Taxonomy & naming
Melanotaenia wokamensis was described in 2015 by Gerald R. Allen, Renny K. Hadiaty, Peter J. Unmack and Mark V. Erdmann in a paper revising the rainbowfishes of the Aru Islands, published in aqua, International Journal of Ichthyology (volume 21, pages 66–108). The holotype — an adult male of 3 in standard length — was collected in December 2013 from Sungai Torbol, a tributary of the Sungai Tunguwatu drainage on the western side of Wokam Island, in Maluku Province, Indonesia. Eschmeyer's Catalog of Fishes records the valid name as Melanotaenia wokamensis Allen, Hadiaty, Unmack & Erdmann, 2015; because it was described in Melanotaenia, where it remains, no parenthetical authority is used.
The specific epithet wokamensis refers directly to the type locality on Wokam Island. The genus name Melanotaenia combines the Greek roots for 'black' and 'band or stripe', a reference to the dark lateral stripe characteristic of many species in the genus. M. wokamensis belongs to the Aru Islands assemblage of rainbowfishes, placed by its describers near the 'Goldiei' group alongside its close Aru relatives M. kolaensis and M. picta. They separated it from those species on colour pattern, a deeper caudal peduncle, a deeper body, and supporting genetic evidence.
Morphology
Melanotaenia wokamensis is a small rainbowfish, reaching about 3 in standard length in males (roughly 4 in total length); females are smaller, to around 2.5 in standard length. Compared with its close Aru relatives — M. picta, M. kolaensis and M. senckenbergianus — it is markedly deeper-bodied — the greatest body depth of an adult male reaches about 34 percent of standard length — and it has a comparatively deep caudal peduncle. Meristic counts in the original description run to 4–6 dorsal spines, 11–14 dorsal soft rays, a single anal spine with 18–22 anal soft rays, 33–35 lateral-line scales, and usually 13 pectoral rays.
In life the markings are bold. The back is light blue with metallic reflections, and a dark blue midlateral stripe one to two scales wide runs along the flank, bordered above and below by reddish-to-orange stripes. The belly is greyish-white, and a large bright-blue patch sits behind and below the pectoral-fin base. The soft dorsal and anal fins are bluish with a broad reddish margin, and the caudal fin is semi-translucent reddish. As in rainbowfishes generally, colour intensity is mood- and condition-dependent, reaching its peak in displaying dominant males.
Habitat
The Wokam rainbowfish is known only from three tributaries of the Sungai Tunguwatu drainage — Sungai Torbol, Sungai Gaibel and Sungai Gayarfafeimusin — on the western side of Wokam Island in the Aru Islands. These are narrow watercourses, averaging only about 10–16 ft wide, running as limestone channels through lowland rainforest. The fish gathers in the deeper pools — up to about 5–7 ft deep — that form below the many small cascades and waterfalls along these streams.
During the rainy season the heavy afternoon showers send the streams into flash flood, so the species has to cope with sudden swings in flow in an otherwise sheltered forest setting. The original description does not report water-chemistry values such as pH, temperature or hardness for the habitat. Given the limestone catchment and the lowland tropical rainforest setting, the water is best characterised generally as warm and neutral-to-slightly-alkaline; precise figures are not available, and the data here are sparse.
Feeding
No detailed dietary study has been published for Melanotaenia wokamensis specifically, and direct data are sparse. FishBase gives an estimated trophic level of about 2.9, consistent with an omnivore that takes both animal and plant material rather than a strict carnivore or herbivore.
Like rainbowfishes generally, it can be expected to feed opportunistically in the upper and middle water column — insect larvae, small crustaceans, and insects taken at or near the surface — with algae and other plant material grazed from submerged surfaces. The plunge pools it favours below cascades collect drifting invertebrates and falling terrestrial insects, a dependable food supply for a small, active mid-water fish.
Mating
Specific breeding observations for Melanotaenia wokamensis in the wild have not been published, so the account here is drawn by analogy with the well-studied biology of the genus and noted as such. Rainbowfishes of the genus Melanotaenia are egg-scattering, plant-spawning fishes with no parental care. Males court with intense colour displays, flaring the fins and saturating the body colours, often with a flickering pale 'courtship band' running along the head and nape.
Display and spawning peak in the early hours after first light, and males show off hardest when rivals are present. In M. wokamensis the male's bright-blue pectoral patch, orange-bordered lateral stripe, and red-margined fins are the likely signals in courtship, though this has not been documented directly for the species.
Breeding
There are no published captive-breeding records specific to Melanotaenia wokamensis, and the species was only recently described, so breeding details for it are genuinely sparse. The expectations below follow the consistent pattern across the genus rather than direct observation of this species.
Melanotaenia rainbowfishes spawn over many days, a female depositing a few small, adhesive eggs at a time among fine-leaved vegetation or, in captivity, over spawning mops; the eggs hang from the medium by fine filaments. Incubation in the genus runs on the order of a week or more at warm temperatures. The fry are tiny and surface-oriented at first, and the adults give no care and will eat both eggs and fry. Anyone breeding this species would be working from genus-level husbandry, not an established protocol.
In the aquarium
Melanotaenia wokamensis is noted as having aquarium potential, but it is a recently described species from a single remote island system and is essentially absent from the ornamental trade; it is not an established hobby fish. As such, husbandry recommendations are necessarily generic, extrapolated from closely related and better-known Melanotaenia rather than from experience with this species.
On that basis it should behave like other small rainbowfishes: active, peaceful, and happiest in a group, with open swimming space, some planting, and warm, well-filtered water. Its home in limestone-channel pools points to neutral-to-slightly-alkaline, warm conditions rather than soft, acidic water. Since no water-chemistry figures were recorded at the type locality, a keeper would do well to favour stable, moderately hard, neutral water and treat published parameters for related Aru and New Guinea rainbowfishes as the best available guide.
Conservation
Melanotaenia wokamensis is assessed as Least Concern (LC) on the IUCN Red List, with the species page indicating an assessment carried out in December 2019. The Least Concern listing reflects that, although the species is narrowly distributed, its forest-stream habitat on Wokam Island is not currently considered to be under acute or widespread threat.
Even so, the species is known from only three tributaries of a single drainage on one island, and that kind of extreme localisation always carries risk: a fish confined to one small system has little buffer against habitat disturbance, pollution, or introduced non-native fishes. There is no sign of significant collection for the aquarium trade, and the remoteness of the Aru Islands offers some natural protection. Its long-term security rests on the Wokam Island rainforest catchment staying intact.