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| Chilatherina sentaniensis [Wild Caught] - photo© Gerald Allen |
(Weber, 1907)
Sentani Rainbowfish
Species Summary
Perhaps the most distinguishing feature of the Chilatherina genus is their deep, laterally compressed body that increases with age, particularly in males, and Chilatherina sentaniensis is no different. Their overall body colouration is silvery-blue or greenish on the upper back fading laterally to silverly-orange. They have a diffuse blue or green mid-lateral stripe and narrow silver or light blue stripes between each horizontal scale rows. However, colour can be variable depending on captive conditions. They may reach a maximum size of 12 cm, but are usually less than 10 cm. Males are more brightly coloured, larger, and deeper bodied than females.
Distribution & Habitat
Chilatherina sentaniensis was originally collected by Max Weber during the Siboga Expedition in the Dutch East Indies (West Papua) between 1890 and 1900. They are endemic to Lake Sentani and its tributaries streams. Lake Sentani is located some 10 kilometres west of Jayapura at the NE extremity of West Papua. It is an irregularly shaped lake with approximate dimensions of 28 km (E-W) by 19 km (N-S) and a surface area of 104 km². Its blue-green waters are dotted with at least 16 small islands, and it is surrounded by hillsides in the south and the Cyclops Mountains in the north, which separate the lake from the Pacific Ocean. Lake Sentani is by far the largest of the West Papuan lakes and has a catchment area of about 600 km². About 35 small rivers flow into the lake, and there is one natural outlet in the south-eastern tip, via the Jafuri and Tami rivers to the Pacific Ocean near the Papua New Guinea border.
The lake is divided into three main sections with recorded depths of 7 to 52 metres. According to surveys in 1970-71, 1984 and 1987 the lake is thermally unstratified, with surface temperatures of 29-32° and pH 6.2 - 6.8. Rainbowfishes are generally found around the margins of the lake. Large numbers are found congregating around submerged aquatic vegetation, fallen tree branches etc.
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| Lake Sentani |
Because of its proximity to the provincial capital Jayapura and the large population around it, Sentani is no longer the pristine lake it once was. A survey by Samuel J. Renyaan in 1993 recorded 33 species of fish, of which 13 were introduced. Surveys have shown an increase in introduced species but the impact on the total fish population has not been documented. Fish are extensively raised in ponds and cages around the perimeter of the lake and the introduction of species (particularly carp and tilapia) has been both accidental and intentional.
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| Chilatherina sentaniensis [Aquarium Population] - photo© Christophe Mailliet |
Remarks
A large collection of specimens were obtained from the lake by Dr. M. Boeseman of the Leiden Museum in 1954. Gerald Allen collected specimens in a single small tributary stream flowing into the north-eastern end. Several specimens were netted along with Chilatherina fasciata and Glossolepis incisus. Live specimens were reportedly collected for the aquarium hobby in 1982. What eventually happened to the fish from this collection has been lost in the pages of aquarium history.
In 1983, live specimens of Chilatherina fasciata were collected from the Jafuri River and during the 1980s and early 1990s they were being distributed in the hobby as Chilatherina sentaniensis. In his "Field Guide to the Freshwater Fishes of New Guinea" in 1991 Gerald Allen noted that probably all records of Chilatherina sentaniensis in the aquarium literature actually related to Chilatherina fasciata varieties. The problem with misnomers is that they seem to persist and it is still causing a great deal of confusion among hobbyists as to which fish is the true sentaniensis.
However, the "genuine" Chilatherina sentaniensis does exist in the hobby and they have a much longer, more pointed head and usually 9-10 soft dorsal rays compared to 12-14 rays in Chilatherina fasciata. Live specimens were collected from the lake in 1991 by Charles Nishihira and distributed in the aquarium hobby. Specimens were also collected from a small tributary stream in 2004 and 2005. However, they have not been widely available and only a handful of enthusiasts are maintaining them in captivity.
© Copyright Adrian R. Tappin
Created December, 2001
Updated May, 2008
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