Sepik Rainbowfish

The Sepik Rainbowfish (Glossolepis multisquamata) is a freshwater fish in the family Melanotaeniidae, native to the floodplain lakes, swamps, and slow-flowing waters of the Sepik River system in northern Papua New Guinea. Its species name refers to its unusually high number of small scales compared to related rainbowfish, giving rise to common names such as 'million-scale rainbowfish.' Like other members of the genus Glossolepis, it has a notably deep, laterally compressed body. The species is well adapted to the seasonally fluctuating floodplain habitats of the lower Sepik River, one of Papua New Guinea's major river systems.

Sepik Rainbowfish are deep-bodied fish typically reaching 10-14 cm.

• Body: deep and laterally compressed with a strongly arched back, characteristic of the genus Glossolepis
• Scales: notably fine and numerous compared to related species, giving a smooth, dense-scaled appearance
• Male coloration: coppery-orange to olive iridescence
• Fins: two separate dorsal fins; translucent, yellowish unpaired fins
• Tail: forked The unusually fine, densely packed scalation combined with the deep Glossolepis body shape helps distinguish this species from other rainbowfish sharing similar Papua New Guinea floodplain habitats.

This species inhabits the floodplain lakes, oxbows, swamps, and slow-moving backwaters of the lower and middle Sepik River system in northern Papua New Guinea. These floodplain habitats are subject to significant seasonal water level fluctuations tied to monsoonal rainfall patterns, creating a dynamic mosaic of open water, flooded vegetation, and swamp margins. Sepik Rainbowfish favor warm, often turbid, nutrient-rich floodplain waters with abundant aquatic and marginal vegetation. Their adaptation to these fluctuating floodplain conditions distinguishes their ecology from rainbowfish species restricted to stable lake systems elsewhere in New Guinea.

Sepik Rainbowfish school within floodplain lakes and swamp channels, moving between open water and vegetated margins as water levels shift seasonally. They feed omnivorously on small invertebrates, algae, and organic detritus available in the productive, nutrient-rich floodplain waters of the Sepik system. Breeding activity is closely tied to the seasonal flood cycle, with rising waters providing expanded vegetated spawning habitat where eggs are scattered and left unguarded among aquatic plants. As an abundant floodplain species, Sepik Rainbowfish play an important ecological role both as consumers of small invertebrates and as prey for larger fish and waterbirds across the Sepik basin.