Epalzeorhynchos munense (SMITH, 1934)

SynonymsTop ↑

Labeo munensis Smith, 1934; Epalzeorhynchus munensis (Smith, 1934)

Etymology

Epalzeorhynchos: From Epalzeo-, which has an unconfirmed derivation and meaning but is often reported incorrectly to denote ‘curative’ (it may actually mean ‘horn’ in reference to a cone-shaped protuberance on the snout of Epalzeorhynchos spp.), and the Ancient Greek ρυνχος (rhynchos), meaning ‘snout, beak’.

munense: named for the Menam Mun River in eastern Thailand, from which the type series was collected.

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

Type locality is given as “Thailand: Menam Mun at Tha Chang, East of Korat”. Both the type series and the fish in our image were collected from the Mun but it has been recorded from some other tributaries of the middle Mekong in both Thailand and Laos. It’s unclear whether a record from the Tonlé Sap lake/river system is correct or refers to the congener E. frenatum, so it may occur in Cambodia as well.

Habitat

Unconfirmed. Other members of the genus tend to be found in flowing rivers and streams for most of the year but are known to move into seasonally inundated floodplains or forested areas during the wet season.

Maximum Standard Length

100 – 120 mm.

Aquarium SizeTop ↑

An aquarium with base measurements of 120 ∗ 45 cm should be the smallest considered, with larger quarters necessary for a group.

Maintenance

Provided sufficient cover is available this species is relatively unfussy in terms of décor, and should not harm softer-leaved plants. However it will thrive in a set-up designed to resemble a flowing river with a substrate of variably-sized rocks, gravel and some larger, water-worn boulders.

This can be further furnished with driftwood roots and branches plus aquatic plants from genera such as Microsorum, Bolbitis or Anubias which can be grown attached to the décor. Bright lighting will promote the growth of algae upon which the fish will graze.

Like many fishes that naturally inhabit running water it’s quite intolerant to the accumulation of organic wastes and does best if there is a high level of dissolved oxygen and moderate water movement.

Water Conditions

Temperature: 20 – 26 °C

pH: 6.5 – 7.5

Hardness: 36 – 268 ppm

Diet

Primarily an aufwuchs grazer feeding on algae, small crustaceans, insect larvae, etc., and for it to develop its best colours and condition it should be offered regular meals of small live and frozen foods such as chironomid larvae (bloodworm), Daphnia and Artemia along with good quality dried flakes, granules and fresh plant material.

Shelled peas, cucumber, blanched courgette, spinach and chopped fruit all make good additions to the menu. Once settled it will often ascend into midwater to feed and in a rivertank-style set-up as described above will often be seen browsing the biofilm that tends to form on the rockwork.

Behaviour and CompatibilityTop ↑

Probably similar to others in the genus, meaning that while small specimens tend to hide away much of the time they become increasingly territorial as they grow and can display particularly high levels of aggression towards similar-looking species.

Some individuals may be more belligerent than others and there exist reports of apparent alliances with other species such as Chromobotia macracanthus. We’re unsure if these behavioural differences are indicative of gender but at any rate loaches from the genera Chromobotia, Botia, Syncrossus and Yasuhikotakia do seem to be left in peace by Epalzeorhynchos species whereas congenerics and members of Crossocheilus, Garra and Gyrinocheilus, for example, tend to be attacked constantly. Please note that in terms of the loaches not all may be housed together and proper research is essential.

Other bottom-dwelling fishes including cichlids and most catfish are best avoided as they may too be picked on. For the upper levels choose robust, active, schooling cyprinids. Ideally the Epalzeorhynchos should be the final addition to the tank in order to avoid it claiming ownership of the entire space.

This species probably lives a solitary lifestyle and in nature would probably have only come into contact with others of its own kind infrequently and during the spawning season. These instincts heighten as the fish get older and we therefore recommend it be kept singly in the majority of cases. In a very large tank with lots of cover a cohabitation attempt might be possible but each individual is likely to require a territory with a diameter of at least a metre.

Sexual Dimorphism

Sexually mature females should be noticeably thicker-bodied than males.

Reproduction

This species has neither been bred in aquaria nor produced commercially as far as we know, though others in the genus are farmed for the aquarium trade using hormones.

NotesTop ↑

This species does not appear to be in the aquarium hobby at time of writing though it may have been in the past, when exports of wild Epalzeorhynchos spp. still took place.

Most members of the genus were formerly regarded as Labeo spp. and are thus referred to as such in older literature. According to Rainboth (1996) they are characterised by absence of a dorsal spine, possession of 10-13 branched dorsal fin rays, a thin membrane connecting the upper and lower lips and rigid, freely moveable rostral lobes.

Epalzeorhynchos itself has undergone some quite recent changes with a handful of species having been reassigned to Crossocheilus and E. bicornis moved to the new genus Akrokolioplax (Zhang and Kottelat, 2006). The latter was erected on the basis of differences in oral morphology and the position/structure of the so-called ‘rostral lateral lobes’ on the snout, a feature unique to these two genera.

Of the remaining species E. frenatum and E. kalopterus have been mainstays of the aquarium hobby for many years while the identity of E. munense now appears established. Smith (1934) described it as possessing a brown body, black dorsal fin edged in white and a white caudal fin, with type locality given as the Mun/Moon river, a tributary of the Mekong in eastern Thailand.

Fish collected since are similar in appearance to E. bicolor and E. frenatum, but distinguishable by a unique combination of black head, body and anal-fin, red caudal and dorsal fins, and black margins on the pelvic and pectoral fins (Kottelat, 1998).

These features have been recognised by several authors who also noted that preserved specimens tended to lose the red pigmentation in the fins after three months in alcohol and that the holotype of E. munense had been collected eight years prior to its description, thus meaning live colouration was not included. The possibility that E. frenatum and E. munense have hybridised in aquaculture at some point cannot be discounted.

Some SF forum members keep/have kept a fish which closely resembles E. bicolor but possesses a white caudal fin and is most often found among batches of E. frenatum. It is unclear whether this is a genetic sport among farm-bred fish or a potentially undescribed species but certainly the white pigmentation does not alter with age or conditioning.

There is also a commercially-produced anerythristic (lacking red pigment) mutation of E. frenatum that has pale yellowish fins and has sometimes been misidentified as E. munense. A recent introduction to the hobby is an albino form of E. bicolor but this has yet to achieve the same degree of popularity as the ubiquitous albino E. frenatum.

References

1. Smith, H. M., 1934 - Journal of the Siam Society, Natural History Supplement 9(3): 287-325
   Contributions to the ichthyology of Siam.
2. Kottelat, M., 1998 - Ichthyological Exploration of Freshwaters 9(1): 1-128
   Fishes of the Nam Theun and Xe Bangfai basins, Laos, with diagnoses of twenty-two new species (Teleostei: Cyprinidae, Balitoridae, Cobitidae, Coiidae and Odontobutidae).
3. Kottelat, M., 2013 - The Raffles Bulletin of Zoology Supplement 27: 1-663
   The fishes of the inland waters of southeast Asia: a catalogue and core bibiography of the fishes known to occur in freshwaters, mangroves and estuaries.
4. Rainboth, W. J., 1996 - FAO, Rome: 1-265
   Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes.
5. Yang, J.-X. and R. Winterbottom , 1998 - Copeia 1998(1): 48-63
   Phylogeny and zoogeography of the cyprinid genus Epalzeorhynchos Bleeker (Cyprinidae: Ostariophysi).
6. Zhang, E. and M. Kottelat, 2006 - Zootaxa 1225: 21-30
   Akrokolioplax, a new genus of Southeast Asian labeonine fishes (Telesotei: Cyprinidae).