Tropical Nightfish, Bloomfield Cod
The Tropical Nightfish is only known from the upper reaches of the Bloomfield River in northern Queensland (QLD).
Tropical Nightfish grow to approximately 200 mm. They are plainly coloured with an olive brown back and body, becoming lighter on the sides and belly. There is a slight mottling on the sides, sometimes forming indistinct stripes, and there are often a number of light splotches or dots on the rear half of the body. The fins are the same as the body colour and the paired fins may have white leading filaments. The Tropical Nightfish has a rounded caudal fin and a rounded snout. It is difficult to distinguish from juveniles of other percichthyids but its distribution is far removed from other species so that there should be no confusion.
Ecology/Way of Life:
The Tropical Nightfish lives in flowing areas amongst boulders and rocky outcrops with gravel substrates. They are mostly solitary and seem to patrol overlapping territories, chasing smaller individuals away. They eat shrimps and aquatic insects and probably also take small fishes. Little is known regarding their ecology and breeding biology.
Interaction with Humans/Threats:
The Tropical Nightfish was discovered in 1994. It has an extremely limited distribution in a largely undisturbed catchment within the wet tropics zone. Any development in the catchment could be potentially threatening. Introduction or translocation of angling species could also be potentially threatening as this species only occurs in parts of the Bloomfield River where species such as the Sooty Grunter (Hephaestus fuliginosus) are absent. It may become subject to over exploitation by the aquarium trade as it makes an interesting, if not very attractive, display. The phylogeny of this species and its anomalous distribution may be useful in interpreting past climatic changes of the Australasian region. This species may also be useful in the aquaculture industry in terms of investigating the hatchery breeding of other percichthyids.
Guyu wujelwujalensis was named by Pusey and Kennard in 2000. The species name wujalwujalensis is from Wujal wujal, a traditional name for the area in which it occurs.
Allen, G. R., Midgley, S. H. & Allen, M. (2002). Field Guide to the Freshwater Fishes of Australia. Western Australian Museum. Perth. 394pp.
Pussy, B.J. & M. J. Kennard, (1994). The freshwater fish fauna of the Wet Tropics Region of northern Queensland. Final report to the Wet Tropics Management Authority.
Text: Rob Wager & Peter J. Unmack. Distribution map: Peter J. Unmack. Photographer: Gunther Schmida.
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