Pethia nigripinnis

Pethia: the generic vernacular name for small cyprinids in the Sinhala language.

nigripinnis: from the Latin niger, meaning 'black', and pinna, meaning 'fins', in reference to the black fins in males.

Type locality is Kalindhi stream, a tributary of the Kabini River in Wayanad District, Kerala state, southwestern India, with an additional population known from Kakkan Halla in the Moyar River system, Nilgiri Hills region, Tamil Nadu state.

It therefore appears endemic to the southern Western Ghats mountains.

Inhabits cool, flowing hill streams. Such headwaters are typically well-oxygenated with clear water, substrates comprising gravel, rocks, boulders and patches of leaf litter, with a rich biofilm carpeting solid surfaces.

Habitats are likely to vary depending on locality and time of year with two annual monsoons causing increases in water depth, flow and turbidity in many rivers draining the Western Ghats.

At one locality in the Kalindhi drainage the water was clear, 1 m at its deepest point and flowing either side of a small check dam, below which the flow was stronger though still not particularly fast.

The substrate was composed of rocks and cobbles with a thick layer of fine silt and sand above the dam.

There were no aquatic plants but marginal grasses and shrubs were growing to the margins with some submerged roots protruding into the water.

No specimens of P. nigripinnis were collected in the faster flow below the dam, and males were observed to form small territories rather than schooling together.

Sympatric species were Haludaria fasciata, Pethia conchonius, Puntius bimaculatus, Barilius gatensis, Danio rerio, Salmostoma acinaces, Mesonoemacheilus guentheri, Mystus montanus, Bhavania australis, Channa gachua, Lepidocephalichthys thermalis, and Aplocheilus lineatus.

At a second locality the habitat comprised a small creek flowing through heavy woodland. The water was again shallow and substrate composed of cobbles, silt, and leaf litter.

Aquatic vegetation was absent though there were some submerged root tangles along the banks and overhanging bamboo fronds, while the water was several degrees cooler than the air.

Males were again collected singly and formed small territories among the roots and leaf litter, while females were observed to form small groups of 2-3 individuals.

Other species collected were Pethia conchonius, Longischistura striata, Channa gachua, and Aplocheilus lineatus.

Thanks to Rahul Kumar.

Base dimensions of at least 90 ∗ 30 cm36 ∗ 12 in or equivalent are required with larger quarters required if you wish to keep more than a single male (see 'Behaviour and Compatibility').

Displays its best colouration under dim lighting and should look particularly effective in a heavily-planted arrangement with a darkish substrate, or a set-up designed to resemble a flowing river or stream with a substrate of variably-sized rocks and gravel and some larger, water-worn boulders.

This could be further furnished with driftwood branches and plants such as Microsorum, Bolbitis, or Anubias spp. which can be grown attached to the décor.

Since it naturally inhabits running water this species should never be added to a biologically immature set-up as it requires stable water conditions, and weekly water changes of 30-50 % aquarium volume should be considered mandatory.

Wild fish are probably foragers feeding on diatoms, algae, organic detritus, small insects, worms, crustaceans, and other zooplankton.

In the aquarium it's easily-fed but the best condition and colours offer regular meals of small live and frozen foods such as bloodworm, Daphnia, and Artemia, alongside good quality dried flakes and granules, at least some of which should include additional plant or algal content.

Relatively peaceful but unlikely to make an good choice for the general community aquarium due to its preference for cooler temperatures.

It will probably do best when maintained alone or with comparably-sized species that enjoy similar conditions.

Although gregarious it’s a shoaling rather than schooling fish and a distinct pecking order will form in the confines of an aquarium, meaning it must be decorated in such a way that sufficient broken lines of sight are provided for weaker individuals to seek respite.

In addition rival males will exhibit some interesting sparring behaviour and better colouration in the presence of conspecific rivals, although they do require a significant amount of room with a single territory measuring around 60 square cm.

Adult males are noticeably slimmer than females and significantly more colourful, especially during the spawning season.

When in good condition the dorsal, ventral, and anal fins are deep black, and caudal-fin bright red in males, whereas in females all fins are hyaline.

Not yet achieved in aquaria as far as we know, but notes for related species are as follows:

Like most small cyprinids Pethia spp. are egg-scattering free spawners exhibiting no parental care.

When in good condition they will spawn often and in a mature aquarium it's possible that small numbers of fry may start to appear without intervention.

However if you want to maximise yield a more controlled approach is required.

The adult group can still be conditioned together but a smaller aquarium should also be set up and filled with mature water.

This should be very dimly lit and the base covered with some kind of mesh of a large enough grade so that the eggs can fall through but small enough so that the adults cannot reach them. The widely available plastic 'grass'-type matting can also be used and works well, as does a layer of glass marbles.

Alternatively filling much of the tank with a fine-leaved plant such as Taxiphyllum spp. or spawning mops can also return decent results.

The water itself should be of slightly acidic to neutral pH with a temperature towards the upper end of the range suggested above, and an air-powered sponge filter or air stone(s) should also be included to provide oxygenation and water movement.

When the adults are well-conditioned and the females appear gravid one or two pairs should then be introduced, and spawning should take place the following morning.

An alternative is to spawn the fish in a group with half a dozen specimens of each sex being a good number, although a larger aquarium may be necessary.

In either situation the adults will probably eat the eggs given the chance and should be removed as soon as any are noticed.

These should hatch in 24 - 48 hours with the fry free swimming around 24 hours later.

They should be fed on an infusoria-grade food for the first few days until large enough to accept microworm, Artemia nauplii, or suchlike.

This species is not currently in the aquarium trade but has been maintained by a handful of private collectors.

It was formerly included in the Puntius conchonius 'group' of closely-related species alongside P. ater, P. bandula, P. conchonius, P. cumingii, P. didi, P. erythromycter, P. gelius, P. khugae, P. macrogramma, P. manipurensis, P. meingangbii, P. nankyweensis, P. nigrofasciatus, P. padamya, P. phutunio, P. punctatus, P. reval, P. shalynius, P. stoliczkanus, P. thelys, P. tiantian, and P. ticto, but all of these were moved to the new genus Pethia by Pethiyagoda et al. (2012), as were P. melanomaculata, P. pookodensis, P. muvattupuzhaensis, P. ornatus, and P. yuensis.

Pethia species are defined by the following combination of characters: rostral barbels absent; maxillary barbels minute or absent; possession of a stiff, serrated last unbranched dorsal-fin ray; presence of a black blotch on the caudal peduncle, and frequently, black blotches, spots or bars on the side of the body; infraorbital 3 deep and partially overlapping the preoperculum.

P. nigripinnis can be told apart from congeners by the following combination of characters: barbels absent; last unbranched dorsal ray serrated; 20–21 scales in lateral series; lateral line incomplete with 3–5 pored scales; dorsal, anal, pelvic, and pectoral fins black in adult males; colour pattern comprising a black humeral spot on the 3rd or 4th lateral-line scale and a larger posterior marking on the 18th and 19th scales which appears as a band forming a ring around the caudal peduncle; 2 scales between the posterior marking and hypural notch.

The genus Puntius was viewed as a polyphyletic catch-all containing over 100 species of small to mid-sized cyprinid for a number of years until Pethiyagoda et al. (2012) published a partial review covering South Asian members.

The majority of sub-Himalayan Puntius species were reclassified and new genera Dawkinsia, Dravidia, and Pethia erected to accomodate some of them, with the remainder either retained in Puntius or moved to the existing Systomus assemblage, though the definition of the latter was altered meaning some Southeast Asian species formerly placed there are no longer members.

It subsequently became clear that the name Dravidia was preoccupied by a genus of flesh fly, therefore the replacement name Haludaria was made available by Pethiyagoda (2013).

No species from Indochina, China, or Indonesia were included in the study meaning a significant number of former Puntius are currently classed as incertae sedis, i.e., of uncertain taxonomic placement, and this also applies to a number of South Asian species of unresolved status.

They’re perhaps best referred to as ‘Puntius‘ for the time being whereby the genus name is surrounded by quotation marks to denote its questionable usage, and that is the convention used here on SF at the moment.