Taxonomy & naming
Pangasius lithostoma was described by the American ichthyologist Tyson R. Roberts in 1989, as part of a broader revision of the shark catfish family Pangasiidae. It sits in the subgenus Neopangasius within Pangasius, alongside a handful of other poorly known, geographically restricted species from Southeast Asian rivers. The Catalog of Fishes treats Pangasius as the valid genus for this species and the family Pangasiidae as valid; historically some pangasiid species were shuffled among other siluroid genera before the modern revisions, but Pangasius lithostoma has always stood as its own species since its description.
The genus name Pangasius derives from a local Southeast Asian vernacular name for these river catfishes. The species epithet lithostoma is built from Greek roots — lithos, "stone", and stoma, "mouth" — an allusion to a distinguishing feature of the mouth or jaw structure noted in Roberts' original description. As with many pangasiids, the species is defined by a combination of fin-ray counts, gill-raker numbers and cranial features that separate it from its close relatives, rather than by any single obvious external trait.
Morphology
Pangasius lithostoma has the classic pangasiid "shark catfish" silhouette: a streamlined, laterally compressed body, a forked tail, a tall pointed dorsal fin set well forward, and a long adipose fin behind it. The head is broad and somewhat flattened, with a terminal mouth bearing two pairs of barbels, and the eyes sit low on the head. Reported maximum size is about 10 in standard length, making it one of the smaller members of the genus rather than a giant.
Like all pangasiids the skin is entirely scaleless — smooth and naked rather than plated or scaled — which matters for medication dosing (see "In the aquarium"). The body colour is typically silvery, countershaded pale below and darker above, in keeping with a fish that swims in open water rather than hugging cover. It also carries the stiff, serrated, locking spines typical of catfishes at the leading edge of the dorsal and pectoral fins.
Habitat
This species is known only from the Kapuas River basin of western Borneo (Kalimantan, Indonesia) — the largest river system on the island — making it a narrow-range endemic as far as current records show. It is a freshwater, benthopelagic fish, meaning it swims and forages through the water column near the bottom of the river rather than sitting on the substrate, in the main channels and larger tributaries of the basin.
As an obligate air-breather, it must periodically surface to gulp atmospheric air, a trait shared with several other pangasiids and an adaptation to warm, sometimes oxygen-poor tropical river water. Detailed water-chemistry data for the Kapuas populations has not been published; the wider genus is generally associated with warm, soft-to-neutral tropical rivers rather than either strongly acidic blackwater or hard alkaline water, but this should be treated as a general guide rather than a measured record for the species.
Feeding
Specific dietary studies on Pangasius lithostoma have not been published, but the genus as a whole is omnivorous and opportunistic, with larger individuals becoming increasingly predatory. Wild Pangasius typically take aquatic invertebrates, plant matter, detritus and, as they grow, other fish and anything else they can overpower and swallow.
In captivity, Pangasius species accept a wide range of foods — pellets, sinking wafers, and meaty items such as fish, prawn and other invertebrates — and larger individuals in particular behave as opportunistic predators of tankmates. Any fish sharing water with a sizeable Pangasius lithostoma must be too large to be swallowed whole.
Mating
No published account describes courtship or spawning behaviour for this species in the wild. Commercially important Pangasiidae are generally riverine, seasonal spawners that migrate to spawn in response to the monsoon flood cycle, but nothing specific has been documented for Pangasius lithostoma, and given its Data Deficient status and lack of aquarium presence, this aspect of its biology remains essentially unknown.
Breeding
Large and commercially significant Pangasius species are propagated at industrial scale using hormone-induced spawning in hatcheries, not through natural pairing in captivity; Pangasius lithostoma, as a small-range, non-commercial species, has no record of being bred in either a farm or a home-aquarium setting. There is no parental care documented for the genus outside of the egg and larval stage in hatchery production. In practical terms, this species should be considered essentially unbred in captivity — it grows too large for casual home spawning even if that were otherwise practical, and no induced-spawning programme is known to target it specifically.
In the aquarium
Pangasius lithostoma is a poor candidate for the vast majority of home aquaria. At a documented maximum of around 10 in standard length it is smaller than the giant Pangasius species sold in the trade, but it is still a large, fast, open-water swimming catfish that needs a long tank with plenty of swimming room — this is not a fish for anything less than a very large, dedicated setup, and juveniles offered for sale (if any reach the trade) should never be assumed to stay small.
Two practical care points follow directly from its biology. First, like all pangasiids it is scaleless, so it is more sensitive than scaled fish to copper-based medications and many other treatments — dose conservatively. Second, it carries stiff, serrated, locking pectoral and dorsal spines that can snag in a net and jab the handler, so it should be moved in a container rather than netted. As an obligate air-breather it needs access to the water surface, and as an opportunistic predator any tankmates must be too large to be eaten.
Conservation
The IUCN Red List assesses Pangasius lithostoma as Data Deficient. Known only from the Kapuas River basin of western Borneo, it has not been the subject of population surveys or targeted conservation assessment, so its current status, population trend and the scale of any threats are not established in the literature.
The Kapuas basin faces general pressures common to Bornean lowland rivers — deforestation, mining, damming and agricultural runoff within the catchment — but there is no species-specific data linking these pressures to Pangasius lithostoma. Given its narrow known range, a precautionary approach to habitat protection in the Kapuas system is warranted even in the absence of a full assessment.