Taxonomy & naming
Pethia poiensis was described by Shangningam and Vishwanath in 2018, published in Zootaxa 4379(4): 585–593. The type locality is the Challou River, Chindwin Basin, Ukhrul District, Manipur, India. The species belongs to the genus Pethia, which was erected by Pethiyagoda, Meegaskumbura and Maduwage (2012) to receive a cohort of South and Southeast Asian barbs previously lumped within the broadly defined genus Puntius. Pethia poiensis was therefore never formally placed in Puntius; it was assigned to Pethia at the time of its original description.
The Catalog of Fishes (Eschmeyer, CAS) is the authority for valid names. The parenthetical form of the authority — (Shangningam & Vishwanath, 2018) — indicates that the species was not originally described in the genus Pethia, but in practice the species has been treated as Pethia poiensis since its publication. The Chindwin Basin drains westward into Myanmar and joins the Irrawaddy, placing this species at the biogeographic boundary between the Indian subcontinent and mainland Southeast Asia.
Morphology
Pethia poiensis reaches approximately 1.5 in in standard length, placing it among the smaller members of its genus. The most diagnostic characters are an incomplete lateral line with only 7–9 pored scales (rather than the complete line seen in many congeners), the complete absence of barbels, and a lateral-scale count of 19–20 in the main series.
Coloration features two prominent dark marks: a humeral spot situated on the third and fourth scales of the lateral series, and a caudal spot on the sixteenth and seventeenth lateral scales near the base of the tail. A dark stripe runs along the flank between these marks. These pigment patterns, combined with the reduced lateral line and scale formula, distinguish P. poiensis from other Pethia species described from northeast India and the Chindwin drainage.
Habitat
The type locality of Pethia poiensis is the Challou River in the Chindwin Basin, Ukhrul District, Manipur — a hill stream in a region of steep terrain in the Indo-Myanmar hills. FishBase classifies the species as a pelagic freshwater fish of tropical affinity, consistent with the hill-stream biotopes characteristic of upper Chindwin tributaries.
Hill streams draining the Ukhrul highlands typically run clear, fast, and well-oxygenated over rocky or gravelly substrates, with water temperatures that may be cooler than the lowland Chindwin. Beyond the type locality, the precise distribution and preferred microhabitat of P. poiensis within the Chindwin system have not been documented in detail, reflecting the species' recent description and the limited survey effort in remote northeastern Indian river systems.
Feeding
No specific dietary study has been published for Pethia poiensis. By analogy with other small Pethia species from similar hill-stream habitats, the species is presumed to be an opportunistic omnivore, taking small aquatic invertebrates — midge larvae, small crustaceans, and worms — along with algae, diatoms, and particulate organic matter scraped from rock surfaces or collected from the substrate and water column.
In the aquarium, small Pethia of this size class typically accept good-quality micro-pellets and crushed flakes alongside live and frozen foods such as micro-worm, daphnia, and newly hatched brine shrimp. Varied feeding supports condition and colour. Specific data for this species are lacking; recommendations should be treated as informed inference from the genus.
Mating
Like all barbs, Pethia poiensis is an egg-scattering, non-guarding spawner. No courtship or spawning observations specific to this species have been published, but the reproductive mode is consistent across the family. A driving male pursues a gravid female through vegetation, over the substrate, or among rocks in the stream bed, and the pair release eggs and milt together in brief presses.
There is no pair bond, no nest, no bubble-nest, and no form of mouthbrooding. Eggs are adhesive and scatter among fine-leaved plants, into substrate gaps, or over gravel. Adults give no care and will consume eggs given the opportunity. In hill-stream barbs, spawning may be seasonal and linked to monsoon-driven changes in temperature and current.
Breeding
No captive breeding record for Pethia poiensis has been documented in the published literature or in the aquarium hobby, consistent with the species' recent description and limited availability. Based on the biology of closely related small Pethia species from comparable habitats, a soft, slightly acidic to neutral, well-oxygenated spawning setup with fine-leaved plants or a spawning mop over a substrate mesh is likely to be appropriate.
Adults would be expected to scatter a small clutch of adhesive eggs and should be removed after spawning to prevent predation on the eggs. Eggs in similar species hatch in approximately 24–36 hours at appropriate temperatures, with free-swimming larvae appearing a few days later. All such recommendations are inferred from the genus rather than direct observation of P. poiensis.
In the aquarium
Pethia poiensis is not an established aquarium fish. It was described scientifically only in 2018, and no dedicated hobby profile has been published for the species. Like other small hill-stream Pethia from northeast India, it would be expected to require clean, well-oxygenated water with moderate to good current, and water parameters reflecting its native hill-stream habitat — likely near-neutral pH and temperatures on the cooler end of tropical, broadly consistent with the Ukhrul highlands.
Should the species enter the hobby, it would be best kept as a small shoal in a species-appropriate biotope aquarium. Its small adult size of approximately 1.5 in SL makes it suitable for compact setups. Until the species is reliably available in trade and more is known of its specific requirements, aquarium recommendations remain tentative.
Conservation
Pethia poiensis has not been formally assessed by the IUCN Red List, a reflection of how recently it was described rather than any judgment about its status. The species is known only from the Challou River in Ukhrul District, Manipur, and its full range within the Chindwin system is undocumented.
The Chindwin Basin in northeast India faces pressures common to many Indo-Myanmar hill-stream drainages, including agricultural encroachment, forest clearance on steep slopes, sedimentation of headwater streams, and periodic collection of small ornamentals. Given its apparently restricted known range and the ecological sensitivity of hill-stream habitats, precautionary attention to the status of P. poiensis and its water body would be warranted as survey coverage of Manipuri stream fauna improves.