Catfish of the Month Right November 2005

Ompok bimaculatus
Two Spot Glass Catfish, Toplettet Glasmalle (Denmark) - Ompok bimaculatus   (Bloch, 1794)

Article © Heok Hee Ng, uploaded November 01, 2005.

This article begins our 10th year of featured catfish. Who better than Heok Hee Ng to, once again, bring the montly spotlight to bear on an Asian fish with a very large distribution indeed.

The phrase "gentle predator" sounds oxymoronic, but this precisely describes the subject of this month's article, the two spot glass catfish (Ompok bimaculatus). The "gentle" part of its name comes from the fact that the fish can be housed comfortably with like-sized tankmates, and will never bother them in any way (not even an opportunistic nip). In fact, it is somewhat shy and retiring in nature, and is usually found hiding in a crevice or amongst dense vegetation. The "predator" part of the name is made self-explanatory when one looks at the upturned mouth, which is filled with sharp teeth and is somewhat reminiscent of a smaller version of the fearsome tapah (Wallago leerii). It goes without saying that small fish are not safe as tankmates; the two spot glass cat will happily snack on them, eating them in much the same manner as the tapah would (sidling up to the fish and then lunging at it and engulfing it in its large mouth).

As we currently understand, the two-spot glass cat has one of the widest distributions of all Asian catfishes (surpassed only by Bagarius yarrelli). Like B. yarrelli, the two spot glass cat consists of several species with more restricted distributions all currently lumped as one. The fish from the western (Indian) end of its distribution don't really look like those from its eastern (Southeast Asian) end. The Indian "species" (if there is only one species to be found in all of India, which is again debatable) generally have narrower heads and a silvery coloration while the Southeast Asian "species" (again, there appear to be more than one species involved) generally have wider heads and a mottled brown coloration. About the only thing the Indian and Southeast forms have in common is the presence of a distinct humeral spot (the peduncular spot, which is the other feature that gives the fish its name, is often faint and sometimes absent). Even this feature (the humeral spot) is absent in the Sri Lankan form, which are a mottled gray in color (and may represent yet another species).

The two spot glass cat is a popular food fish in India (and to a lesser extent, in Southeast Asia). The flesh is considered very tasty (which has led to its other common name of butter catfish). The Southeast Asian form (for which the name Ompok siluroides Lacépéde, 1803 appears to be the oldest available) is the one more commonly encountered in the trade. This species inhabits a wide variety of habitats (ranging from hillstreams to lakes to large rivers), and is therefore tolerant of a wide variety of water conditions. Xanthic and albino varieties (at least of the Southeast Asian form) are sometimes also encountered in the trade.

Copyright information for the images used in this article can be found on the species' full Cat-eLog page.

Down Cat-eLog Data Sheet
Scientific Name Ompok bimaculatus  (Bloch, 1794)
Common Names Two Spot Glass Catfish
Toplettet Glasmalle (Denmark)
Type Locality Tranquebar [Tharangambadi], India.
Synonym(s) Callichrous bimaculatus, Callichrous chechra, Callichrous gangeticus, Callichrous macrophthalmus, Callichrus affinis, Callichrus nebulosus, Ompok siluroides, Phalacronotus siluroides, Pseudosilurus bimaculatus, Silurus bimaculatus, Silurus chechra, Silurus duda, Silurus microcephalus, Silurus mysoricus, Wallago microcephalus
Pronunciation Awm pok
Etymology The etymology of Ompok is unclear. It is believed to be a corruption of the Indonesian name for mid-sized silurid catfishes, limpok. The specific epithet comes from the Latin bis meaning two, and macula, meaning spot; in reference to the presence of two dark spots in this species.
Down Species Information
Size 450mm or 17.7" SL. Find near, nearer or same sized spp.
Identification The catfish genus Ompok La Cepède, 1803, consists of medium-sized silurid fishes found in inland waters throughout South and Southeast Asia. The genus is traditionally diagnosed by the presence of a short dorsal fin with 4 rays, strongly forked caudal fin, subcutaneous eye that is set immediately posterior to the mouth rictus and two patches of palatal teeth (Weber & de Beaufort, 1913). Bornbusch (1995) showed that Ompok, as currently understood, is probably paraphyletic.

The two spots are found above and behind the pectoral-fin base and the other at the base of the caudal peduncle. The fish often idebntified as O. bimaculatus (and most commonly encountered in the aquarium trade) is a Southeast Asian species, Ompok siluroides which has a rounder head and a mottled brown colouration, while O. bimaculatus are silvery and have a sharper head.
Sexing Males are more slender and have strong serrations on the posterior edge of the pectoral spine (females lack these serrations).
Down Habitat Information
Distribution Asia: Afghanistan to China, Thailand and Borneo. Endangered status in the Western Ghats, India.
Thailand Waters (click on these areas to find other species found there)
Cambodia waters (click on these areas to find other species found there)
Pacific, Malaysia Waters (click on these areas to find other species found there)
Indian waters (click on these areas to find other species found there)
Bangladesh Waters (click on these areas to find other species found there)
Pacific, Greater Sunda Island Rivers, Borneo Waters (click on these areas to find other species found there)

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IUCN Red List Category Near Threatened, range map and more is available on the IUCN species page. Last assessed 2009.
pH 6.4 - 7.4
Temperature 20.0-26.0°C or 68-78.8°F (Show species within this range)
Down Husbandry Information
Feeding Readily feeds on live/frozen foods and other prepared foods such as pellets. Will also eat small fishes/shrimps. User data.
Furniture Provide plenty of hiding spaces in the form of driftwood or PVC pipes. Prefers an area of open water when active. Current preferred.
Compatibility A relatively peaceful species that is compatible with most fish of equal size or larger. Not safe with small fishes.
Breeding Not known in the aquarium. Has been bred using hormone injections in India. See also Photoperiod manipulation leads to successful voluntary captive spawning of butter catfish Ompok bimaculatus during the non-spawning breeding season.
Breeding Reports There is no breeding report.
Down Further Information
Reference Naturgeschichte der ausländischen Fische v. 8, pp 24, Pl. 364.
Registered Keepers There are 11 registered keepers, view all "my cats" data.
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There is no wish to keep this species.
Spotters Spotted this species somewhere? Click the binoculars!
There are 4 records of this fish being seen, view them all.
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Last Update 2022 Aug 16 01:22 (species record created: 2005 Nov 01 11:22)

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