Melanotaenia utcheensis (Utchee Creek) - photo© Gunther Schmida

Melanotaenia utcheensis

Species Summary
Melanotaenia utcheensis has an overall body colouration of silvery-white, often with a faded orange colour near the midline. The head and gill region is silver to pink and fish often have a reddish cheek patch. Scales have a bluish iridescence, especially on the upper half of the body. There is an orange stripe between each horizontal scale row. The mid-lateral band starts dark at the tail and fades forwards, tending towards blue in males and black in females. Anal, dorsal, pelvic and caudal fins range from translucent to deep red, being most strongly coloured in males. The anal, second dorsal and pelvic fins often have black margins, especially in males. Pectoral fins are translucent. Males tend to be more brightly coloured than females. Males are also deeper bodied and have longer pelvic, dorsal and anal fins.

Melanotaenia utcheensis belongs to an old rainbowfish lineage whose closest relative is M. duboulayi. The observation of various morphs of M. utcheensis from different streams and stream reaches indicates that populations may have been isolated from each other for some time. Melanotaenia utcheensis is morphologically distinct from the broadly sympatric M. eachamensis and M. splendida. In particular, M. utcheensis has more first dorsal spines and fewer vertical scale rows and anal rays than M. splendida, and fewer soft second dorsal rays and more pectoral rays than M. eachamensis. Melanotaenia utcheensis is also generally smaller than either M. splendida or M. eachamensis and intermediate between them in eye diameter, predorsal length, head depth and body depth.

Melanotaenia utcheensis (Berner Creek) - photo© Gunther Schmida

Distribution & Habitat
Melanotaenia utcheensis have been collected from a number of streams in the North and South Johnstone River catchments in north Queensland. They are a highly specialised species restricted to a small geographical area and a unique habitat. They have been found in sites with moderate to high water flow over cobbles and boulders. The headwaters of the Johnstone River system rise in the Atherton Tablelands. The north branch of the river system rises below Merivale, flows over the Malanda Falls and through the town of Malanda and then flows generally south by east, around the Francis Range and over the Jones Falls, before flowing east, covering a distance of about 114 kilometres. The south branch of the river system rises below Mount Father Clancy and generally flows east over Binda Falls, through the settlement of South Johnstone, before flowing north, covering a distance of about 88 kilometres. The two rivers reach their confluence to form the Johnstone River east of the town of Innisfail, and just 5 kilometres west of the river mouth. The main river then flows east, north of the Moresby Range National Park, and empties into the sea.

Melanotaenia utcheensis (Bora Creek) - photo© Gunther Schmida

Biology & Ecology
Not a lot is known about the biology or ecology of M. utcheensis in their natural environment. Most information is mainly based on aquarium observations. Under aquarium conditions, pre-spawning behaviour usually occurs in the morning and may continue for up to an hour before spawning takes place. During this period the colours in both sexes become more intense, but to a lesser extent in the female. Spawned eggs, which range in size from 0.70 to 0.90 mm in diameter, are adhesive, negatively buoyant in freshwater and are usually clear to light amber in colour. The eggs hatch after an incubation period of four to nine days depending on temperature. Temperature is one of the major factors that influences the embryonic period for rainbowfishes. Average embryonic period is about 5-6 days at 28°C (+/- 2°C). The average larval length of M. utcheensis at hatching ranges from 2 to 4 mm, which is similar to other rainbowfish species.

Melanotaenia utcheensis (Miskin Creek) - photo© Gunther Schmida

Literature
Flint N. (2005) Sublethal effects of diel fluctuations in dissolved oxygen saturation on freshwater fishes from tropical Queensland. PhD thesis, James Cook University.

McGuigan K.L., D. Zhu, G.R. Allen and C. Moritz (2000). Phylogenetic relationships and historical biogeography of melanotaeniid fishes in Australia and New Guinea. Marine and Freshwater Research 51: 713-723.

McGuigan K.L. (2001). An addition to the rainbowfish (Melanotaeniidae) fauna of north Queensland. Memoirs of the Queensland Museum 46: 647-655.

Adrian R. Tappin
Updated July, 2017