Melanotaenia oktediensis

Melanotaenia oktediensis (wild-caught) - photo© Neil Armstrong

Allen and Cross, 1980
Oktedi Rainbowfish

Species Summary
Melanotaenia oktediensis have a body colouration that is coppery brown above a prominent mid-lateral line and pale mauve to white below. May reach a maximum size of 12 cm, but usually less than 10 cm.

Distribution & Habitat
Melanotaenia oktediensis are found in tributaries of the Ok Tedi River which is one of the main headwater streams of the upper Fly River system. Rather uncommon in the main river, which is mostly populated by Melanotaenia splendida rubrostriata. The tributaries of the Ok Tedi River are cool, clear, relatively fast flowing rainforest streams with rocky bottoms. Water conditions reported from this habitat are temperature 17-24° Celsius, pH 7.3~8.7, hardness 20~80 mg/L CaCO3 and a high dissolved oxygen content of 6.9~10.0 mg/L.

Remarks
Melanotaenia oktediensis were initially collected by C. Boyden in the Ok Tedi River at Tabubil, Papua New Guinea in 1974. In 1975, Dr. Tyson Roberts collected them from the lower portion of Karamonge Creek, a tributary of the Ok Tedi River during an ichthyological survey of the Fly River and mistakenly identified them as Melanotaenia vanheurni, a species found in the Mamberamo basin, northern New Guinea. After examining specimens in the Zoologisch Museum, Amsterdam and the American Museum of Natural History, New York, Allen and Cross recognised them as a distinct species and named them Melanotaenia oktediensis after the Ok Tedi River. Both species have a relatively elongated body shape, a prominent mid-lateral band, and are characterised by relatively numerous soft dorsal and anal fin rays. The most significant difference is the position and length of the mid-lateral band. Live specimens were introduced to the Australian hobby in 1982 and were spread to Europe and Northern America, but they have never been readily available.

Literature
Allen, G. R. and N. J. Cross (1980). Descriptions of five new rainbowfishes (Melanotaeniidae) from New Guinea. Records of the Western Australian Museum 8 (3): 377-396.

Allen, G.R. (1991) Field guide to the freshwater fishes of New Guinea. Christensen Research Institute, Madang, Papua New Guinea.