Taxonomy & naming
Pangasius nieuwenhuisii was described by the Dutch zoologist Christiaan Marinus Louis Popta in 1904. It belongs to the family Pangasiidae, the shark catfishes, a group of large-bodied, free-swimming Asian catfishes that has been repeatedly reshuffled between genera such as Pangasius, Pangasianodon and older combinations like Bagrus and Helicophagus as ichthyologists have revised the family; the Catalog of Fishes currently treats Pangasius nieuwenhuisii as the valid combination.
The genus name Pangasius derives from a local Javanese/Sundanese vernacular name for these river catfishes. The species epithet nieuwenhuisii honours the Dutch explorer and ethnographer Anton Willem Nieuwenhuis, who led expeditions into the interior of Borneo around the turn of the 20th century and whose collections supplied specimens to Dutch museums of the period, Popta's likely source for the type material.
Morphology
Like other Pangasius, this species has the classic shark-catfish silhouette: a streamlined, laterally compressed body, a forked tail, a tall triangular dorsal fin with a stiff leading spine, and long barbels used to feel out food on the riverbed at night. The skin is scaleless (naked), which is the norm for this family and matters directly for medicating the fish (see "In the aquarium").
FishBase records a maximum size of 23.5 in total length for this species, a genuinely large fish by home-aquarium standards even though it is modest compared to some of its giant relatives. As in most Pangasiidae, the pectoral and dorsal spines lock rigid and can jab or scrape a keeper's hand; the fish should be moved in a container rather than netted.
Habitat
Pangasius nieuwenhuisii is known only from the Mahakam River basin in eastern Borneo (Kalimantan), Indonesia — a large tropical river system draining into the Makassar Strait. It is a benthopelagic freshwater fish, living and foraging in open and mid-water zones of the main river channel rather than clinging to the bottom.
Data on its precise water chemistry preferences have not been documented in detail; as a tropical Southeast Asian river fish it can be assumed to favour warm, well-oxygenated flowing water typical of large Bornean rivers. It is a facultative air-breather, able to gulp atmospheric air to supplement gill respiration, an adaptation useful in the warm, sometimes oxygen-poor waters of tropical river systems.
Feeding
Wild diet data comes from stomach-content analysis reported on FishBase, which found very hard seeds of higher plants alongside animal matter, indicating an omnivorous diet that spans plant material and invertebrate or small prey items rather than the strict piscivory seen in some other large catfishes.
In captivity — where it should only be kept by institutions or very large systems given its size — this species would be expected to take a broad mixed diet: sinking pellets, fruit and vegetable matter, and meaty or invertebrate foods. Any tankmates would need to be far too large to be swallowed, since a 23.5 in omnivorous catfish can still take smaller fish opportunistically.
Mating
No natural courtship or spawning behaviour has been documented for Pangasius nieuwenhuisii in the wild or in captivity. What is understood about reproduction in this genus comes almost entirely from commercial aquaculture of its farmed relatives (notably Pangasianodon hypophthalmus), where natural pairing and courtship essentially do not occur under hatchery conditions — spawning is induced artificially rather than triggered by natural cues.
Breeding
As with other large Pangasiidae, this is a farm- or hormone-bred species at commercial scale and is essentially never bred in the home aquarium. Related shark catfishes are propagated by injecting synthetic gonadotropin-releasing hormones or pituitary extracts to induce spawning in ponds and hatchery tanks, producing enormous numbers of eggs (up to around 80,000 eggs per kilogram of female body weight in farmed relatives) that are then stripped and fertilised by hand.
There is no record of Pangasius nieuwenhuisii being propagated this way commercially, and given its restricted known range and Data Deficient status it should be assumed unavailable as a captive-bred fish. It grows far too large and requires infrastructure — large ponds, hormone induction, hatchery tanks — that puts reproduction entirely out of reach of home aquarists.
In the aquarium
Pangasius nieuwenhuisii is not a realistic aquarium fish and should not be purchased as a small juvenile without a clear plan for its adult size. It reaches around 23.5 in total length — the classic Pangasius size trap, where an inexpensive, active young fish quickly outgrows every home tank and typically ends up abandoned to oversized ponds, public aquaria, or worse. Prospective keepers should assume they are committing to housing a large, fast-swimming river fish for its full lifespan, not a manageable community catfish.
Because it is scaleless, it is medication-sensitive in the same way as loaches, puffers and eels — copper-based treatments and many standard medications should be dosed conservatively, often at reduced strength. Its locking pectoral and dorsal spines can snag a net and jab the handler, so it should be moved in a container. As a facultative air-breather it benefits from access to the surface. In practice, this species belongs in large public-aquarium or research settings rather than home fishkeeping.
Conservation
The IUCN Red List assessed Pangasius nieuwenhuisii as Data Deficient in 2019. It is known only from the Mahakam basin of eastern Borneo, and the assessment cites habitat degradation from deforestation, logging, and land conversion for plantation agriculture as the relevant threats within that catchment.
Because the species has such a narrow known distribution and so little published life-history data, its true population trend and vulnerability cannot currently be evaluated with confidence. Ongoing pressure on Bornean lowland rivers from logging and oil-palm expansion makes continued habitat loss a plausible long-term concern even though the formal assessment stops short of assigning a threat category.