Opsarius infrafasciatus (FOWLER, 1934)

SynonymsTop ↑

Barilius infrafasciatus Fowler, 1934

Etymology

Opsarius: apparently from an Ancient Greek word meaning ‘small fish’.

infrafasciatus: from the Latin infra, meaning ‘below’, and fasciatus, meaning ‘banded’.

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

Currently understood to occur within the Ping river in Thailand, Ataran and Salween drainages in Myanmar and China and tributaries of the Mekong in China.

Type locality is given as ‘Metang River, 35 miles north of Chieng Mai, northern Thailand’, this corresponding to the Mae Tang river in Chiang Mai province, northern Thailand.

Habitat

Typically inhabits headwaters and similar well-oxygenated, low-to-medium gradient, moderate to fast-flowing minor rivers and streams with substrates of gravel, cobbles, larger boulders and exposed bedrock.

It occurs alongside numerous other fish species in the wild with some of those inhabiting the Ataran river including Acanthocobitis pictilis, Botia kubotai, Schistura vinciguerrae, S. robertsi, Garra sp. ‘redtail’, Batasio feruminatus and Mastacembelus armatus as well as some unidentified Devario, Scaphiodonichthys, Tor, Neolissochilus, Garra and Schistura spp.

Maximum Standard Length

70 – 100 mm.

Aquarium SizeTop ↑

Requires a large aquarium with minimum surface area of 120 ∗ 45 cm or equivalent.

Maintenance

The aquarium should ideally be designed to resemble a flowing stream or river with a substrate of variably-sized rocks, sand, fine gravel, and some larger water-worn boulders. This can be further furnished with driftwood roots and branches if you wish but be sure to leave plenty of open swimming space.

While the majority of aquatic plants will fail to thrive in such surroundings hardy genera such as Microsorum, Bolbitis, or Anubias spp. can be grown attached to the décor.

This species is intolerant to the accumulation of organic wastes and requires spotless water at all times in order to thrive. It also does best if there is a high proportion of dissolved oxygen and moderate degree of water movement meaning external filters, powerheads, airstones, etc., should be employed as necessary.

As stable water conditions are obligatory for its well-being this fish should never be added to biologically-immature aquaria, and weekly water changes of 30-50% aquarium volume should be considered mandatory. A tightly-fitting cover is also essential as Opsarius spp. are prodigious jumpers.

Water Conditions

Temperature: 18 – 26 °C

pH: 6.0 – 8.0

Hardness: 36 – 215 ppm

Diet

Opsarius spp. are predominantly surface-feeders preying on aquatic and terrestrial insects in nature, with some small fishes and benthic invertebrates probably taken as well.

In the aquarium good quality dried products can be offered but should be supplemented with regular meals of live and frozen fare such as chironomid larvae (bloodworm), Artemia, chopped earthworms, etc. Drosophila fruit flies and small crickets are also suitable provided they are gut-loaded prior to use.

Behaviour and CompatibilityTop ↑

Unsuitable for the general community due to its environmental requirements, and likely to outcompete or intimidate slow-moving and less bold species at meal times since it is an extremely fast swimmer and vigorous feeder. Much smaller fishes should also be omitted as they may be predated upon.

The best tankmates are similarly-sized, robust, pelagic cyprinids such as Dawkinsia, Barilius or larger Devario and Rasbora spp. while bottom-dwellers could consist of Garra, Crossocheilus, Botia and Schistura spp., for example. Many characids and loricariid catfishes should also work well, but be sure to perform thorough research before purchase.

Although gregarious by nature this is a shoaling rather than schooling species which develops a distinct pecking order and therefore should always be maintained in a group of five or more individuals. If only two or three are purchased the subdominant fish may be bullied incessantly whereas solitary specimens may become aggressive towards similar-looking species.

Sexual Dimorphism

Nuptial male individuals possess visible breeding tubercules on the head and body and are more intensely-coloured than females.

Females also tend to grow a little larger and are thicker-bodied than males, especially when gravid.

Reproduction

Unreported.

NotesTop ↑

This species has previously been considered synonymous with both O. ornatus and O. pulchellus but is currently considered to be distinct following (Tejavej, 2012).

It can be distinguished from congeners by a combination of characters including: small caudal spot present; 36-41 lateral line scales; 6–7 scale rows above lateral line; anal-fin origin located opposite to the 4th-7th branched dorsal-fin ray; head depth 18.3–23.9% SL; rostral and maxillary barbels short or absent; dentary tubercles small.

The generic placement of species currently referred to Opsarius has been open to question since Howes (1980) concluded that the Barilius grouping, within which they were included at the time, was not monophyletic and identified two separate lineages. The first group contained B. barila, the type species, plus B. bendelisis, B. radiolatus, B. vagra, and B. shacra, while the second included all other species, and initially these were referred to the subdivisions ‘group i’ and ‘group ii’ within Barilius itself.

The composition of these groups is confusing since in a later work Howes (1983) included B. evezardi and B. modestus in ‘group i’ whilst omitting B. bendelisis, B. radiolatus, and B. shacra without explicitly stating why.

Rainboth (1991) assigned the members of Howe’s ‘group ii’ to the revalidated generic name Opsarius based on the fact it was the oldest available with ‘group i’ species retaining the name Barilius due to the presence of the type species.

This system has been followed by some subsequent authors, e.g., Tang et al. (2010) and Collins et al. (2012) but not gain wider usage until Kottelat (2013), who included all former Barilius from Southeast Asia in Opsarius.

References

1. Fowler, H. W., 1934 - Proceedings of the Academy of Natural Sciences of Philadelphia v. 86: 67-163
   Zoological results of the third De Schauensee Siamese Expedition, Part I. Fishes.
2. Howes, G. J., 1980 - Bulletin of the British Museum (Natural History) : Zoology series 37(3): 129-198
   The anatomy, phylogeny and classification of bariliine cyprinid fishes.
3. Kottelat, M., 2013 - 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. Liao, T-Y, S. O. Kullander, and F. Fang, 2011 - Journal of Zoological Systematics and Evolutionary Research 49(3): 224-232
   Phylogenetic position of rasborin cyprinids and monophyly of major lineages among the Danioninae, based on morphological characters (Cypriniformes: Cyprinidae).
5. Tang, K. L., M. K. Agnew, W. J. Chen., M. V. Hirt, T. Sado, L. M. Schneider, J. Freyhof, Z. Sulaiman, E. Swartz, C. Vidthayanon, M. Miya, K. Saitoh, A. M. Simons, R. M. Wood, and R. L. Mayden, 2010 - Molecular Phylogenetics and Evolution 57(1): 189-214
   Systematics of the subfamily Danioninae (Teleostei: Cypriniformes: Cyprinidae).
6. Tejavej, A., 2012 - Zootaxa 3586: 148-159
   Redescription of Barilius ornatus Sauvage (Cypriniformes: Cyprinidae) with data from a population from the eastern part of the Isthmus of Kra, Thailand.