Melanotaenia albimarginata

Species Summary
Males of Melanotaenia albimarginata are brown dorsally on head, nape, and uppermost part of back; lower half of head pale grey with scaled area of preoperculum mainly yellow; middle of operculum yellow to pale reddish; iris yellow; upper half of side with dappled or variegated appearance due to presence of scattered pale bluish scales; also thin yellow stripes between each horizontal scale row on upper portion of side; midlateral dark grey stripe covering 1-2 horizontal scale rows from behind eye to caudal-fin base; an equally broad zone of yellow immediately below midlateral dark stripe, widest anteriorly; ventral portion of body (below yellow zone) pale grey; dorsal and anal fins with greyish membranes and whitish to pale yellow fin rays; first dorsal fin with small black spot at base of posteriormost portion of fin; caudal semitranslucent grey with prominent white area at tip of upper and lower lobes; pelvic fins dusky grey; pectoral fins translucent. Freshly collected live fish photographed in an aquarium were entirely bluish with reddish margins on the scales of the upper side and the second dorsal fin was marked with 2-3 rows of dark spots. The only colour pattern features shared with the in situ fish are the white tips on the caudal fin and whitish rays on the anal fin. Females similar to male except no dark midlateral stripe and yellow stripes between horizontal scale rows of side are more obvious. Also, the white tips on the caudal lobe are more diffuse and less obvious.

This species was named albimarginata with reference to the prominent white markings on the caudal fin lobes

Distribution & Habitat
Melanotaenia albimarginata is currently known only from Alur Warnafa, a tributary of Sungai Unmar, a small stream situated near the village of Algadang. The location is reached via Sungai Workai, a marine "river" that bisects the main island group. Sungai Unmar is reached via a 38 km transit from the west coast and then an additional 7 km upstream in fresh water. The lowermost km of the river is brackish and lined with mangrove. During a visit to the type locality in January 2013 the water was very clear and slow flowing with depths ranging from about 1-3 m. Water levels were generally higher with stronger current, and reduced visibility during another visit in December 2013 due to the onset of monsoonal rains. The bottom at this site consisted of a relatively smooth limestone pavement with few aquatic plants (Cryptocoryne ciliata), littered with leaf and log debris. Melanotaenia albimarginata repeatedly retreated among the dead branches of fallen trees when pursued. The stream formed a more or less open corridor lined with second growth forest and gardens. The pH and conductivity values for this site ranged from 8.04-8.64 (high tide) and 144-319 µS (high tide) respectively during the January 2013 visit. In addition, a water temperature of 27.4°C was recorded. Although the site is purely a freshwater habitat, water levels are influenced by the tides. Melanotaenia senckenbergianus was also observed at this site, but generally in smaller numbers. Other species that were recorded include Craterocephalus cf. randi, Ambassis interrupta, Glossamia aprion, Awaous acritosus, Glossogobius concavifrons, Redigobius bikolanus, Stiphodon atratus, Eleotris fusca and Oxyeleotris mertoni.

Literature
Allen G.R., R.K. Hadiaty, P.J. Unmack and M.V. Erdmann (2015) Rainbowfishes (Melanotaenia: Melanotaeniidae) of the Aru Islands, Indonesia with descriptions of five new species and redescription of M. patoti Weber and M. senckenbergianus Weber. aqua, International Journal of Ichthyology 21(2): 66-108.

Adrian R. Tappin
Updated June, 2015