Craterocephalus dalhousiensis Ivantsoff & Glover 1974
Dalhousie hardyhead

ATHERINIDAE, Haryheads or silversides



image 28KK jpeg.60mm (2.4in) TL. Ross Felix photo.


Size

The largest recorded is 78mm (3in) SL. They are commonly found up to 50mm (2in).

Conservation Status

It is listed as Vulnerable by the Australian Society for Fish Biology.

Distribution & Abundance

image

Restricted to approximately seven springs at Dalhousie Springs (shown by the black dot). They are usually very abundant.

Habitat & Ecology

Dalhousie hardyheads occur in the wild at temperatures from 20C to 40C (68 to 104F) and make very brief excursions into water of 41.8C (107F). This is the highest recorded voluntary temperature tolerance of any Australian fish and one of the hottest voluntary temperatures that fish have been recorded at anywhere in the world!. They are generally found in the pools and channels in the spring outflows. The minimum dissolved oxygen tolerated is 0.5 mg O2/L. Their diet consists mostly of green filamentous algae but also includes ciliates, ostracods, insects, hydrobiid snails, detritus, and worms (Glover 1989).

Reproduction

Dalhousie hardyhead is the only member of the genus known to be morphologically sexually dimorphic. Virtually nothing is known of reproduction in the wild. In aquaria they are easily spawned. They probably lay in excess of around 20 eggs a day when temperatures are maintained over 24C (75F). Their upper spawning temperature is yet to be investigated. They readily spawn on mops, most spawning activity takes place in the morning. They also readily eat their eggs. At 28C (83F) eggs take about 7 days to hatch. Fry are about 5mm (0.2in) TL at hatching. Fry are usually first fed vinegar eels until they are large enough to ingest baby brine shrimp. Fry typically grow slowly in aquaria. It is not known whether they reproduce throughout the year or seasonally under natural conditions.

Threats

The greatest threat is their restricted range. At Dalhousie Springs, the dominant threat is the potential introduction of exotic species, however no introductions have been recorded yet.

Conservation Action

Dalhousie Springs is completely enclosed within Witjira National Park. There is also ongoing population monitoring being conducted by Bryan Pierce from the South Australian Research and Development Institute.

Conservation Recommendations

Continue regular population monitoring.

Important References

Glover, C. J. M. 1989. Fishes. In, Natural History of Dalhousie Springs. Eds. Zeidler, W. & Ponder, W. F. South Australian Museum, Adelaide. pp 89-112.

Ivantsoff, W. I. & Glover, C. J. M. 1974. Craterocephalus dalhousiensis n.sp., a sexually dimorphic freshwater teleost (Atherinidae) from South Australia. Australian Zoologist. 18: 88-98.


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This file was last modified:  18 March 2003