Oreichthys crenuchoides - Drape Fin Barb

Cyprinidae

Possibly endemic to the Buxa (often spelled 'Buxar') Tiger Reserve in West Bengal State, northeast India. This 760km² forested area lies in the sub-division of Alipurduar, Jalpaiguri district and shares its northern boundary with Bhutan. It's home to some of India's most distinguished animals including tiger, elephant, leopard and regal python. The type specimens were collected from the Jorai River, also in West Bengal, although we've seen one shipment labelled with the locality 'Ghoti Ganga River, Cooch Behar district' and Andrew Rao told us it can be collected from a "couple" of rivers so it may have a wider distribution than currently recognised.

Inhabits slow-moving tributaries and minor rivers with dense marginal vegetation and either clear or turbid water.

Around 35 - 45 mm.

A tank measuring 24" x 15" x 12"/60cm x 37.5cm x 30cm/70.8 litres is big enough to house a small group of these.

This species will thrive in a heavily-planted set-up as the multitude of hiding places will provide the sense of security it needs to display natural behaviour. It will also appreciate the dimly-lit conditions towards the bottom of the tank where it will spend most of its time. Use as soft a substrate as possible for the plant species being grown because Oreichthys have miniscule sensory bristles on the lower jaw which are used in foraging the substrate for food. Driftwood branches, floating plants and leaf litter can all be added to lend a more naturalistic feel. This fish will not do well at all under sparsely-furnished or brightly-lit conditions.

It can be a little tricky to acclimatise to aquarium life as it often arrives in poor condition and seems to be rather sensitive to swings in water chemistry. As a result it should not be introduced to biologically immature aquaria and small, regular water changes of around 10% tank volume are the ideal in terms of maintenance.

75 - 82°F/24 - 28°C

6.0 - 7.5

2 - 10°H

It will accept dried foods of a suitable size but should not be fed these exclusively. Daily meals of small live and frozen fare such as Daphnia, Artemia and suchlike will result in the best colouration and encourage the fish to come into breeding condition. A degree of vegetable matter should also be included on the menu; a decent quality dried product containing Spirulina or similar will suffice for this. It is noted as something of a shy, reluctant feeder (see below).

Not really suitable for most community tanks as it has a retiring nature and may be intimidated or outcompeted for food by larger/more boisterous tankmates. Small, peaceful cyprinids such as Trigonostigma or Boraras species make good choices and we suspect it will also do ok with many small South American characins, Otocinclus or pygmy Corydoras catfish. Accommodating it in a biotope-style community of Indian fish is more tricky although suitable species from the Ganges basin include Badis badis , Pangio pangia and Colisa chuna .

Although gregarious by nature it's a shoaling rather than schooling fish which develops a distinct pecking order. Indeed the behaviour between rival males is something to behold with displays involving full extension of the enormous dorsal fin and occasional locking of mouths. It should be maintained in a group of 8 or more but the tank must be of a sufficient size to allow weaker individuals some respite from dominant conspecifics, and decorated in such a way that many broken lines of sight exist. If kept singly, in a very small group or in cramped conditions it can become withdrawn and subdominant fish may be bullied incessantly.

Males tend to grow larger than females, exhibit more colour on the body and fins and develop the magnificent extended dorsal fin that gave rise to the trade name for this species. Sexually mature females are rounder in the belly than males.

Like many small cyprinids this species is an egg-scattering, continuous spawner that exhibits no parental care. That is to say when in good condition and in the presence of both males and females relatively small numbers of eggs will be laid daily. In a properly-furnished aquarium as described above it is therefore possible that small numbers of fry may start to appear without human intervention.

However if you want to increase the yield of fry a slightly more controlled approach is required. The adult group can still be conditioned together but one or more small, say 18" x 12" x 12"/45cm x 30cm x 30cm/42.5 litre, containers should also be set up. Water chemistry parameters ought to be within the values suggested above, the most important factor being that they remain stable. Décor can be very simple; a couple of sinking spawning mops or good-sized clumps of Java moss will give the fish somewhere to deposit their eggs. Filtration is not absolutely necessary although you may wish to include a small air-powered sponge filter bubbling away gently.

One or two pairs of well-conditioned adult fish should then be introduced to each container. It is wise to make the transfer slowly in order to avoid excessive levels of stress but if conditions are to their liking they should begin to spawn the next afternoon or evening. Whether this species eats its eggs or not is unclear although it certainly appears not to actively hunt for them as is the case with many small Puntius and other related species. Once spawning has commenced it should continue sporadically on a daily basis without risk of any undue aggression towards the female(s). Unlike most other cyprinids the female deposits eggs while swimming in an inverted (upside-down) position as in Puntius gelius , P. canius and Trigonostigma species.

A further interesting behaviour noted by Schäfer (2009) when describing the species is the tendency of some sub-ordinate males to maintain a small body size/dorsal fin and take on the general appearance of females. These were observed to display "sneaking" behaviour during the spawning period, but if isolated began to develop the typical extended dorsal fin after around 8 weeks.

The pair(s) can be left in situ for two or three days then removed as the first eggs should hatch by the third day after the initial spawning. The tiny young will survive on their yolk sacs for around 5 more days after which they will require Paramecium or other microscopic food. After 8 days they should be large enough to accept Artemia nauplii/microworm etc. As the days pass additional fry should start to appear from later spawning events. It's best to wait a week or two before starting to perform small water changes in order to avoid unduly shocking the young fish.

This fish is sometimes imported and sold as Oreichthys cosuatis  which has led to considerable confusion as it's now pictured with that name both in published and online literature. It may also be seen on trade lists as Oreichthys sp. 'high fin', O. 'umangii' (a nomen nudum that has only ever been applied to an image of a fish in the book 'Ornamental Aquarium Fish of India' by Kishori Lal Tekriwal and Andrew Arunava Rao and for which no description is known to exist), Puntius 'arunavii' or 'neon highfin barb' (both fabricated trade names). Prior to its description some believed it would turn out not to be a Puntius due to various aspects of its anatomy, and in fact it's easily distinguished from O. cosuatis  and O. parvus by its more rounded head and body shape, larger/more clearly defined dark blotch on the caudal peduncle (absent in O. cosuatis  and much smaller in parvus), no blotch on the anal fin (vs. present), an overall pearly-blue sheen to the body and a more extended dorsal fin in adult males.

It seems certain that new species of Oreichthys will be described in the future as there exist at least four undescribed forms from Myanmar, several from India (including one that's said to originate in the Western Ghats mountain range which is intriguing as the genus was previously thought confined to northeastern parts of the country) and possibly others from Thailand. The described species are quite easy to distinguish from one another as O. cosuatis  exhibits a yellow blotch in the dorsal fin whereas in O. parvus the same fin is coloured red. Several of the undescribed fish have also been sold as O. cosuatis  and telling some of these apart is trickier. One form from the Dibru River in Tinsukia District, Assam state, India is very similar indeed but has a less rounded dorsal fin for example. Other variants from Myanmar differ in fin colour or patterning such as the extent of the dark blotch at the caudal peduncle (this being absent altogether in some).

Members of this genus possess rows of sensory papillae on the snout, cheeks, throat, opercle and interorbital area that are lacking in most other cyprinids but present in a few other genera including Eirmotus, Cyclocheilichthys, Neobarynotus and a handful of Puntius species.

Literature cited

1. www.indianaquariumhobbyist.com
2. www.petfrd.com
3. Tan, H.H. and M. Kottelat. - Raffles Bull. Zool. 56(2):423-433. 2008
   Revision of the cyprinid fish genus Eirmotus, with description of three new species from Sumatra and Borneo.
4. Schäfer, F. 2009 - Ichthyol. Explor. Freshwat. 20(3): 201-211.
   Oreichthys crenuchoides, a new cyprinid from west Bengal, India.