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Batasio fluviatilis (Day, 1888)

atasio species are small, laterally compressed bagrid catfishes generally found in fast-flowing hill streams throughout South Asia, Myanmar, the Salween and Mae Khlong drainages of Thailand and the northern Malay Peninsula. Batasio havmolleri (Smith, 1931) is currently considered a junior synonym of B. fluviatilis.


Batasio fluviatilis

They are diagnosed (together with Chandramara) from other members of the Bagridae in possessing large sensory pores on the head, a narrow mental region, the transversely elongated, bar-like entopterygoid, and the close contact of the metapterygoid with the quadrate (Mo, 1991). Batasio is distinguished from Chandramara by the absence (vs. presence) of a pair of prominent posterior processes on the anterior part of the vomer.



Batasio fluviatilis


Batasio fluviatilis



Batasio fluviatilis Occurs in rivers and streams with moderate to swift current and a predominantly rocky bottom; less often in slow-flowing streams with a muddy substrate. Hides among stones or submerged vegetation during the day and comes out at night to feed.




Adult with young - note the juvenile body pattern


Adult with young - note the juvenile body pattern




U. K. aquarist Stuart Brown has successfully spawned B. fluviatilis. Below is a short account of his thoughts and above image shows an adult and youngsters. As with most catfish the juveniles will show a different colour pattern until growing into adulthood.


"Cleaning out the filter sock on my sump and I find three stowaways. Obviously the big one ( inch and a bit) is from the first spawning. I would say the 2 smaller ones are about 2-3 weeks old. Seems large water changes are the trigger, coupled with the changing weather perhaps". (Original text from FB Group: Catfishes of the World. www.facebook.com/groups/CatfishesoftheWorld)




Dorsal spines (total): 1; Dorsal soft rays (total): 7; Anal spines: 4-5; Anal soft rays: 8 - 9. Differs from Batasio merianiensis by having length of adipose fin base 30.0-33.3% SL (vs. 22.2) and eye diameter 18.2-23.5% SL (vs. 25.9)

Distinguished from all other species of the genus Batasio, except Batasio merianiensis in having an adult colouration consisting of a dark oblique predorsal bar and a dark spot on the sides of the body below the middle of the adipose-fin base.

Aquarium Care

Not really suitable for your usual community tank as they will need special conditions such as good water flow and a cooler temperature. Good water conditions should be adhered to at all times with regular water changes to keep organic waste down to a minimum. A sand and gravel mixed substrate with scattered rocks/boulders and root works would be ideal for a good water flow. In their natural habitat plants will not be present but hardy plants such as Microsorum, Bolbitis or Anubias spp., can be grown attached to the decor (Source: SeriouslyFish)



Not especially competitive and should not be kept with much larger or more aggressive fishes. Suitably-sized, peaceful, schooling cyprinids are ideal, or if geography isn't’t an issue many characids and livebearers should also work. In addition, balitorid loaches from genera such as Gastromyzon, Pseudogastromyzon and Homaloptera are suitable, and some members of the families Cobitidae and Nemacheilidae should also be ok but proper research is essential as some can be excessively aggressive/territorial or simply grow too large. (Source: SeriouslyFish)

An egg scatterer. See above.

Sexual differences
Males possess a clearly visibly, elongate genital papilla anterior to the anal fin.

Feeds readily on any type of the usual fish foods, flakes, granulated food, frozen or live food

Glossary of Terms

Adipose fin: Fleshy finlike projection without rays, behind the rayed dorsal fin.
Dorsal fin: The primary rayed fin(s) on top of the body
Anal Fin: The median, unpaired, ventrally located fin that lies behind the anus, usually on the posterior half of the fish.
Entopterygoid: A paired bone articulating with the palatine in front.
Metapterygoid: Posterior bone that ossifies in the cartilaginous palatoquadrate arch. It first appears as a rod of bone with an anterodorsally projecting process from the middle of the dorsal surface (6.4 mm). The adult metapterygoid is roughly rectangular in shape with rounded corners and an anterodorsally projecting spine that meets the entopterygoid medially in a synostosis at its posteromedial edge. The posterior end curves dorsally to form the posteroventral surface of the orbit.
Palatine: The teeth present on the palatine bone which lies laterally in the roof of the mouth.
Vomer: The anterior bone in the mid-line of the roof of the mouth.


Batasio: From the local (Bengali) name of the fish (batasio or batashi).

Ng, H.H. and M. Kottelat 2001 A review of the genus Batasio (Teleostei: Bagridae) in Indochina, with the description of B. tigrinus sp. n. from Thailand. Rev. Suisse Zool. 108(3):495-511.
Ng, H.H. and M. Kottelat 2007 Batasio feruminatus, a new species of bagrid catfish from Myanmar (Siluriformes: Bagridae), with notes on the identity of B. affinis and B. fluviatilis. Ichthyol. Explor. Freshwaters, Vol. 18, No. 4, pp. 289-300.

Darshan, A. , N. Anganthoibi, and W. Vishwanath, 2011 - Zootaxa 2901: 52-58 Batasio convexirostrum, a new species of catfish (Teleostei: Bagridae) from Koladyne basin, India.
FB Group: Catfishes of the World. www.facebook.com/groups/CatfishesoftheWorld/

Photo Credits

Top:       © Piscesilm
Middle:   © Allan James @ ScotCat courtesy of Pier Aquatics

Bottom: © Stuart Brown





Factsheet 265

Mystus havmolleri, Mystus stigmaturus, Batasio havmolleri
Common Name:


Asia: Malay Peninsula, south of isthmus of Kra and north of Perak River basin and Terengganu River. Type locality: Klong Thalerng near Ronpibun, Peninsular Siam.
7.0cm (2¾ins)
18-23°C (63-73°F) 
6.0 -7.0.
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                                                                                                            Factsheet 265 = updated December 14, 2018 , © ScotCat 1997-2018  Go to Top