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Puntius denisonii (DAY, 1865)

Red-line Torpedo Barb

SynonymsTop ↑

Labeo denisonii Day, 1865; Barbus denisonii (Day, 1865); Crossocheilus denisonii (Day, 1865)

Etymology

denisonii: named for Sir William Thomas Denison (1804-1871), governor of Madras, India from 1861-1866.

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

Described from ‘Mundakayam, Travancore, India’, which appears to correspond to the Manimala River near the town of Mundakayam in Kottayam District, Kerala state, southern India, and the species is endemic to Kerala plus the neighbouring state of Karnataka.

It’s modern distribution is highly fragmented with small populations remaining in the Valapatanam, Chaliyar, Kallar, Karyangod, Kuttiyadi, Chandragiri, Sullya, Kuppam, Iritti, Anjarakandipuzha, Bhavani, and Bharatapuzha river systems.

Historical records from the Chalakudy, Periyar, Manimala, and Pamba river systems apparently represent P. chalakkudiensis though the Manimala data may be questionable given it seems to be the type locality of P. denisonii.

In the Achankovil River system it occurs sympatrically, and sometimes syntopically, with P. chalakkudiensis.

Wild stocks may have dwindled by as much as 50% in the last 15 years or so with collection for the aquarium trade largely held responsible although habitats are also being degraded by pollution from agricultural and domestic sources, plus destructive fishing methods involving explosives or organic toxins.

It’s being produced on a commercial basis in Southeast Asia and Eastern Europe though it’s unclear if this has reduced the demand for wild fish.

Habitat

A stream and river-dwelling species most often found in pristine, highly-oxygenated headwaters and upper parts of river basins where it typically congregates in rocky pools with dense riparian vegetation.

It’s supposedly more active at dusk and dawn than during daylight hours.

Maximum Standard Length

90 – 110 mm.

Aquarium SizeTop ↑

Base dimensions of at least 120 ∗ 45 cm or equivalent are required.

Maintenance

Not difficult to keep in a well-maintained set-up, though we recommend aquascaping the tank to resemble a flowing stream or river with a substrate of variably-sized, water-worn rocks, sand, fine gravel and perhaps some small boulders.

This can be further furnished with driftwood roots or branches, and while the majority of aquatic plants will fail to thrive in such surroundings hardy types such as MicrosorumBolbitis or Anubias spp. can be grown attached to the décor.

Since it naturally occurs in pristine habitats it’s intolerant to accumulation of organic pollutants and requires more-or-less spotless water in order to thrive.

Though torrent-like conditions are unnecessary it also does best if there is a high proportion of dissolved oxygen and moderate water movement, and weekly water changes of 30-50% tank volume should be considered routine.

Water Conditions

Temperature15 – 25 °C

pH6.5 – 7.8

Hardness90 – 447 ppm

Diet

A foraging omnivore in nature feeding on a variety of worms, insects, crustaceans, plant material, and other organic debris.

In the aquarium it’s easily-fed but a balanced diet comprising regular meals of small live and frozen foods such as bloodwormDaphnia, and Artemia alongside good quality dried flakes and granules will being about optimal condition and colours.

It’s said that the red pigmentation can be intensified by feeding a diet rich in carotenoids such as astaxanthin.

Behaviour and CompatibilityTop ↑

Relatively peaceful but best kept with other riverine species such as Danio, Devario, Barilius, Garra, plus robust balitorid and nemacheilid loaches.

That said provided its oxygen and temperature requirements can be met it can be mixed with most peaceful fish too large to be considered food.

Reports of aggression may stem from the fact that often only one or two specimens are purchased due to its relatively high price.

It’s a schooling species so 6-10 specimens should be the minimum considered under ideal circumstances.

Maintaining it in such numbers will not only make the fish less prone to bouts of skittishness but result in a more effective, natural looking display, and any aggressive behaviour will normally be contained as individuals concentrate on maintaining hierarchical position within the group.

The similar-looking P. chalakkudiensis is occasionally traded as P. denisonii (see ‘Notes’) and is known to be more belligerent so it’s also possible that misidentification may be partly responsible.

Sexual Dimorphism

Adult females tend to grow a little larger, are heavier-bodied, and a little less colourful than males.

Reproduction

Large numbers are produced for the aquarium hobby in commercial facilities, presumably via stimulation with hormones.

It’s been reported that juveniles are being over-collected from the wild and this appears to be exerting a detrimental impact on its’ conservation status (see ‘Notes’).

In terms of private success at least one report of ‘accidental’ spawning exists, in which a couple of fry were discovered hiding among plants during aquarium maintenance.

A more detailed report was published in the German magazine Aqualog in 2005. In this case a group of 15 adults spawned in soft, acidic water (gH 2-3/pH 5.7), depositing their eggs in a clump of Java moss (Taxiphylum barbieri).

Apparently several of the adults exhibited a colour change with the dorsal surface turning blue, and the event appeared to be triggered by a gradual lowering of the pH via addition of bogwood.

Chester Zoo Aquarium in England have also reported successful breeding, and their theory is that a large group of fish is needed as spawning is hypothesised to occur en masse.

This species has been hybridised with at least one other Puntius species which was presumed to be either ‘P. dunckeri or ‘P. everetti but is actually a member of the genus Dawkinsia (R. Collins, pers. comm.) and such fish are now quite widely available.

NotesTop ↑

This species has undergone a boom in popularity since it was first exported in 1996 and is now traded under various alternative names including ‘Denison’s barb‘, ‘denisoni barb‘, ‘Denison’s flying fox’, ‘rose line shark’, ‘bleeding-eye barb‘, ‘red flash barb’, and ‘Indian flasher barb‘.

In India it’s known locally as ‘Miss Kerala’ and ‘Chorai Kanni’ ( literally ‘bleeding eyes’).

In the 2000s it was the Indian state of Kerala’s most important export but collection of wild fish is now prohibited to an extent.

A 2011 study of its reproductive biology revealed that the sex ratio in wild fish appears skewed in favour of males and that absolute fecundity, i.e., the total number of eggs per female at a given point in time, is relatively low compared with some relatives such as Systomus sarana or Rasbora daniconius. 

Such factors, combined with habitat degradation via pollution or alteration, are likely to have an adverse effect on natural recruitment while affecting population dynamics and potentially leading to a reduced number of individuals in a given population.

In 2011 the ‘closed season’ for collection was June, July, and October, based on the assumpti0n that spawning takes place during these months, but Solomon et al. (2011) demonstrated that breeding occurs from October to March and collection should instead be prohibited between these months in order to adequately protect populations.

On description P. denisonii was initially placed into the genus Labeo but has also been considered a member of both Barbus and Crossocheilus by various authors.

The first specimens exported for the aquarium hobby were collected from the bottom of a waterfall in the Chalakudy River basin, Kerala and identified as P. denisonii based on colour pattern, but were larger and reportedly more boisterous than the fish we now see in the hobby.

For the first few years all fish traded were apparently of this larger type and it was subsequently described as Puntius chalakkudiensis (Menon, Rema Devi & Thobias, 1999), but confusion arose when the latter name was mistakedly assigned to a fish of the genus Dawkinsia by Indian exporters prior to publication.

As a result other members of that group such as D. assimilis have been sold as P. chalakkudiensis at times.

A second, more easily accessible, locality was discovered in 2001 and the fish collected there were found to have a more placid temperament and reach a smaller size in the aquarium.

These turned out to be the true P. denisonii and it’s now among the more iconic species available in the aquarium trade.

It’s since been articificially hybridised with a member of the genus Dawkinsia and a selectively-bred ‘gold’ colour form has also been produced. Both variants are available in the hobby.

P. denisonii can be told apart from P. chalakkudiensis by possession of a subterminal mouth (vs. inferior) and absence of a black marking in the dorsal-fin (vs. presence), plus the anterior red body stripe is also brighter and terminates beneath the centre of the dorsal-fin (vs. duller and terminates beneath or anterior to dorsal-fin origin).

The subspecies P. denisonii ubangii is not considered valid at present.

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).

P. denisonii was retained in Puntius sensu stricto (but see below) was retained in Puntius sensu stricto, of which members are defined by the following combination of characters: adult size usually less than 120 mm SL; maxillary barbels absent or present; rostral barbels absent; 3-4 unbranched and 8 branched dorsal-fin rays; 3 unbranched and 5 branched anal-fin rays; last unbranched dorsal-fin ray weak or strong and unserrated; lateral line complete with 22-28 pored body scales; free uroneural present; gill rakers simple and acuminate (not branched or laminate); no antrorse predorsal spinous ray; post-epiphysial fontanelle usually present (except in P. bimaculatus and P. titteya); 4 supraneurals; infraorbital 3 slender; 5th ceratobranchial narrow; pharyngeal teeth 5 + 3 + 2; 12-14 abdominal and 14-16 caudal vertebrae; colour pattern including a (sometimes faint) blackish spot on the caudal peduncle.

P. chalakkudiensis and P. denisonii differ from all other species in terms of colour pattern and mouth shape, however, and remain in Puntius only because the authors lacked material for DNA and osteological analysis, though they state that both are likely to warrant placement in a different genus in the future.

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.

References

  1. Day, F., 1865 - Proceedings of the Zoological Society of London 1865(1): 286-318
    On the fishes of Cochin, on the Malabar Coast of India. Part II. Anacanthini.
  2. Baby, F., J. Tharian, S. Philip, A. Ali, and R. Raghavan, 2011 - Journal of Threatened Taxa 3(7): 1936-1941
    Checklist of the fishes of the Achankovil forests, Kerala, India with notes on the range extension of an endemic cyprinid Puntius chalakkudiensis.
  3. Menon, A. G. K., K. Rema Devi, and M. P. Thobias , 1999 - Records of the Zoological Survey of India 97(4): 61-63
    Puntius chalakkudiensis, a new colourful species of Puntius (Family: Cyprinidae) fish from Kerala, south India.
  4. Pethiyagoda, R., 2013 - Zootaxa 3646(2): 199
    Haludaria, a replacement generic name for Dravidia (Teleostei: Cyprinidae).
  5. Pethiyagoda, R., M. Meegaskumbura, and K. Maduwage, 2012 - Ichthyological Exploration of Freshwaters 23(1): 69-95
    A synopsis of the South Asian fishes referred to Puntius (Pisces: Cyprinidae).
  6. Raghavan, R., G. Prasad, B. Pereira, P. H. Anvar Ali, and L. Sujarittanonta, 2009 - Aquatic Conservation: Marine and Freshwater Ecosystems 19: 67-74
    ‘Damsel in distress’ - The tale of Miss Kerala, Puntius denisonii (Day), an endemic and endangered cyprinid of the Western Ghats biodiversity hotspot (South India).

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