Melanotaenia fredericki (male) Samson River - photo© Laurent Pouyaud

Melanotaenia fredericki

Species Summary
The basic body colour of Melanotaenia fredericki is mauve with blue reflective scales above the midlateral band. They have broad yellow shading immediately below the midlateral band on the middle of the body (most prominent in juveniles). Mature fish sometimes show the yellow colouration only on the scale edges. The fins are mainly translucent, but the dorsal, anal and caudal may have a hint of yellow or red. Males may reach a maximum size of 12 cm, but females usually less than 10 cm. Males are more brightly coloured, larger, and deeper bodied than females.

Melanotaenia fredericki was described in 1939 by Henry W. Fowler on the basis of very young specimens (22-28 mm) found in the vicinity of Sainkedoek, on the Vogelkop Peninsula. They were collected during the Denison-Crockett South Pacific Expedition in 1937-1938 from a small stream in the Samson River catchment. They were name "fredericki" after Frederick Crockett, who organised the expedition in 1936. Gerald Allen wasn't certain whether M. fredericki represented a valid species. In his book "Rainbowfishes of Australia and New Guinea" in 1982, he treated Fowler's Charisella fredericki, as it was originally named, as a synonym of Melanotaenia goldiei. However, adult specimens collected in 1989 by Gerry Allen confirmed their validity as a distinct species.

Melanotaenia fredericki (female) Samson River - photo© Laurent Pouyaud

Distribution & Habitat
Melanotaenia fredericki are currently found in the westernmost portion of the Vogelkop Peninsula. They have been collected from clear slow flowing streams in closed canopy rainforest - pH 6.5~7.5; Temperature 24~28°C. Usually found around sub-surface vegetation, submerged logs, or branches.

Melanotaenia fredericki - photo© Gary Lange

Remarks
A number of rainbowfishes were collected by Heiko Bleher in 1992 from a small unnamed creek about 35 km south of Sorong and distributed in the international aquarium hobby as Melanotaenia fredericki. This variety is still being maintained in the hobby today (see below). In 2007, specimens believed to be Melanotaenia fredericki were collected from the Samson River, about 25 km east of Sorong. Then in 2008 fish resembling this variety became available in the commercial aquarium trade from an unknown source in Indonesia (above). The origin of this form is unknown. I have some doubt however, as to whether the specimens collected by Heiko Bleher, and the Samson River forms are the same species. They look very much like Melanotaenia misoolensis?

Rainbowfish species collected by Heiko Bleher in 1992 - photo© Neil Armstrong

Literature
Allen G.R. (1991) Field guide to the freshwater fishes of New Guinea. Christensen Research Institute, Madang, Papua New Guinea.

Fowler H.W. (1939) Zoological results of the Denison-Crockett South Pacific Expedition for the Academy of Natural Sciences of Philadelphia, 1937-1938. Part III.--The fishes.

Adrian R. Tappin
Updated June, 2016