Taxonomy & naming
Ompok jaynei was described by Henry Weed Fowler in 1905. Over its taxonomic history the species has appeared under several old combinations, including Silurus jaynei and Callichrous jaynei, before being placed in the modern genus Ompok within the family Siluridae, the true sheatfishes of Asia and Europe. It belongs to the Ompok leiacanthus species group, a cluster of small Bornean and Sundaic Siluridae.
The genus name Ompok is a vernacular Sundanese/Malay word for these slender, scaleless catfishes, adopted as a scientific genus name; the species epithet jaynei honours a collector or associate credited in Fowler's original description. As with much of Siluriformes, the family has been heavily reshuffled by molecular and morphological revision, and the Catalog of Fishes (Eschmeyer, CAS) remains the authority for the currently valid combination, Ompok jaynei.
Morphology
Like other Siluridae, Ompok jaynei has an elongated, laterally compressed, scaleless body with a long anal fin, a small or absent adipose fin, and a pair of long maxillary barbels used to feel out prey and obstacles in dark, tannin-stained water. The skin is naked rather than plated, which matters directly for aquarium medication (see "In the aquarium").
Maximum recorded size is modest for the genus: about 6 in standard length. This keeps O. jaynei well short of the pond-sized bulk some larger Ompok and related sheatfish (such as Wallago) eventually reach, though prospective keepers should still confirm adult size before buying any Ompok, since juveniles of the larger species in this genus are often sold small and grow considerably.
Habitat
Ompok jaynei is native to Borneo, recorded from Sarawak, northern Sabah and Kalimantan Timur. It inhabits freshwater and brackish peat swamp blackwaters — the acidic, tannin-stained, oxygen-poor waters typical of Southeast Asian peat swamp forest, where dissolved organic matter from decaying leaf litter colours the water dark tea-brown and depresses pH well below neutral.
This is a genuinely soft, acidic blackwater habitat, in contrast to many other catfish groups where that assumption does not hold; the species' distribution is tied closely to the peat swamp forest ecosystems of Borneo, which are under heavy pressure from drainage, logging and conversion to plantation agriculture.
Feeding
Detailed dietary studies specific to Ompok jaynei are not available in the sources consulted; data is sparse for this species. Based on the genus and family, Ompok species are nocturnal predators that take small fish, aquatic invertebrates and other prey they can swallow whole, foraging by scent and touch with their barbels in low-visibility blackwater.
In the aquarium, Ompok species typically accept sinking pellets, frozen bloodworm, prawn and other meaty foods offered after dark. Tankmates should be sized so they cannot be swallowed, and very small fish are at risk from a hunting Ompok.
Mating
No mating behaviour specific to Ompok jaynei has been documented in the sources available. Among the glass and sheatfish catfishes as a group, true glass catfish (Kryptopterus) are essentially not bred in captivity and the aquarium trade in them is wild-caught, while the larger Ompok and Wallago species are river spawners whose reproduction in the wild is tied to seasonal flooding and open water rather than any nest or brooding behaviour.
Breeding
Home aquarium breeding of Ompok jaynei is not established, and none of the sources consulted document it. Related, commercially important Ompok species such as O. bimaculatus and O. pabda are propagated at aquaculture scale using hormone induction rather than naturally in captivity, and there is no indication O. jaynei is bred this way or otherwise. Prospective keepers should treat this as a species that is collected from the wild rather than reliably captive-bred, and should not expect to breed it at home.
In the aquarium
Ompok jaynei stays smaller than its size-trap relatives at around 6 in SL, but it still needs a reasonably large, well-established tank with soft, acidic, tannin-stained water reflecting its peat swamp origin — leaf litter, driftwood and a peat-influenced filter substrate all help recreate the blackwater conditions it evolved in. Good water circulation is recommended for the genus, echoing PlanetCatfish's note that Ompok species do best with roughly ten times tank-volume turnover per hour.
As a scaleless catfish it is medication-sensitive: dose copper-based treatments and many standard medications conservatively, often at half strength, as is standard practice for naked-skinned catfish. It is nocturnal and appreciates shaded cover and caves for daytime retreat, and tankmates should be too large to be swallowed whole, since this is a predatory sheatfish that will eat small fish given the chance. Handle with care around the head region typical of Siluridae, and always move rather than net catfish with stiff fin spines to avoid tangling.
Conservation
Ompok jaynei has not been formally assessed by the IUCN Red List and its status is Not Evaluated. Related Ompok species with wider ranges, such as O. pabo and O. pabda, are assessed as Near Threatened, which gives some indication that pressures on this genus are real even where individual species remain unassessed.
As a peat swamp forest specialist restricted to Borneo, O. jaynei is exposed to the same threats affecting that habitat broadly: drainage, logging, fire and conversion of peat swamp forest to oil palm and other plantation agriculture across Sarawak, Sabah and Kalimantan. Without a formal assessment its conservation needs are not quantified, but its narrow, threatened habitat type is cause for caution.