Taxonomy & naming
Puntius nigronotus was described by Mathews Plamoottil in a 2014 paper published in the Journal of Research in Biology (volume 4, issue 8, pp. 1581–1588), with the formal species publication dated 2015. The type locality is the Mananthavady River, Wayanad district, Kerala, India — a headwater stream in the southern Western Ghats. The species is placed in Puntius sensu stricto, the residual genus retained for a set of South Asian barbs that were not reassigned when Pethiyagoda et al. (2012) split the old catch-all Puntius into multiple genera including Dawkinsia, Pethia, Systomus, and others. Under the Catalog of Fishes (Eschmeyer, CAS), the valid combination remains Puntius nigronotus Plamoottil, 2015.
The parenthetical authority notation is absent here because Plamoottil described the species directly in Puntius and the combination has not been changed. The species epithet is composed of the Latin roots nigra (black) and notus (back), a direct reference to the blackish dorsal colouration that distinguishes it from its congeners.
Morphology
FishBase records a maximum total length of 4 in for this species, placing it among the mid-sized representatives of Indian Puntius. The body is fusiform and laterally compressed, as is typical of the genus. The dorsal surface is distinctly blackish — the character that gave the species both its scientific name and its common name. A row of tiny black dots marks the dorsal fin, which carries 9 branched rays; the anal fin has 6 branched rays. The lateral line is complete with 27 scales.
Beyond these meristic and colouration details recorded in the original description, detailed information on fin colouration, scale patterning, and secondary sexual characters is not well documented in accessible literature. The species is benthopelagic in habit according to FishBase.
Habitat
Puntius nigronotus is known from the Mananthavady River in Wayanad district, which lies at high altitude in the southern Western Ghats of Kerala. Wayanad is a hilly district ranging from roughly 700 to over 2,100 metres in elevation, and its river systems carry cool, clean, fast-moving water characteristic of Western Ghats upland streams. These habitats are typically well-oxygenated, with near-neutral to slightly acidic pH and low to moderate hardness reflecting the lateritic and gneissic geology of the region.
No specific water-chemistry measurements have been published for the collection locality. Based on the known ecology of co-occurring Western Ghats hill-stream barbs and the altitude and character of the Mananthavady drainage, the species likely tolerates — and probably prefers — cool, clear, flowing conditions rather than warm, still water.
Feeding
No dedicated feeding studies exist for Puntius nigronotus. By analogy with congeners inhabiting similar Western Ghats hill-stream environments, it is likely an opportunistic omnivore taking small invertebrates (insect larvae, aquatic worms), algal biofilms scraped from rock surfaces, and fine organic detritus — the typical diet of small barbs in fast-flowing upland streams.
Data are sparse; any specific dietary claims beyond this would be speculative. In captivity, Western Ghats barbs of similar size generally accept a range of small live and frozen foods along with good-quality dry diets.
Mating
No spawning observations for Puntius nigronotus have been published. Like all barbs, it is an egg-scattering, non-guarding spawner. In the typical barb mating pattern, a driving male pursues a gravid female through vegetation or over the substrate; the pair presses together briefly and releases eggs and milt simultaneously. No pair bond is formed and no territory is held beyond the momentary act of spawning.
Cortship activity in Western Ghats barbs is often seasonal, coinciding with the onset of the monsoon and its associated changes in water temperature, flow, and chemistry. There is no nest construction and no parental care of any kind.
Breeding
Captive breeding of Puntius nigronotus has not been documented in the accessible hobbyist or scientific literature. The species is not established in the ornamental trade and is known almost entirely from wild-caught specimens from its type locality.
In principle, the breeding approach for comparable small Western Ghats barbs — a separate, cool, well-oxygenated spawning tank with fine-leaved plants or a spawning mop, slightly acidic to neutral water, and removal of adults after spawning to protect the adhesive eggs from being consumed — would be a reasonable starting point. Egg-hatching time and larval development are undocumented for this species.
In the aquarium
Puntius nigronotus is not an established aquarium fish. It has not appeared in mainstream trade listings, and no husbandry accounts from hobbyists are in circulation. Its restricted endemic range in high-altitude Wayanad streams and the absence of any captive-breeding programme mean that wild specimens would be difficult to source even where collection and export were legally permitted.
For aquarists who might obtain specimens through scientific or specialist channels, the needs of comparable Western Ghats hill-stream barbs suggest cool (roughly 64–75 °F), clean, well-aerated water with steady flow, near-neutral pH, and soft to moderately hard chemistry. A spacious tank with a current, smooth substrate, and some cover would be appropriate. The species' ecology and modest maximum size suggest it would behave as a social shoaler.
Conservation
Puntius nigronotus has not been assessed by the IUCN Red List; its status is Not Evaluated (NE). The species was described only in 2014–2015 from a single river system in Wayanad district, Kerala, making it a highly range-restricted endemic whose conservation standing is unknown.
The Western Ghats is a globally recognised biodiversity hotspot under significant pressure from agricultural expansion, dam construction, water extraction, and pollution. Several other endemic hill-stream barbs from Kerala and neighbouring states have been found to have small, fragmented populations vulnerable to local extinction. Without a formal assessment or targeted surveys, the population size and trend of Puntius nigronotus remain unknown. Its single known locality in the Mananthavady drainage of Wayanad underscores the need for dedicated fieldwork and eventual Red List evaluation.