Taxonomy & naming
Melanotaenia salawati was described in 2011 by Kadarusman, Sudarto, Jacques Slembrouck and Laurent Pouyaud in the journal Cybium (volume 35, issue 3, pages 223–230), based on a series of sixteen specimens collected on Salawati Island in the Raja Ampat group of West Papua, Indonesia. Eschmeyer's Catalog of Fishes records the valid name as Melanotaenia salawati Kadarusman, Sudarto, Slembrouck & Pouyaud, 2011; because the species was described in Melanotaenia, where it remains, the authority is cited without parentheses.
The species belongs to the genus Melanotaenia, the largest in the family Melanotaeniidae — the true rainbowfishes — which radiate across New Guinea and northern and eastern Australia. M. salawati is one of several closely related rainbowfishes from the islands fringing the Bird's Head Peninsula, and the original authors separated it from its nearest relatives on fine meristic and morphometric grounds. From M. batanta of neighbouring Batanta Island it differs in a shorter snout, longer caudal peduncle, longer dorsal-fin bases, and more cheek scales; from M. fredericki, in a longer snout, larger interorbital width, shorter second-dorsal spine, longer anal-fin base, and higher counts of cheek scales and gill rakers. These are subtle differences rather than dramatic ones — the signature of a young radiation spread thinly across the islands and rivers of the region.
Morphology
Melanotaenia salawati is a small rainbowfish, reaching a maximum recorded length of about 3.5 in standard length. The body is fusiform — the normal, moderately elongate rainbowfish form rather than the deep diamond-shaped profile of some of its larger relatives — and laterally compressed in cross-section, with the divided dorsal fin characteristic of the family: a short anterior dorsal followed by a longer posterior dorsal.
The features separating it from its island neighbours are largely meristic and proportional: relative snout and caudal-peduncle length, the lengths of the dorsal- and anal-fin bases, interorbital width, and counts of cheek scales and gill rakers. Published descriptions of live colour are thin, and FishBase carries no photograph. As in rainbowfishes generally, mature males are probably more intensely coloured and somewhat deeper-bodied than females, with display colours that come and go with mood and condition — but the colour data for M. salawati is too sparse to do more than guess from showier relatives.
Habitat
The species is endemic to the freshwater habitats of Salawati Island, in the Raja Ampat group immediately west of the Bird's Head Peninsula of West Papua, Indonesia. It is a strictly freshwater, pelagic, tropical fish, occupying the streams and inland waters of the island. The original collection of sixteen type specimens came from these Salawati freshwater habitats; no occurrence outside the island is recorded.
No habitat measurements specific to M. salawati have been published in the sources at hand, so the picture has to be borrowed cautiously from the genus. New Guinea rainbowfishes generally live in clear rainforest streams, often around submerged logs and branches and among marginal and aquatic plants, in warm water broadly between about 18 and 82 °F. Those are genus-level figures, not measurements from Salawati; the actual temperature, pH, and hardness of the species' streams go unrecorded here.
Feeding
No feeding study exists for Melanotaenia salawati. FishBase models its trophic level at roughly 2.9, consistent with an omnivore taking a mix of small animal and plant material. Judging by the genus, it is likely an opportunistic feeder working the upper and middle water column — insect larvae, small crustaceans, and surface insects, plus algae and plant matter grazed off submerged surfaces.
Since the fish is rarely if ever traded, there is no aquarium feeding experience to draw on. By analogy with better-known relatives, it would take good-quality flake and small pellets alongside frozen and live foods — Daphnia, brine shrimp, bloodworm — with a varied diet improving colour and condition. That is extrapolation from rainbowfish husbandry, not observation of this species, and is offered as such.
Mating
There is no published account of courtship or mating specific to Melanotaenia salawati. Within the genus and family, rainbowfishes are egg-scattering, plant-spawning species with no parental care, and they tend to spawn over an extended period rather than in a single seasonal event. Males typically establish display areas and court females with intensified colour and fin-flaring, and many species show a flickering pale courtship band along the head and nape of a displaying male, most vivid in the early morning.
Whether M. salawati follows the pattern in every detail is unrecorded, but the rainbowfish reproductive strategy is conserved enough across the genus that the broad outline — competitive male display, morning spawning, pairing within fine vegetation — is a fair expectation. Species-level behaviour is simply absent from the present sources, and is flagged here as a gap rather than filled with guesswork.
Breeding
No captive-breeding record for Melanotaenia salawati appears in the available sources; this obscure 2011 island endemic has essentially no hobby literature and is rarely, if ever, kept. What can be said is drawn from the reproductive biology of the genus. Rainbowfishes are egg-scatterers that lay small, adhesive eggs which attach by fine filaments to fine-leaved plants or spawning mops, with a female releasing a few eggs at a time over many days rather than a single clutch, and with adults offering no parental care.
Incubation in related Melanotaenia usually runs about one to two weeks at normal tropical temperatures, the tiny fry needing very small first foods before they can manage newly hatched brine shrimp. Whether M. salawati matches in clutch size, egg size, and incubation period is undocumented. FishBase rates its resilience as medium, with an estimated population doubling time of 1.4 to 4.4 years — a coarse demographic figure, not a breeding protocol. Anyone attempting this species would be working without a published baseline.
In the aquarium
Melanotaenia salawati is, for practical purposes, an unknown quantity in the aquarium. FishBase notes it as a species of potential aquarium interest, but no dedicated hobby species page or care account was located, and the fish is rarely if ever encountered in the trade. There is therefore no established husbandry record to report, and any keeping advice must be flagged as generalised from rainbowfish norms rather than tested on this species.
On that basis, a keeper would treat it like other small New Guinea rainbowfishes: an active, peaceful schooling fish kept in a group with open swimming space, warm water in the low-to-mid 20s Celsius, good filtration, stable conditions, and similarly sized peaceful tankmates. At an adult size under 4 in, a modest but elongate planted tank would suit a group. All extrapolation, though — the water chemistry, temperament, and colour development of M. salawati in captivity are not documented in the present sources.
Conservation
Melanotaenia salawati is assessed as Near Threatened (NT) on the IUCN Red List, under criterion B2a, with the assessment dated 3 December 2019 (species ID 161110694). The Near Threatened listing under B2a reflects a restricted area of occupancy on Salawati Island that brings the species close to the thresholds for a threatened category without quite meeting them. The species is not evaluated under CITES or CMS, and FishBase rates its fishing vulnerability as low.
The core conservation problem is the one shared by many narrowly endemic island rainbowfishes: a fish confined to the freshwaters of a single island has little room to absorb local pressures — habitat alteration, or the introduction of non-native fishes — because no large outlying population is there to buffer the decline. M. salawati is not heavily collected; it is far too obscure for that. But its small total range keeps it inherently sensitive. Protecting Salawati's streams is the practical key to its survival, and the species is a reminder of how much of the Raja Ampat rainbowfish fauna is both newly described and confined to a single patch of ground.