Taxonomy & naming
Puntius stigma was described by Achille Valenciennes in 1844 as Leuciscus stigma — at a time when Leuciscus served as a broad catch-all for small freshwater cyprinids throughout the Northern Hemisphere and South Asia alike. The combination was subsequently moved into Puntius, which itself was long used as an equally broad container for the barbs of South and Southeast Asia. Valenciennes named the type from peninsular India; later taxonomic notes have associated the type locality with the Manimala River in the Western Ghats region of South India.
The 2012 revision by Pethiyagoda and colleagues restructured the old Puntius aggregate, erecting several new genera for Southeast Asian and Sri Lankan lineages. Puntius stigma was retained within Puntius sensu stricto, which under that revision encompasses the barbs of the Indian subcontinent that share the diagnostic absence of barbels and a specific suite of osteological characters. The Catalog of Fishes (Eschmeyer, CAS) — the authority for valid names followed here — records the combination as Puntius stigma (Valenciennes, 1844), with the parenthetical indicating that the species has been moved from its original genus.
Morphology
Puntius stigma is a slender, moderately deep-bodied barb reaching about 3.5 in in standard length, though many individuals in lowland habitats are encountered at 2–3 in. The most conspicuous diagnostic character is a large, deep black blotch situated at the base of the dorsal fin, on approximately the fourth and fifth soft rays — the feature that gives the species its name. There are no barbels, which places it firmly within the barbel-less Puntius sensu stricto.
The lateral-line scale count is 22–23, a useful meristic for distinguishing it from related species in the Indian assemblage. Body colouration is otherwise relatively plain: a silvery to brassy background without prominent banding, allowing the dark dorsal blotch to stand out conspicuously. Detailed pigmentation notes from wild specimens are sparse in the accessible literature.
Habitat
The species inhabits a range of lowland and sub-montane freshwater environments across peninsular India, from rivers and streams of the Western Ghats through to ponds, pools, ditches, rice fields, and irrigation channels of the Bengal lowlands. It is recorded as a benthopelagic fish tolerant of slow-flowing to moderately current waters. The broad habitat range — spanning both hill-stream margins and lowland agricultural drainage — suggests considerable ecological flexibility.
FishBase records a mean temperature of around 77 °F and a pH near neutral (7) with soft water (approximately 5 dGH) for this species. The South Indian and Western Ghats populations may encounter cooler, faster, better-oxygenated conditions than the Bengal lowland populations, which live in warm, often organically enriched water. Both conditions appear to be tolerated.
Feeding
Puntius stigma is an omnivore in the broad sense typical of South Asian barbs. Its diet in the wild encompasses plankton, filamentous algae, aquatic insect larvae, and small invertebrates, along with organic detritus picked from the substrate and water column. This opportunistic feeding strategy suits a species occupying habitats as varied as montane river edges and rice-field drainage ditches.
In captivity it is undemanding and accepts good-quality flake and pellet foods, supplemented with live or frozen invertebrates and vegetable matter. As with other small Puntius, variety in the diet helps maintain condition and colouration.
Mating
Like virtually all barbs, Puntius stigma is an egg-scattering, non-guarding spawner. Spawning behaviour follows the typical Puntius pattern: a driving male pursues a ripe female through fine-leaved vegetation or over gravel substrate, pressing against her flanks and releasing eggs and milt together in short bursts. There is no nest, no bubble-nest, and no territorial defence sustained beyond the moment of spawning itself.
No pair bond is formed, and neither parent takes any interest in the eggs after fertilisation. In lowland populations connected to open ponds and ditches, seasonal water-level changes and temperature shifts may act as spawning cues, concentrating adults into suitable areas.
Breeding
Breeding in Puntius stigma, like other members of the genus, involves the scattering of adhesive eggs over fine-leaved aquatic plants, among roots, or onto gravel — wherever the eggs can lodge out of strong current. The literature notes that the species requires clear water, moderate current, and good oxygenation for successful spawning, which aligns with the conditions of its native river and stream habitats.
Fecundity data are not reported in the accessible sources. In an aquarium context, the approach parallels that used for other small Indian barbs: a shallow, well-oxygenated spawning tank, fine-leaved plants or a spawning mop, and the removal of adults after spawning to prevent egg predation. The adults give no parental care and will consume their own eggs if left with them.
In the aquarium
Puntius stigma is an established, if modestly circulated, aquarium barb, documented particularly among ornamental-fish keepers in coastal West Bengal where local collection and trade sustain interest in native species. It is not among the high-profile Indian barbs of the wider trade, but it is kept and bred by enthusiasts of South Asian cyprinids.
It suits a moderately sized, well-filtered aquarium with neutral to slightly acidic, soft water kept around 75–79 °F. As a shoaling species it should be kept in groups, which suppresses skittishness and makes for more natural behaviour. Compatible tankmates are other active, similarly sized South Asian cyprinids. The absence of barbels means it will not compete effectively with more aggressive bottom feeders for food, so target feeding may be needed in mixed tanks.
Conservation
Puntius stigma has not been formally evaluated by the IUCN Red List; its conservation status is therefore Not Evaluated (NE). This is a common situation for the many smaller, lesser-studied members of the Indian Puntius assemblage, where taxonomic complexity and survey gaps have kept several species outside formal assessment cycles.
The species' broad lowland distribution — spanning rivers, ponds, and agricultural waterways from the Western Ghats to Bengal — suggests it is not immediately threatened at a range-wide level. However, the freshwaters of peninsular India face serious ongoing pressures: sand extraction, dam construction, water extraction for irrigation, agricultural runoff, and pollution of lowland waterbodies. Species connected to the Western Ghats in particular occupy one of the world's biodiversity hotspots under mounting land-use pressure. A formal assessment would help clarify the current population trajectory.