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Prototroctes maraena (Family Retropinnidae)

Australian Grayling

Distribution:

The Australian Grayling is now confined to streams draining to the coast in south-eastern Australia, from central New South Wales southward to the Glenelg River in western Victoria, and also in Tasmania. They range from sea level up to approximately 800 m (NSW, VIC, TAS).

Features:

The Australian Grayling is a smallish freshwater fish that grows to over 300 mm in length, but usually to 200 mm. This species has a slender body and small head, large eyes and a blunt snout. A single dorsal fin is set back from the middle of the body, though forward of the anal fin, and there is a small adipose fin just before the tail. Scales are small, and the body is silvery on the sides, to olive-grey on the back and whitish on the belly. One distinguishing characteristic of this species, also found in Australian Smelt (Retropinna semoni), is a strong cucumber smell, which is emitted by the fish when caught.

Ecology/Way of Life:

The Australian Grayling is usually found in clear, gravelly streams, often shoaling in pools or found in fast flowing rapids or runs, at low elevations, and in upland mountain streams. Spawning occurs in low elevation freshwater reaches, the larvae are thought to be washed downstream to the estuary or the sea, and then migrate back upstream into freshwater to complete their life cycle. Spawning occurs during late summer or autumn, and is associated with a drop in water temperature, and may also be associated with a rise in river flow. The female sheds between 25,000 and 68,000 small eggs into the water column and it is thought that after fertilisation, the small eggs settle amongst gravel in the streambed. Juvenile fish return to freshwater approximately six months later, and males reach maturity after 1 year of age, and females after 2 years. Most fish die between the ages of 2 and 3 years, with very few fish reaching four years of age. Australian Grayling are considered to be a microphagic omnivore, feeding on small macroinvertebrates and algae.

Interaction with Humans/Threats:

This species is one of Australia's most threatened fishes, though the threats to its survival are poorly known. Australian Grayling were very widespread and abundant during the early days of settlement in Australia, but soon after dramatically declined and almost disappeared. They are still spasmodically found in each of the states listed above, but generally in low numbers. It is thought that a disease, potentially introduced into Australia with the introduction of Brown Trout (Salmo trutta) in the mid 1800's caused their initial dramatic decline, and impoundments preventing migration and recolonization, water regulation, and predation by introduced Brown Trout (Salmo trutta) on newly recruiting juveniles are currently implicated in keeping population abundances low.

Other Comments:

Prototroctes maraena was named by Günther in 1864. The name is based on Greek, Proto or prot meaning first or primary, troct meaning a nibbler or gnawer and maraena, possibly named after the salmonid Coregonus maraena, as fish of the genus Prototroctes have the appearance of northern hemisphere Coregonus.

Further Reading:

Allen, G. R., Midgley, S. H. & Allen, M. (2002). Field Guide to the Freshwater Fishes of Australia. Western Australian Museum. Perth. 394pp.

Berra, T. M. (1982). Life history of the Australian Grayling, Prototroctes maraena (Salmoniformes: Prototroctidae) in the Tambo River, Victoria. Copeia 1982: 795–805.

Jackson, P. D. & Koehn, J. D. (1988). A review of biological information, distribution and status of the Australian grayling Prototroctes maraena Gunther in Victoria. Arthur Rylah Institute for Environmental Research Technical Report Series No. 52. Department of Conservation, Forests and Lands, Melbourne.

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

McDowall, R. M. (1976). Fishes of the family Prototroctidae (Salmoniformes). Australian Journal of Marine and Freshwater Research 27: 641–659.

McDowall, R. M. (ed). 1996. Freshwater Fishes of South–eastern Australia. Reed, Sydney. 2nd edition. 247pp.

Acknowledgments:

Text: Tarmo A. Raadik. Distribution map: Peter J. Unmack. Photographer: Gunther Schmida.

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