R. Wager and P. Jackson
Environment Australia, June 1993
ISBN 0 6421 6818 0
Species recovery outline: Australian Grayling, Cucumber Mullet, Cucumber Herring
Scientific name: Prototroctes maraena
English names: Australian Grayling, Cucumber Mullet, Cucumber Herring
Species taxonomic status: Formally described by Gunther, 1864.
Species survival status: Widespread reduction in distribution due to habitat modification and destruction.
- Action plan status: Vulnerable.
- Australian Society for Fish Biology status: Potentially Threatened.
- Proposed new IUCN criteria status: Vulnerable (habitat alteration).
Former distribution: Widespread from the Grose River west of Sydney throughout New South Wales, Victoria and eastern South Australia. Also occurred throughout Tasmania and on King Island in Bass Strait.
Current distribution: Patchily distributed throughout the former range. Often only captured in small numbers (less than 10). Larger populations apparently restricted to a few rivers (eg Tambo River in Victoria).
Habitat: Australian Grayling is a diadromous species. The larvae are thought to be swept to sea and then return to fresh water (as whitebait) after four to six months. Freshwater habitats include large and small coastal streams and rivers. It is a mid-water species but it is unknown whether it has a preference for structural habitat.
Reasons for decline:
- Dams, weirs and culverts prevent dispersal, diadromous migrations, and recolonisation of previous habitat. Recently populations have been found immediately downstream of barriers in the Barwon and Yarra Rivers in Victoria.
- River regulation with loss of dry weather stream flow and suppression of minor flooding.
- Loss of riparian vegetation.
- Extensive stream siltation from accelerated catchment erosion due to agriculture and forestry practices.
- Stream channel damage from sand and gravel extraction.
- Alteration, particularly through siltation, of stream macro-invertebrate communities that provide food.
- Possible predation by Salmonids (eg brown trout) on the whitebait stage of the life cycle.
Conservation reserves on which species occurs: As this species is migratory and passes through large sections of unprotected rivers, and because riverine habitat is dependent on processes occurring throughout the catchment, National Parks probably offer little protection.
- Victoria – Five rivers in which grayling occur flow through National Parks:
- Snowy River National Park (however, the Snowy River has reduced and highly regulated flow);
- Wilsons Promontory National Park (one specimen only);
- Otway National Park;
- Croajingolong National Park;
- Aire River has recently been listed as a Heritage river.
- South-West National Park.
- New South Wales:
- Morton National Park.
Other public lands on which species occurs:
- Land controlled by the Colac and Geelong Waterboards, and the Lorne Foreshore Committee.
- Lorne-Anglesea State Park.
Other land on which species occurs: Private land.
Is knowledge about species adequate for objectives and actions to be defined accurately? (If not provide list of additional studies required): No.
- The general biology including habitat requirements of various life history stages (especially instream flow rates), possible migrations, spawning locations, reproductive biology, and recruitment processes need to be investigated.
- The most important river systems for recruitment need to be identified. It is suspected that only a few rivers may act as sources of larvae for the total population. This would require an investigation of genetic diversity.
- The current knowledge of role and mode of threatening processes is inadequate.
- Protect existing major populations and their habitats, especially those populations from which recruitment is greatest.
- Ensure free passage between estuaries and freshwater habitats.
Management actions already initiated:
- In New South Wales inter-departmental liaison with Water Resources, Public Works, Local Government, etc to manage habitat more effectively.
- Ban on taking of Australian Grayling in New South Wales in force.
- Research and management to maintain free passage for fish in streams.
- Planned survey of the status of New South Wales populations.
- Listed under Schedule Two of the Flora and Fauna Guarantee Act in Victoria.
Management actions required:
- Declaration of additional conservation reserves: No.
- Habitat management: Yes. Ensure adult fish have access to freshwater habitats.
- Feral animal control: Yes.
- Restrict stocking of salmonids into known habitats.
- Control salmonid populations in known habitats.
- Translocation or re-establishment of populations: Not required. Marine larval stages probably disperse widely and have the ability to recolonise suitable habitat.
- Captive breeding: Not required, although artificial fertilisation and hatching was achieved by Saville-Kent in the 1890s.
- Other: Yes.
- Research into basic biology required.
- Identification of breeding populations.
Organisations responsible for conservation of species:
- Victorian Department of Conservation and Natural Resources.
- Department of Agriculture and Fisheries, New South Wales.
- Inland Fisheries Commission, Tasmania.
Other organisations or individuals involved: None.
Can recovery plan be carried out with existing resources?: No.
The conservation of Australian Grayling requires action over a broad range of topics, some of which are being addressed by state authorities, eg fish passage. However there are key aspects of the biology of Australian Grayling which require a well directed research project to elucidate. In the past research on Australian Grayling has been undertaken on an ad hoc basis with limited resources. The resolution of distribution and genetic diversity would require a major co-operative project between fisheries authorities in New South Wales, Victoria and Tasmania.
- Determination of basic biology could be achieved from one state. One biologist and one technician would be required for three years – $220 500. Operating costs of $30 000 would be required each year.
- Distribution and determination of genetic diversity would require one biologist and one technician for two years – $147 000 plus operating costs – $30 000 per year.
Total: $517 500
- A congeneric species in New Zealand, Prototroctes oxyrhynchus, became extinct in a short period early this century.