Melanotaenia irianjaya (Hoa Creek) - photo© Gerald Allen

Melanotaenia irianjaya

Species Summary
Male specimens of Melanotaenia irianjaya have a bluish-grey or slightly violet on the upper half of the body while the lower half of the body is silvery-white with a slight yellow hue posteriorly. There is a broad, bluish midlateral band, which is most prominent on the rear-half of the body. The dorsal and anal fins are reddish with narrow white margins. The caudal fin is reddish and has distinctive black upper and lower margins. The pelvic and pectoral fins are mainly transparent.

Melanotaenia irianjaya does not appear to be closely related to other members of the genus. This species is unusual in having the middle rays of the dorsal and anal fins longer than the other rays. Instead the middle rays of these fins are the longest, a feature shared only by Melanotaenia corona from north-central New Guinea. Additionally, it appears to lack pronounced sexual dimorphism, a feature which is prominent in most other Melanotaenia. Although most collected specimens were small (under 50 mm SL), a few were sexually mature, but it was necessary to examine the gonads to determine sex. Males may reach a maximum size of 12 cm, but females are usually less than 10 cm. Unlike most rainbowfishes, males of this species lack the pronounced elongation of the posterior dorsal and anal fin rays. Males are more brightly coloured, larger, and deeper bodied than females.

Distribution & Habitat
Melanotaenia irianjaya are found primarily in river systems that drain into Bintuni Bay, in the southern Vogelkop Peninsular region. Other collections have been from a tributary of the Kamundan River at Senopi Village on the north side of Bintuni Bay. They have also been collected from Wat Creek, near the village of Fruata on the Bomberai Peninsula. In 2000, live specimens were collected from the Bintuni East River and the Tisbo River.

Habitats consist of rainforest streams ranging from slightly turbid and slow flowing over flat terrain to clear, moderately fast flowing through hills. Temperature and pH values range from 27-28°C and 7.3-7.8 respectively. The fish are found in areas with relatively few aquatic plants, over gravel or sand bottoms, often in the vicinity of submerged logs.

Remarks
Live specimens were collected by Heiko Bleher in 1982 and distribution to the aquarium trade in 1983.

Literature
Allen, G. R. (1985) Three new rainbowfishes (Melanotaeniidae) from Irian Jaya and Papua New Guinea. Revue française d'Aquariologie 12 (2): 53-62.

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

Adrian R. Tappin
Updated December, 2008.