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| Melanotaenia lacustris (male) - photo© Neil Armstrong |
Munro, 1964
Lake Kutubu Rainbowfish
Description
Depending on water conditions, captive environment and diet, Melanotaenia lacustris can display an array of different colours and patterns ranging from cobalt blue, steel blue, aquamarine through to lighter and darker shades of turquoise. When spawning the nape area changes to a bright orange or gold colouration.
Distribution
Found only in Lake Kutubu and the Soro River, which is the only outlet stream of the lake. The Soro River eventually flows into the Kikori River system. In late 1983 Gerald Allen, John Paska, and Barry Crockford collected around 40 live specimens. Only 4 fish (1 male and 3 females) survived the journey back to Australia and a week after arriving in Melbourne the only male became infected with hook worm and subsequently died. The aquarium hobby had to wait another 3 years before Heiko Bleher was able to collect further live specimens. He returned in 1988 together with Gerald Allen and once more was able to bring back live specimens. Water conditions recorded at the lake were a temperature range of 21 to 25°C and a pH of 8.5-9.0.
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| Melanotaenia lacustris (female) - photo© Neil Armstrong |
Habitat & Ecology
Lake Kutubu is a scenically beautiful crystal clear lake situated about 40 kilometres from Mendi, the main town of the Southern Highlands Province in central Papua New Guinea. Lake Kutubu was originally formed when debris and ash originating from a volcano, blocked a valley. It is the 2nd largest lake in PNG and its largest perched lake. Measuring approximately 19 km by 4 km at its widest point, it has a maximum depth of about 70 m. An exceptionally clear lake where, in contrast to most of PNG's inland waters. The Lake plays a significant role in the maintenance of biodiversity of the Kikori River basin and beyond. The lake's extraordinary level of fish endemicity (10 of the 14 fish species found within the Kikori drainage are endemic to the lake itself) exceeds that of any other lake in the entire New Guinea-Australian region. The Kikori drainage and the surrounding primary rainforest also support high levels of endemism and rare terrestrial fauna. Lake Kutubu provides the sole spawning, nursery and feeding grounds for the 10 species of endemic fish.
Melanotaenia lacustris may reach a maximum size of 12 cm, but usually less than 10 cm. Males are more brightly coloured, larger, and with a body depth of 4-5 cm, much deeper bodied than females. Spawning females produce between 100 and 200 eggs, spawning a number of times daily for several days. Eggs adhere to water plants and hatching occurs after 6-10 days, depending on temperature.
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| Lake Kutubu - photo© Allan Travers |
Remarks
Australian Patrol Officer T. Terrell first collected this species in Lake Kutubu during 1955. He sent preserved specimens to Australian ichthyologist Ian Munro, who in 1964 described them as Melanotaenia lacustris. Ian Munro (1919-1994) worked with the CSIRO Division of Fisheries Research and was an early pioneer in the identification of Australian and New Guinea Rainbowfishes. Not only was he a highly regarded ichthyologist but an accomplished aquarist as well and maintained many Australian and New Guinea rainbowfish species. During the 1960's he was maintaining New Guinea rainbowfish species such as Melanotaenia papuae, Melanotaenia sexlineata and Melanotaenia goldiei in captivity. Although at the time Melanotaenia papuae and Melanotaenia sexlineata had not been scientifically described. He later went on to publish "The Fishes of New Guinea" in 1967.
© Copyright Adrian R. Tappin
Updated January, 2007.
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