Taxonomy & naming
Pethia shalynius was first described by Yazdani and Talukdar in 1975, originally placed in the broadly defined genus Puntius — the taxonomic catch-all that once encompassed the great majority of South and Southeast Asian barbs. The species was carried as Puntius shalynius in older literature for decades until the landmark 2012 revision by Pethiyagoda et al. reorganised the South Asian barb fauna, erecting several new genera on the basis of shared morphological characters. The new genus Pethia was erected to receive a cluster of small, mainly Indian-subcontinent barbs, and shalynius was transferred accordingly; the current valid combination is Pethia shalynius (Yazdani & Talukdar, 1975), with the parenthetical authority marking the move out of the original genus.
The Catalog of Fishes (Eschmeyer, CAS) is the governing authority for valid names and records the placement in Pethia. The genus now comprises several dozen species of small, often brightly marked barbs found across peninsular India, Sri Lanka, and parts of northeastern India — a group previously obscured within the old Puntius aggregate.
The species epithet shalynius is a vernacular-derived name referencing the local Khasi name for the fish; it gives rise to the common trade name Shalyni barb. The fish is also known locally as Phabourga.
Morphology
Pethia shalynius is a small, moderately deep-bodied barb with a typical cyprinid profile — laterally compressed, with a relatively high back and a bluntly rounded snout. FishBase records a maximum total length of 2.5 in, with Seriously Fish noting standard lengths of 2 in for wild adults; it is a compact species well suited to the shallow, rocky hill-stream habitat it occupies.
Sexual dimorphism is evident: males are noticeably smaller and slimmer than females and display more intense colouration, while females become visibly fuller through the abdomen when gravid. Detailed coloration data for live specimens is sparse in the available literature, as the species is infrequently observed or photographed in hobbyist settings, but it shares the general Pethia pattern of a silvery to golden-olive body with darker markings.
Habitat
Pethia shalynius is endemic to the highlands of Meghalaya, northeastern India, where it is known from a restricted number of localities in the Khasi Hills and Jaintia Hills. The type locality is Barapani Lake (also called Umiam Lake), situated approximately 12 mi north of Shillong at an elevation of around 1,328 ft. Wild populations have been recorded in streams and minor tributaries at elevations above 1,656 ft — cool, fast-flowing, clear waters with rocky, boulder-strewn and cobble substrates characteristic of the upland drainages of this region. Spawning has also been observed in association with rice paddies near the Seinpoh stream, Meghalaya.
The species is also recorded from ponds and small lakes with muddy substrates, indicating some flexibility in habitat use, though its core range is the cool, well-oxygenated hill streams. Water conditions at these elevations are cool and near-neutral: Seriously Fish records temperatures of 61–75 °F, pH 6.0–7.5, and hardness in the range of 36–215 ppm — reflecting the varied geology of the Meghalayan highlands. These cool temperatures are an important constraint for aquarium keeping.
Feeding
Pethia shalynius is an omnivore with a diet reflecting both the benthopelagic and open-water resources of its hill-stream habitat. Seriously Fish documents the species feeding on diatoms, algae, and detritus scraped from rocky substrates, as well as small invertebrates including insects, worms, crustaceans, and zooplankton. This broad dietary range is typical of small hill-stream barbs that must exploit diverse food resources across seasons in oligotrophic upland drainages.
In the aquarium, the species would be expected to accept a wide range of prepared and live foods in keeping with its omnivorous habits — small pellets and flake supplemented with live or frozen invertebrates such as daphnia and bloodworm, and some algae-based foods to reflect the grazing component of its wild diet.
Mating
Like all barbs, Pethia shalynius is an egg-scattering, non-guarding spawner with no sustained pair bond and no nest construction. Courtship follows the typical barb pattern in which a driving male pursues a gravid female through vegetation or over the substrate, the pair making brief contact as eggs and milt are released simultaneously into the water column.
Wild spawning is seasonal: a breeding study (Wiley Online Library, Aquaculture Research) documents spawning from May through September, rarely extending into October — coinciding with the monsoon and post-monsoon season in Meghalaya. The species has notably low fecundity compared to many barbs, a biological trait consistent with its restricted population size and that may compound conservation concerns.
Breeding
In the wild, Pethia shalynius spawns once per year between May and September, with spawning events recorded near rice paddies adjoining Meghalayan hill streams (Wiley Online Library, Aquaculture Research). The breeding mode is egg-scattering: adhesive eggs are deposited over fine-leaved plants, roots, or among substrate material, and no parental care is provided. Adults give no attention to eggs or larvae after spawning, and cannibalism of eggs is likely as with most barbs.
The species' low fecundity — notable among cyprinids — means that recruitment into wild populations is limited, making each successful cohort significant for population continuity. For aquarium breeding, cool water temperatures matching the highland habitat (61–72 °F) would be a prerequisite; the spawning tank should replicate the cool, well-oxygenated conditions of Meghalayan hill streams. The combination of restricted natural distribution, low fecundity, and rarity in the aquarium trade means that captive-bred stock is essentially absent from commerce.
In the aquarium
Pethia shalynius is rarely, if ever, available in the mainstream aquarium trade and is not a well-known hobbyist species. Seriously Fish notes that it is not well-established in the trade, and most aquarists are unlikely to encounter it outside of specialist collectors or occasional import of wild-caught fish.
For those who do keep it, the species requires cool, well-oxygenated water reflecting its high-altitude hill-stream origins: temperatures of 61–72 °F, pH 6.0–7.5, and moderate hardness. A strong current with good filtration, and a rocky substrate to mimic the cobble-and-boulder streams of the Khasi Hills, would best suit the fish. As a schooling species, it should be kept in groups. Warm standard community temperatures typical of most tropical aquaria are likely too high for long-term health.
Conservation
Pethia shalynius is assessed as Vulnerable (VU) on the IUCN Red List, with the assessment dated 18 March 2010. The basis for this status is its highly restricted natural range — confined to a small number of localities in the Khasi and Jaintia hills of Meghalaya — combined with ongoing and increasing industrial activity that threatens the integrity of its hill-stream habitats. The Indian Journal of Fisheries (conservation assessment) and multiple secondary sources confirm the Vulnerable categorisation, emphasising that the species' restricted distribution makes it particularly sensitive to local habitat loss.
Threats include industrial development, potential water extraction, and the degradation of upland stream catchments in Meghalaya. The species' documented low fecundity amplifies these risks: populations cannot rapidly recover from perturbation. The wild spawning habitat in rice-paddy-adjacent streams near Seinpoh is itself vulnerable to agricultural intensification. Pethia shalynius has no significant presence in the aquarium trade, which, while eliminating collection pressure, also means that no captive safety-net population exists. Conservation of this barb depends entirely on the protection of its native Meghalayan highland watershed.