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Freshwater Fish of Victoria: Blackfish | AG0052 |
Fisheries Victoria, Melbourne
Updated: March 2007
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Common Name:
River blackfish (Illustrated)
Other Name:
Blackfish, slippery, slimy, marble cod, greasy
Family:
Gadopsidae
Scientific Name:
Gadopsis marmoratus Richardson, 1848
Status:
Native | |
Description
Long rounded body. Very small scales. Long, low dorsal and anal fins, the dorsal fin appearing to be joined with the rounded tail fin, but actually separate. The pelvic fins are located on the underside of the body below the gills, and consist of one or two rays. Large head with rounded snout, low placed mouth which reaches back to the front edge of the eye. Lower jaw is shorter than the upper. Moderate sized eye located high on the head. Body invariably has a heavy coating of slime. Dorsal fin has 6-13 spines (as distinct from the Two-spined blackfish, G Bispinosus described later).
Colouring very variable, mottled yellowish, brownish-green or grey, but also dark brown to a light bluish or greenish-brown with blotches on the upper body, with many irregular darker blotches. Lower body may be light blue, yellow or purple. Fins olive-brown to black.
Distribution
Widespread in Victoria, both north and south of the Great Dividing Range. Common throughout most of its range.
Habitat
Although it is found in a variety of habitats, it is most common in cooler, flowing streams where there is plenty of rock cover with abundant snags, fallen timber and debris, and gravel bottom. A bottom fish. Also occurs in slow-flowing lowland rivers, coastal and inland lakes, and reservoirs.
Brief Biology
Can grow to 60 cm and 5 kg, but is usually less than 30 cm and 450g. The number of eggs per female depends on body length. Relatively few eggs are laid, with a female of 30 cm laying about 500 eggs. Spawning occurs in spring and early summer when water temperatures reach about 16°C.
The strongly adhesive eggs are laid in hollow logs and rock cavities and have been found inside pieces of discarded PVC piping. Observation suggest that the male guards the eggs. Young fish hatch about a fortnight later, and at about 5 weeks old are actively swimming and seeking food. Con¬fined as they are to the bottom and spending much of their time in the leaf litter and debris, predation on the young by crustaceans and dragonfly nymphs can be heavy.
The species will breed in streams and lakes, and has been known to breed in farm dams where suitable habitat is available. A carnivorous fish, eating a wide variety of aquatic insects, molluscs, crustaceans, smaller fishes and terrestrial invertebrates that fall into the water. Diet varies with locality and abundance of available food.
Other Notes
River blackfish (and the more recently described Two-spined River blackfish) are unique to Australia. An excellent angling species with sweet tasting flesh. Furtive and secretive, they move mainly at night, late evening and early morning in search of food.
Abundance has been affected in some areas due to the im¬pact of man, including increased siltation of streams due to changed land usage, clearing of debris from streams (de-snagging), changed stream flow regimes resulting from the construction of water storages and in some cases competition from introduced fish such as trout.
Common Name:
Two-spined Blackfish
Family:
Gadopsidae
Scientific Name:
Gadopsis bispinosus Sanger, 1984
Status:
Native
Description
Generally as for River blackfish, G. marmoratus described earlier, with the primary distinction being two, or rarely one or three spines in the dorsal fin. Often spotted (leopard type) on the body, with white fin margins of the dorsal and anal fins.
Distribution
Appears to be confined to streams in north-eastern, east from King Parrot Creek. Populations of River blackfish exist in the Grampians area (western Victoria) which are very similar to Two-spined blackfish possessing down to 3 spines in the dorsal fin.
Habitat
Cool, flowing streams with gravel substrate and good instream vegetation, fallen timber, debris and boulders, at higher altitudes.
Brief Biology
Similar to G. marmoratus described earlier.
Other Notes
Only recently identified as a distinct species. Both species of blackfish may be found living together in the same section of stream, though River blackfish are generally in the lower elevation, slower-flowing warmer streams.
Regulations
(both species) Details of recreational fishing licence requirements and regulations for the taking of river blackfish are available in the Victorian Recreational Fishing Guide, available free of charge at DPI offices and Recreataional Fishing Licence sales outlets.
Further Reading
Freshwater Fish of Victoria is a series of brief information material on the native and introduced freshwater fish of Victoria's inland waters. Further, detailed reading on river blackfish is contained in:
- A Guide to the Freshwater Fish of Victoria, Phillip Cadwallader & Gary Backhouse, Department of Conservation and Environment
- Australian Freshwater Fishes, John R. Merrick & Gunther E. Schmida
- Biological Information for Management of Native Freshwater Fish in Victoria, J D Koehn, W G O'Connor
Acknowledgements
This Information Note was developed by Charles Barnham PSM, with the assistance of Gary Backhouse, Phillip Cadwallader and Tarmo Raadik. The previous version was published in February 1998.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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