Melanotaenia ajamaruensis

Allen and Cross, 1980
Ajamaru Rainbowfish

Species Summary
The natural colouration of Melanotaenia ajamaruensis is not known as no live specimens have been collected. The type specimens preserved in the Leiden museum are the only ones ever collected. From field notes they have a metallic blue to yellowish or green with orange and yellow longitudinal stripes and dark scale edges. The body is ovate and laterally compressed. They grow to a length of around 11 cm, males are usually deeper bodied than females. Named ajamaruensis with reference to the Ajamaru Lakes, the type locality and only known collection site for this species thus far (see remarks).

Distribution & Habitat
Melanotaenia ajamaruensis is a lake and stream dwelling rainbowfish found in relatively clear alkaline water, with abundant aquatic vegetation. Museum specimens were collected in March 1955 by Marinus Boeseman and his companions in the Ajamaru Lakes, a complex of lakes on the Ajamaru River in the centre of the Vogelkop Peninsula, West Papua. The Ajamaru Lakes are located about 120 km East-South-East of Sorong. There are three small freshwater lakes and associated marshes. The largest lake, Lake Ayamaru (Amaru, Ajamaroe), drains east via the other two lakes, Lake Hain and Lake Aitinjo (Aytinjo), into an upper tributary of the Kais River and eventually into the Ceram Sea.

Lake Ayamaru is a 20 metre deep, 2,200 hectare blackwater lake in a rather flat terrain, located at about 250 metres altitude. In the wetter months (April-June) the lake can rise by up to 5 metres from its dry season level; it never dries out completely, but the shoreline recedes several hundred metres. It has a muddy bottom, and the sediments of the shores are reportedly white, either sand or kaolin clay. There are several small villages around the lake. The lakes and streams have a pH of 6.4-7.8 (de Vries, 1962) and temperate 26-27°C. When Marinus Boeseman collected his specimens, he reported a pH of 6.4-6.5.

As early as 1938, Trichogaster pectoralis, Helostoma temminckii and Cyprinus carpio were introduced into Lake Ayamaru to supply the requirements of a Dutch military post in that area. The two first-mentioned species are still found there as a result of a highly successful acclimatisation. Cyprinus carpio was introduced to the lake in 1938, 1951 and 1969.

Melanotaenia ajamaruensis, Melanotaenia boesemani, Pseudomugil reticulatus and Glossogobius hoesei have been reported from the lakes and surrounding streams. Other species reported as occurring are Chaenogobius isaza, Arius spp. (one is cream-coloured and the other black) and Glossamia sp. There are apparently reliable reports that large eels also occur in the Aytinjo Lake. Crayfish are abundant in the lakes. Two species have been observed, one of which attains about 5 cm in length and the other about 10 cm (Cherax holthuisi was collected by M. Boeseman in 1952 from the Kais River). Also, possibly three species of giant prawns (Macrobrachium), which local have named according to their colour: udang biru (blue), udang hitam (black), and udang putih (white, but occasionally with some reddish-orange). However, very little research has been carried out, and it is possible that other species occur in the lakes.

Remarks
From October 1954 through to May 1955 Marinus Boeseman took part in a collecting expedition for the Rijksmuseum van Natuurlijke Historie to Netherlands New Guinea (West Papua) with L.D. Brongersma and L.B. Holthuis. His task was to provide a thorough knowledge of the fish fauna by intensively surveying as many rivers and lakes as possible in West Papua. This task was taken to heart and in a relatively short period many localities were visited, resulting in a rich collection for the museum in Leiden. Among the places he visited was Lake Sentani, Tami River, Biak Island, Lake Jamoer (Yamur), Wissel Lakes, Ayamaru Lakes, Lake Aitinjo, Merauke and the Digul River. This collection included many rainbowfishes, but a thorough study of this material and descriptions of all the new species was never made by Boeseman.

As part of his preparation for the revision of the rainbowfish family, Gerald Allen studied the Dutch collection of 1954-55 at the end of the 1970's. He discovered no less than four new rainbowfish species, which he described in 1980 together with Norbert Cross. These species were Melanotaenia boesemani, M. ajamaruensis, M. japenensis and Glossolepis pseudoincisus.

In 2007-2008, a number of surveys were conducted by the Papuan National Marine and Fisheries Research, the Academy of Fishery Sorong, and the Institute of Research for Development of France in five bioregions of West Papua. Approximately fifteen species of rainbowfishes were collected during these expeditions which included M. ajamaruensis from Lake Aitinyo (Aytinjo). What has become of the fish collected during these expeditions is not known to me!

Literature
Allen, G. R. and N. J. Cross (1980). Description of Five New Rainbowfishes (Melanotaeniidae) from New Guinea. Records of the Western Australian Museum 8 (3): 377-96.

Boeseman, M. (1956). The Lake Resources of Netherlands New Guinea. South Pacific Commission Quarterly Bulletin 6(1): 23-25.

Boeseman, M. (1956). Fresh-water sawfishes and sharks in Netherlands New Guinea. Science 123: 222-223.

Boeseman, M., (1963). Notes on the fishes of Western New Guinea. Zoologische Mededelingen Leiden 38 (14): 221-242.

de Vries, J. (1962). Review of Inland Fisheries in Netherlands New Guinea. South Pacific Commission Fisheries Technical Meeting (Noumea, 5 - 13 February 1962).

Holthuis, L.B., (1956). Native fisheries of freshwater Crustacea in Netherlands New Guinea. Contributions to New Guinea Carcinology. I. - Nova Guinea (n. ser.) 7(2): 123-137.

Reeskamp, G.A. (1961). Report of a Preliminary Survey of the Ajamaroe Lakes, Netherlands New Guinea. Indo-Pacific Fisheries Council - Occasional Paper 61/12. Food and Agricultural Organization of the United Nations.