Melanotaenia maccullochi [Harvey Ck, Russell River] - photo© Gunther Schmida

Melanotaenia maccullochi


Ogilby, 1915
McCulloch's Rainbowfish

Species Summary
Melanotaenia maccullochi were initially collected in 1915 from the Barron River, inland from Cairns, north Queensland, and described by J.D. Ogilby as Melanotaenia maccullochi. They were named after the ichthyologist, Allan R. McCulloch (1885-1925). It is therefore, according to recognised nomenclature rules, pronounced McCulloch - eye, not mac - cul - lo'kee.

Melanotaenia maccullochi is another rainbowfish species that varies across its wide distributional range. Several geographically isolated populations are found in northern Queensland. Several distinct colour forms are known, which show marked variation in the intensity of the dark body stripes and markings on the dorsal and anal fins as well as differences in the colour of the 'spawning' stripe on the nape of males. This coloured nape is flashed on and off during spawning activities and may be white, yellow, orange or red.

Differences between the various populations are considerable and I would not be surprised to see them separated into distinct species at some later date. Therefore, for the serious rainbowfish breeder, it is very important to maintain each distinct population separately in captivity.

Male specimens of the variety found between Cairns and Innisfail are easily recognised by the silvery-white or yellowish body colour and 6-8 reddish-brown stripes on sides. The dorsal and anal fins are orange-red with a lower black margin running along the body line. The caudal fin has a fan of orange-red colouration. Females are much less colourful, though some do show a hint of the male's coloration. Females of this variety tend to grow larger and have deeper bodies than males.

The variety found in the drainage division of the Jardine River are characterised by a series of fine black stripes on the sides, with black submarginal bands and white to yellowish margins on the dorsal and anal fins. Females generally have the stripes less defined. They are also a lot smaller than the other varieties, both in length and body depth. The population from the latter area is similar to those that occur in the southwestern lowlands of Papua New Guinea. The varieties found north of Cairns but south of the Jardine River are intermediate. However, the stripe pattern is plain and they do not show the orange-red colouration. An unusual blue coloured form has been collected in the Hope Vale region; a remote region situated 46 kilometres north of Cooktown

Melanotaenia maccullochi [Burton Ck, Finniss River] - photo© Gunther Schmida

In 1988 a new colour variety was collected from a small shallow stream known as Burton Creek. Burton Creek is a spring-fed tributary in the Finniss River catchment. This variety has clear to yellowish dorsal and anal fins with bluish edges above a black sub-marginal band. The body colour is silver to yellowish with a dark mid-lateral stripe and grows to a much smaller size than the other varieties. More recently (2007) another population was found in Tolmer Creek, a tributary of the Reynolds River in the Northern Territory. These are similar to the Burton Creek population.


Distribution Map



Distribution & Habitat
Melanotaenia maccullochi occur as a number of isolated populations in southern New Guinea and northern Australia. In Australia, several isolated populations are known to exist in Queensland and the Northern Territory. The distribution in Queensland includes the coastal plains between Cairns and Innisfail. In this region they have been collected from the Barron, Mulgrave (Behana Creek), Russell (Harvey Creek), Johnstone and Moresby Rivers, Maria Creek, Hull River and the Murray/Tully Rivers. They are also found from the Daintree River north through Cooktown to the McIvor River and streams in the Hope Vale region (Black Creek). Another area where they are found is Cape York Peninsula, primarily in the Jardine River and its tributaries. They also occur at Cape Flattery and the Olive River and probably occur elsewhere along the east coast of Cape York Peninsula that has suitable habitat. Small isolated populations have also been found in two locations in the Northern Territory. The known New Guinean distribution encompasses the lower and middle sections of the Fly River westward to the Bensbach River.

Wild populations are still abundant in New Guinea and Cape York Peninsula, but the more southerly populations along the Queensland coast have declined due to habitat destruction. The extensive development of coastal floodplains has contributed to the demise of this species. It is now confined to a relatively few widely scattered locations and has long been absent in the Barron River, the site of its first capture. The Murray River and its floodplain lagoons represent the remaining habitat of the Cairns colour form.

Melanotaenia maccullochi are generally found in lowland swamps and small streams, usually in clear, moderately flowing streams, grassy wetland swamps and tannic stained ponds in sandy coastal floodplains. Often with ample cover in the form of log debris or aquatic vegetation. The water in these natural habitats is usually very soft and often tannin stained. A temperature range of 19-32°C and pH values of 5.5-7.0 have been recorded in their natural habitats.

Melanotaenia maccullochi [Hope Vale] - photo© Gunther Schmida

Biology
Very little is known about the biology of this species in their natural environment. Most information is mainly based on aquarium observations. They may reach a maximum size of 6 cm, but usually less than 4 cm. Melanotaenia maccullochi are most likely aseasonal spawners, breeding continuously at intervals throughout the year. However, a peak in reproductive activity is usually during the early-wet season, from October to December. The breeding season must coincide with the conditions that offer the greatest amount of protection for the eggs, and food and shelter for the newly hatched young. Strong sexual dimorphism is present in the species with males typically being brighter in colouration. Before spawning, a bright spawning stripe is evident in the males. It runs from the tip of the mouth to the first dorsal fin on the dorsal surface of the fish. Females produce between 20-30 eggs each day for several days. Eggs are attached by adhesive threads or tendrils to a range of submerged physical structures, including gravel substrates, woody debris, root masses, aquatic vegetation and submerged marginal (riparian) vegetation, which hide them from predators. The eggs are fairly large (1.5 ± 0.5 mm in diameter), and light amber to yellowish in colour. However, the eggs are subject to desiccation if the water level drops or to dispersal if there is a flood. It will take around 8-9 days at 28°C for the first young to appear. Larvae achieve a length of around 12 mm by 60 days and 2.5-3.0 cm in five months, when they become sexually mature. Melanotaenia maccullochi is an opportunistic omnivore. The main food items are aquatic insects, algae and terrestrial insects. Their diet varies in relation to the habitat they occupy.


Remarks
Melanotaenia maccullochi is one of the smaller species of rainbowfishes and have been a popular aquarium fish for many years. They were first introduced to the international aquarium hobby in 1934, when Amandus Rudel, a founding member of the Aquarium & Terrarium Society of Queensland, sent 12 specimens, collected by him near Cairns, to Fritz Mayer in Hamburg, Germany. Four arrived alive and developed into 2 pairs. They were one of the most popular aquarium fish from Australia. In the German aquarium magazine "Wochenschrift für Aquarien und Terrarienkunde" in May 1935, Fritz Mayer gave the first account of their breeding, which was translated and elaborated upon by F. H. Stoye in Innes' "The Aquarium" in December 1936.

Through my correspondence with friends in all parts of the world, I have been able to instigate new imports. In this way I became acquainted with Mr. A. Rudel of Brisbane, Australia, who notified me December, 1934, that he was sending me twelve Melanotaenia mccullochi, collected by him near Cairns, northeastern Australia. Four arrived alive and developed into 2 pairs. ~ Fritz Mayer, Hamburg (1935).

Melanotaenia maccullochi [Skull Creek, Jardine River Catchment] - photo© Gunther Schmida


Literature
Allen G.R. (1989) Freshwater fishes of Australia. T.F.H. Publications, Inc., Neptune City, New Jersey.

Allen G.R., S.H. Midgley and M. Allen (2002) Field guide to the freshwater fishes of Australia. Western Australian Museum, Perth, Western Australia.

Ogilby J.D. (1915) On some new or little-known Australian fishes. Memoirs of the Queensland Museum 3: 117-129, Pls. 29-30.

Adrian R. Tappin
Updated May, 2013


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