Red rainbowfish  (Glossolepis incisus)

Classified as Vulnerable (VU) on the IUCN Red List (1).

Like other rainbowfish, the red rainbowfish is a small freshwater fish with a rather compressed body and bright colouration (3) (4) (5). As the common name suggests, the male red rainbowfish has a bright salmon-red body, with an attractive silvery sheen on some of the scales (2) (5) (6). The female is much less vibrantly coloured, with a yellowish-olive body, a silvery or golden sheen to the scales, and clear fins. Young red rainbowfish are duller olive-green in colour, only starting to gain the adult colouration at a body length of four to five centimetres (2) (6). The male red rainbowfish grows to a larger size than the female, and typically has a deeper body, with a high, rounded back that makes the head appear disproportionately small (2). The red rainbowfish has two long dorsal fins, a long anal fin, and a deeply forked caudal fin (3) (5).

The red rainbowfish is endemic to Lake Sentani and its tributaries, in Irian Jaya, Indonesia (1) (2) (5) (6) (7).

The single freshwater lake in which the red rainbowfish occurs is approximately 30 kilometres long and up to 19 kilometres wide, and situated at around 75 metres above sea level (1) (2) (6) (7). Surrounded by hills and mountains, the lake has clear water and is densely vegetated (6). Rainbowfish are reported to be found mainly at the lake margins, congregating around areas of aquatic vegetation and fallen logs (2).

Very little information is available on the biology of the red rainbowfish. Like other members of the rainbowfish family (Melanotaeniidae), it is likely to be a schooling species, and to eat a variety of items including aquatic insects, small crustaceans and algae. Breeding may occur year-round, but is often stimulated by the onset of the rainy season (3). The eggs may be laid in aquatic vegetation (3), and in captivity a female red rainbowfish can release up to 50 eggs a day, the eggs hatching after about a week (3) (4) (6). Most rainbowfish reach sexual maturity within the first year (3).

An increasing human population around Lake Sentani has led to pollution of the lake with domestic waste, threatening species such as the red rainbowfish (1). In addition, the red rainbowfish may be caught for food (4) (6), and is under further threat from the introduction of exotic fish species, including carp, barbs and tilapia (1). As in many rainbowfish, the red rainbowfish’s bright colouration has also made it popular in the aquarium trade (2) (3) (6) (7), but the current impacts on the wild population are unknown.

There are not known to be any specific conservation measures in place for the red rainbowfish. Further research into the species and the threats it faces are likely to be needed before any appropriate action can be taken to protect the wild population.

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about the red rainbowfish see:

• Fishbase:
  http://www.fishbase.org/summary/SpeciesSummary.php?id=10477
• Home of the Rainbowfish: Glossolepis incisus:
  http://members.optushome.com.au/rainbowfishes/Incisus.htm