Melanotaenia mamahensis (male) - photo© Andreas Wagnitz

Melanotaenia mamahensis

Species Summary
Adult male Melanotaenia mamahensis are brown dorsally on head and predorsal midline, bluish grey on side of nape and most of upper back; blue midlateral stripe from eye to caudal-fin base, usually darkest and widest on caudal peduncle where it covers 1.5-2 horizontal scale rows; narrow orange stripe between each scale row on upper half of side; relatively broad yellow zone immediately above and parallel to dark midlateral blue stripe, occupying 1-2 scale rows; lower side pale bluish to light grey with whitish spot on centre of each scale; opercle and lower half of head whitish or pale greyish, usually with silvery reflections and red spot (about one-half pupil size) on upper rear corner of opercle; first dorsal fin reddish anteriorly, grading to bluish posteriorly; second dorsal fin reddish to yellowish; anal fin red basally and mainly translucent bluish on outer half; caudal fin dusky greyish; pelvic fins white; pectoral fins mainly translucent.

Melanotaenia mamahensis (female) - photo© Andreas Wagnitz

Melanotaenia mamahensis is a member of the "Goldiei" rainbowfish group that share a wide range of morphological and meristic features and lack notable differences, as would be expected for closely related species. Due to their great similarity, the species belonging to the "Goldiei" group are most reliably distinguished on the basis of genetic differences, colouration, and their geographically isolated distribution. The challenge with the "Goldiei" species group is that while they all have strong genetic differences and some clear colouration differences, morphological and meristic differences are minimal in most cases. Adult males of M. mamahensis are distinguished by a broad yellow zone above the mid-lateral stripe and yellowish scale margins on the back, which exhibit variable intensity.

Mamah River Habitat - photo© Andreas Wagnitz

Distribution & Habitat
Melanotaenia mamahensis is currently known only from the Mamah River, a small stream situated about 50 km west of Nabire, near the edge of Cenderawasih Bay. The habitat consists of a clear, slow-flowing rainforest stream. The species was reported as abundant, swimming in large groups, especially in the deeper, shaded sections. Temperature and pH values of 26.3°C and 7.9 respectively were recorded at the time of collection (January 2015).

Mamah River Habitat - photo© Andreas Wagnitz

Remarks
Live specimens were collected by Hans-Georg Evers, Jeffrey Christian and Andreas Wagnitz from the Mamah River in 2015, and distributed in the aquarium hobby.

Literature
Allen G.R., P.J. Unmack and R.K. Hadiaty (2016) The Goldiei group of rainbowfishes (Melanotaeniidae) from the Birds Neck Region of New Guinea (Papua and West Papua Provinces, Indonesia) with descriptions of five new species and recognition of Melanotaenia dumasi Weber. aqua, International Journal of Ichthyology 22(1): 1-32.

Adrian R. Tappin
Updated June, 2016