

Depth:0-5 m

Habitat:Reef associated

Max Size:7 cm


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