Salmon-red Rainbowfish

The Salmon-red Rainbowfish (Glossolepis incisus) is a freshwater fish in the family Melanotaeniidae, endemic to Lake Sentani, a single lake system in the Papua province of Indonesia. It belongs to the genus Glossolepis, whose members are generally deeper-bodied and more strongly colored than typical Melanotaenia rainbowfish. First described in 1907, it has become one of the most recognizable rainbowfish species due to the intense red coloration developed by mature males. Because it is restricted to one lake and its associated tributaries, the species is considered vulnerable to habitat changes affecting Lake Sentani, including sedimentation and water quality decline.

Salmon-red Rainbowfish grow to about 10-12 cm and are among the deepest-bodied rainbowfish.

• Body: strongly compressed with a pronounced arched back, especially in males
• Male coloration: vivid salmon-red to orange over the entire body
• Female/juvenile coloration: olive-silver, far less vivid than males
• Fins: two dorsal fins, reddish-tinted unpaired fins in males
• Tail: forked The combination of an unusually deep, arched body shape with an all-over red coloration in mature males is diagnostic and separates it from most other rainbowfish, which typically show striping or spotting rather than uniform red coloration.

This species is endemic to Lake Sentani and its immediate tributary streams near Jayapura in Papua, Indonesia, and is not found naturally anywhere else. It inhabits open water as well as vegetated shallows and inflow streams around the lake, in warm tropical lowland conditions typical of New Guinea. Because Lake Sentani is its sole natural habitat, the species is closely tied to the lake's overall water quality and hydrology. Human activity around the lake, including sedimentation, deforestation of the surrounding catchment, and pollution, poses ongoing pressure on the wild population's habitat.

Salmon-red Rainbowfish form schools that move through open lake water and along vegetated shoreline areas, feeding on small invertebrates, algae, and organic matter in a generalist, omnivorous manner. Males display heightened red coloration and engage in courtship behavior near vegetation or structure to attract females, with fertilized eggs scattered and adhering to plants or roots; there is no parental care of eggs or young. As a lake-dwelling schooling species, it interacts with other native Lake Sentani fish and invertebrates, occupying a role as both a mid-level predator of small prey and as prey itself for larger fish and birds around the lake.