arowana

Asian arowana refers to four species of freshwater fish in the genus Scleropages. Some sources differentiate these varieties into multiple species,^[2][3] while others consider the different strains to belong to a single species, Scleropages formosus.^[4] They have several other common names, including Asian bonytongue, dragon fish, and a number of names specific to different varieties.

Native to Southeast Asia, Asian arowanas inhabit blackwater rivers, slow-moving waters flowing through forested swamps and wetlands. Adults feed on other fish, while juveniles feed on insects.^[5]

These popular aquarium fish have special cultural significance in areas influenced by Chinese culture. The name dragon fish stems from their resemblance to the Chinese dragon. This popularity has had both positive and negative effects on their status as endangered species.

Several distinct, naturally occurring colour varieties are recognised, each found in a specific geographic region. They include the following:

• The green is the most common variety, found in Vietnam, Myanmar, Thailand, Cambodia, and Malaysia.
• The silver Asian (not to be confused with the silver arowana, Osteoglossum bicirrhosum) is considered part of the green variety by some. It has two subvarieties, the "grey tail silver" or "Pinoh arowana," and the "yellow tail silver," each found in a different part of the island of Borneo in Indonesia.
• The red-tailed golden is found in northern Sumatra, Indonesia.
• The gold crossback, blue Malayan, or Bukit Merah blue is native to the state of Pahang and Bukit Merah area in Perak, Malaysia.
• The red, super red, blood red, or chili red is known only from the upper part of the Kapuas River in western Borneo, Indonesia.

Green arowanas are dark green on the back, silvery or golden green on its sides, and silvery or whitish on its ventral surface, with dark greenish or bluish patches visible through the lateral scales. In mature fish, the top of the eye and the head behind the eye are bright emerald.^[2]

Both grey-tailed and yellow-tailed silver Asian arowanas are dark grey on the back and silver on the sides, with dark ring patches on the lateral scales and a silvery or whitish belly. In yellow-tailed specimens, the fin membranes are yellowish with dark grey rays. In grey-tailed specimens, the fins are uniform dark grey.^[2]

Red-tailed golden arowana. Although the scales are golden, the anal and caudal fins are reddish-brown.

Mature red-tailed golden arowanas have brilliant metallic gold lateral scales, gill covers, bellies, and pectoral and pelvic fin membranes, although the back is dark. In juveniles the areas destined to develop golden colour start out metallic silver. The anal fin and the bottom portion of the caudal fin are light brown to dark red.^[2]

Mature gold crossback arowanas are distinguished from the red-tailed golden arowanas by having metallic gold crossing the back completely. This variety also lacks the reddish fins of the red-tailed golden.^[13]

In mature super red arowanas, the gill covers, lateral scales, and fin membranes of these fishes are metallic red, with the exact hue varying from gold-tinged to deep red. The back is dark brown. In juveniles, the darker the dorsal colouration, the deeper the red will be on maturity.