Taxonomy & naming
Clarias dumerilii was described by the Austrian ichthyologist Franz Steindachner in 1866. It belongs to the family Clariidae, the airbreathing or walking catfishes, and to the genus Clarias, a large Old World group of more than 60 species spread across Africa and Asia. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the modern authority for the valid name Clarias dumerilii within Clariidae.
The genus name Clarias derives from the Greek chlaros, roughly "lively" or "vigorous", a fitting label for fish that can survive out of water for extended periods and even move overland between pools. The species epithet dumerilii honours the French herpetologist and ichthyologist Auguste Duméril, a common nineteenth-century convention for naming new species after a respected colleague. As with many Clariidae, older literature sometimes lumps regional Congo basin populations under broader species concepts; C. dumerilii is recognised as its own valid species restricted to a specific part of the Congo system.
Morphology
Clarias dumerilii shows the unmistakable clariid body plan: an elongated, cylindrical trunk that tapers gently toward a rounded tail, a flattened, bony head, and a long-based dorsal fin that runs for most of the body length, mirrored by a similarly long anal fin. FishBase records 65–81 dorsal soft rays and 51–62 anal soft rays, with no dorsal spine — the fin is entirely soft-rayed, though the pectoral fins each carry a single stiff, serrated spine that can be locked erect.
The skin is completely scaleless and covered in mucus, which matters directly for care (see "In the aquarium"). Four pairs of barbels fringe the mouth, used to feel out food in murky or dark water. Reported maximum size is 12 in total length (FishBase) — a genuinely large catfish, not a nano species, and one that keeps growing for years given adequate food and space. Like all Clarias it carries a suprabranchial (labyrinth-like) accessory breathing organ above the gills, allowing it to gulp air at the surface and tolerate low-oxygen water that would kill most fish.
Habitat
Clarias dumerilii is native to Central Africa, restricted to the middle and upper Congo River basin — specifically the eastern Kasaï and Aruwimi drainages and the upper Congo mainstem — with additional populations recorded from the Cuvo (Cueve) and Kunene rivers in Angola. It is a tropical freshwater, demersal fish, living on or near the bottom of rivers, floodplain pools and associated backwaters.
Detailed water chemistry data specific to C. dumerilii is sparse, but related Congo basin Clarias tolerate a wide range of conditions, from well-oxygenated river channels to warm, oxygen-poor floodplain pools where the suprabranchial organ becomes essential. As an air-breathing walking catfish it is adapted to survive seasonal drying and stagnant water that would be uninhabitable for gill-only fish, and it can migrate overland between pools during wet-season flooding.
Feeding
Clarias dumerilii is a nocturnal predator and opportunistic omnivore in the mould of its genus, using its barbels to locate prey in low light or murky water. Wild diet is expected to include fish, aquatic invertebrates, crustaceans and any other animal matter it can overpower and swallow, supplemented opportunistically with plant material.
Where kept, it takes large meaty foods readily — whole or chopped fish, prawn, and sinking pellets or carnivore pastes sized for a big catfish. Tankmates must be too large for it to swallow whole; a hungry Clarias treats anything that fits in its mouth as food, including fish that seemed like reasonable companions when the catfish was a juvenile.
Mating
Specific reproductive behaviour for Clarias dumerilii has not been documented in the sources available. Across the genus Clarias, wild spawning is generally tied to seasonal flooding, with pairs or small groups moving into flooded marginal vegetation or shallow pools to spawn. There is no evidence of pair bonding, nest building or brood care in this genus beyond the act of spawning itself.
Breeding
Clarias dumerilii is not bred in the home aquarium. Commercially important Clarias species (most famously C. gariepinus and C. batrachus) are propagated at aquaculture scale using hormone-induced spawning — injected with pituitary extract or synthetic hormones to trigger ovulation, then stripped and artificially fertilised — because they do not reliably spawn spontaneously in captivity. There is no indication C. dumerilii is farmed at that scale, but nothing suggests it would behave differently: this is a large, food-fish-type catfish whose reproduction in captivity, where documented at all in the genus, depends on artificial hormone induction rather than aquarium conditions. Hobbyists should not expect or attempt to breed this species; there is no parental care to speak of even where induced spawning succeeds.
In the aquarium
Clarias dumerilii is not a realistic long-term aquarium fish for the vast majority of keepers. It reaches roughly 12 in total length, and a catfish of that size and bulk needs a very large, ideally pond-scale setup with robust filtration — small juveniles sometimes seen in the trade will outgrow standard home aquariums within a year or two. Anyone taking one on needs a concrete plan for its adult size before buying it.
Because its skin is completely scaleless, it is more sensitive than scaled fish to copper-based medications and many standard treatments; dose conservatively, often at half strength, and remove carbon before treating. Its pectoral spines lock rigid and can jab a keeper or snag in a net, so it should be moved in a container rather than netted. As an air-breather it must have unobstructed access to the surface and benefits from a tightly fitted, heavy lid — Clarias are notorious for escaping tanks and, once out, for surviving on land far longer than most fish. It is largely nocturnal, appreciates a dark hide or cave by day, and — like other Clarias — is a well-documented invasive species outside its native range; it should never be released into local waterways.
Conservation
The IUCN Red List assesses Clarias dumerilii as Least Concern, reflecting its presence across a reasonably broad stretch of the Congo basin (the eastern Kasaï, Aruwimi and upper Congo drainages) plus outlying Angolan river populations, without evidence of significant range-wide decline.
As with many Congo basin fish, detailed population trend data is limited, and localised pressures — habitat disturbance, water quality changes and fishing pressure in specific tributaries — are not well quantified for this species specifically. Its broad range and the general resilience of air-breathing Clarias to degraded water conditions likely buffer it against the localised threats that endanger more habitat-specialist Congo basin fish.