Australian Grayling, Prototroctes maraena Günther 1864

Other Names: Cucumber Fish, Cucumber Herring, Cucumber Mullet, Cucumberfish, Cucumber-fish, Grayling, Yarra Herring

Australian Grayling, Prototroctes maraena. Source: Tarmo A. Raadik. License: All rights reserved

Silvery freshwater fishes with a small adipose fin on the rear of the back, a keel along the belly, no lateral line and a horny sheath around the lower jaw. 
Adult Australian Grayling inhabit freshwater rivers and streams. During autumn, they undertake large migrations to spawn in the lower reaches of rivers. The newly hatched larvae are swept out to sea and migrate back to estuaries after about 6 months. The species has a distinct cucumbery smell.

Cite this page as:
Gomon, M.F. & Bray, D.J. 2017, Prototroctes maraena in Fishes of Australia, accessed 26 Mar 2019,

Australian Grayling, Prototroctes maraena Günther 1864

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Endemic to coastal drainages of southeastern Australia, from the Shoalhaven River, New South Wales, westward to the eastern part of South Australia, and widespread in coastal Tasmania, including King Island in Bass Strait. Historic records show that Australian Grayling were once found as far north as the Grose River near Sydney. 

Adults prefer moderate to fast-flowing water in rivers and streams, usually in cool clear waters below altitudes of 200 m, although they have been recorded above 1000 m in Victoria. They often occur in pools with gravelly substrates, and may form large schools, especially before spawning.

The Australian Grayling is diadromous, migrating between rivers and coastal waters during its life cycle. The species therefore relies on having free access to a range of freshwater, estuarine and marine coastal habitats.


Dorsal fin 9-13; Anal fin 16-20; Pectoral fin 12-14; Pelvic fin 6; Vertebrae 62-65.

Body long and slender, compressed; head small, conical with bluntly rounded snout; eye of moderate size; mouth slightly oblique, small; gape extending back to beneath eye; lower jaw shorter than upper jaw, tapering to a fine point; gill rakers on first arch 20-26; teeth in upper jaw blunt in a comb-like row; weak abdominal keel present in front of anus. Scales thin, cycloid of moderate size, 68-86 in lateral series; lateral line absent. Dorsal fin in about middle of back, behind ventral fin; small adipose fin present behind dorsal; ventral fins on middle of belly, small, rounded; caudal fin forked; anal fin beneath space between dorsal and adipose fin; pectoral fins well forward, low, small, triangular.


Maximum size to 33 cm TL but commonly to 17-19 cm TL.


Dusky brown to greenish-brown above, greenish to bronze midlaterally and silvery-white to yellowish below. Sometimes has a steely-blue mid-lateral band and dark spot on the caudal fin base. Fins greyish-white.


Australian Grayling are omnivores, feeding mainly on algae, and also on a variety of small aquatic invertebrates, including microcrustaceans, insects and their larvae. They have highly specialised dentition that allows them to comb filamentous algae growing on rocks, and a long specialised gut to help digest algae.


The Australian Grayling is an amphidromous species. Adults inhabit freshwater rivers and streams, and undertake spawning migrations to the lower reaches of rivers between February and May - usually coinciding with increased river flows. The species is highly fecund, and females spawn on average 47000 eggs in autumn (April-May) following high water flows and a drop in temperature.

The demersal eggs sink to the bottom downstream of where they are spawned. Larvae hatch at 6-7 mm TL after 10-20 days, and are carried downstream into estuaries and out to sea. They spend 5-6 months at sea before migrating back to freshwaters as part of the spring 'whitebait run'.


Once popular with recreational anglers, but now protected under the EPBC Act and protected in New South Wales. Heavy penalties apply for taking or possessing them.


IUCN Red List: Near threatened.

EPBC Act 1999: Vulnerable

NSW Fisheries Management Act 1994: Protected

VIC Flora & Fauna Guarantee Act 1988: Protected. Taking or attempting to take, including catch and release, is prohibited.

Populations of Australian Grayling have declined due to a range of factors including habitat degradation, barriers to movement, competition with introduced species, including Eastern Gambusia (Gambusia holbrooki) and trout species, climae change and fishing. The species is now the focus of a number of conservation measures.


Grayling often form aggregations below barriers to upstream movement such as weirs and waterfalls. Exudes a cucumber-like smell when freshly caught.

Researchers have found that adult Australian Grayling in the Thomson River, Victoria, undertake downstream spawning migrations (up to 140 km) to the lower river to coincide with environmental flow releases (Amtstaetter et al. 2015).

Species Citation

Prototroctes maraena Günther 1864, Cat. fishes Brit. Mus.5: 382. Type locality: Southern Australia.


Gomon, M.F. & Bray, D.J. 2017

Australian Grayling, Prototroctes maraena Günther 1864


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Quick Facts

CAAB Code:37103001

Biology:Migratory with marine larvae

Conservation:EPBC Act Vulnerable; IUCN Near Threatened

Habitat:Freshwater, estuarine, marine larvae

Max Size:33 cm TL

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