Melanotaenia etnaensis (male) - photo© Andreas Wagnitz

Melanotaenia etnaensis

Species Summary
Adult male Melanotaenia etnaensis are bluish grey dorsally on the head and back, ventral half of body with large bluish patch above the pelvic fins and yellowish patch with blue-black scale margins on the middle portion of the lower side (above anterior half of anal fin), grading to tapering bluish area above posterior half of anal fin; conspicuous blackish mid-lateral stripe from eye to caudal-fin base, widest portion on posterior caudal peduncle where it covers about two horizontal scale rows; narrow orange stripe between each scale row on side of body (most conspicuous on upper side); longitudinal yellowish zone on side immediately below blackish mid-lateral stripe, most vivid on lower caudal peduncle; upper part of opercle (below black stripe) silvery, punctuated posteriorly with small red spot; first dorsal fin bluish; second dorsal and fins yellowish on basal half, translucent to reddish on outer half; caudal fin pale grey; pelvic fins pale yellowish; pectoral fins translucent. Large males in particular exhibit a strong, well-contrasted dark mid-lateral stripe, yellow scales on the middle of the lower side, and yellowish to reddish dorsal and anal fins, the latter usually with a yellow basal stripe. Colour pattern of female similar to that of male except generally less vivid.

Melanotaenia etnaensis 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. Specimens collected from the Pama River by H. Bleher in 2013 have a notably different colour pattern and appear to mature at a much smaller size than other Etna Bay populations. However, on the basis of genetic analysis, they are essentially identical to the population from the Amabalanga type locality. 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.

Melanotaenia etnaensis (male) - photo© Andreas Wagnitz

Distribution & Habitat
Melanotaenia etnaensis is apparently confined to streams mainly flowing into Etna Bay, West Papua or in its immediate vicinity. The bay is situated on the southern coast of New Guinea, approximately 100 km southeast of the town of Kaimana. This large bay extends for approximately 55 km inland, progressively narrowing from the 15 km-wide mouth to the inner sections, which average only 1-2 km in width. The bay is spectacularly scenic with rainforest-covered mountains rising to over 1,000 m around much of the periphery with the exception of the southwestern section, which is low-lying swampland. Numerous creeks and small rivers flow into the bay throughout its length. Melanotaenia etnaensis have been collected or observed in the Ambalanga River, a small river situated at the mouth of the bay, and also from several small creeks flowing into the extreme inner portion. The habitat generally consists of rainforest (both primary and second growth) streams and the fish is generally found in deeper pools littered with fallen logs and branches. Temperature and pH recorded by Heiko Bleher during February 2013 at the Ambalanga River and Pama River ranged from 25.3-27.8°C and 7.4-8.8, respectively.

Remarks
Melanotaenia etnaensis was named "etnaensis" with reference to the Etna Bay type locality.

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