Taxonomy & naming
Ctenopoma garuanum was described by Ernst Ahl in 1927, with the type locality given as Garua (also spelled Garoua or Garua), in the hinterland of Cameroon — a town on the upper Benue River system in northern Cameroon. The original authority appears in parentheses, indicating that Ahl placed the species in a different genus before it was transferred to Ctenopoma; Eschmeyer's Catalog of Fishes is the governing reference for the valid name and authority.
The genus Ctenopoma (family Anabantidae) encompasses the African bushfishes, a diverse group of labyrinth fishes distributed across sub-Saharan Africa from West Africa to the Congo Basin and East Africa. The family Anabantidae unites the African bushfishes with the Asian climbing perch (Anabas) and a handful of related genera; all share the defining suprabranchial labyrinth organ that allows them to breathe atmospheric air. Within Ctenopoma, species range widely in size, from small forest-stream inhabitants such as C. garuanum to the much larger C. acutirostre and C. kingsleyae. The specific epithet garuanum references the type locality, Garua.
The species has not been subject to a detailed phylogenetic revision in recent decades, and its placement within intrageneric groupings of Ctenopoma should be treated as provisional pending molecular work on the genus.
Morphology
Ctenopoma garuanum is a small, laterally compressed anabantoid with a maximum recorded total length of 2 in. Like other members of the genus it has the characteristic body plan of a compact, deep-bodied bushfish: a slightly humped dorsal profile, a moderately large mouth suited to engulfing invertebrate prey, and ctenoid scales that give the genus its name (Greek: ktenos, comb + poma, cover — referring to the serrated preopercular spine present in many species).
Detailed colour descriptions for living C. garuanum are sparse in the published literature, reflecting how infrequently the species is observed in the field or kept in captivity. Based on related small Ctenopoma species and the limited museum-specimen data, the body is likely brownish to olive with lateral markings; many small Ctenopoma display faint vertical barring or mottling that provides camouflage among vegetation and roots. Sexual dichromatism, if present, has not been formally documented for this species.
The labyrinth organ — a folded, vascularised chamber above the gill arches — is well developed, as in all Ctenopoma, and the fish must access the water surface to breathe air. This morphological adaptation underlies the species' tolerance of warm, poorly oxygenated water bodies typical of West and Central African lowland habitats.
Habitat
The type locality of Ctenopoma garuanum is the Garua area of northern Cameroon, within the upper Benue River drainage. The Benue is a major tributary of the Niger, and this positions C. garuanum within the Niger-Benue river system rather than the Congo Basin — making it somewhat unusual among smaller Ctenopoma species, many of which are Congo or Guinea-coast endemics. Distribution data remain limited, and the species may be endemic to the Cameroon portion of this drainage.
Based on genus-level ecology, C. garuanum is expected to inhabit slow-moving rivers, floodplains, forested streams, and swampy margins with dense vegetation, submerged roots, and overhanging cover. Ctenopoma are predominantly fish of still or sluggish water where their air-breathing habit is advantageous: oxygen levels in such habitats fluctuate widely, and the ability to supplement gill respiration with atmospheric air is essential. Temperatures in the upper Benue lowlands are tropical, consistent with the FishBase classification of the species as a tropical freshwater fish.
No detailed field studies specifically documenting the microhabitat preferences, water chemistry, or seasonal ecology of C. garuanum at its type locality appear to have been published, and much of the ecological profile must be inferred from the broader genus biology and regional drainage context.
Feeding
Ctenopoma species are carnivorous predators, and C. garuanum is expected to share this dietary strategy. The genus as a whole feeds primarily on small fish, insects, crustaceans, and aquatic invertebrates, hunting by stealth among vegetation and root tangles rather than by pursuit in open water. The slightly upturned mouth and laterally compressed body are consistent with a lie-and-lunge or slow-stalk approach to prey capture, similar to what has been described for other small Ctenopoma.
Given its small maximum size of 2 in, C. garuanum is restricted to correspondingly small prey items: aquatic insect larvae, small crustaceans, worms, and other invertebrates would constitute the bulk of the natural diet. Larger conspecifics and other small fish fry are also likely taken opportunistically where available.
In captivity, small Ctenopoma generally accept a diet of live and frozen invertebrates — bloodworm, brine shrimp, Daphnia, small chironomid larvae — and may eventually learn to take high-quality prepared foods. Like most small anabantoids, they benefit from variety and may be reluctant to switch to dried foods without patient conditioning.
Mating
Reproductive behaviour has not been directly studied or documented in published accounts for Ctenopoma garuanum. However, broader Ctenopoma biology provides useful context: members of the genus that have been observed in captivity or the field are open-water egg scatterers, releasing buoyant or semi-buoyant eggs with no nest construction and no parental care. This mode — shared with a number of African anabantoids including the climbing perch (Anabas) and the kissing gourami (Helostoma) — contrasts with the bubble-nesting and mouthbrooding strategies seen in many Asian labyrinth fishes.
In egg-scattering Ctenopoma, males and females approach one another in open water or near the surface, and eggs are released and fertilised in a brief spawning embrace or parallel swim. The eggs, being buoyant, rise to the surface or drift among floating vegetation, where they are left entirely unattended. No territory is established, no nest prepared, and neither parent guards the spawn or fry.
Given the small body size of C. garuanum, courtship behaviour is unlikely to involve the elaborate flaring and chasing seen in larger species, but specific observations have not been recorded.
Breeding
As with mating, no dedicated captive-breeding account for Ctenopoma garuanum appears in the aquarium literature, reflecting how rarely this species has been kept and bred. Extrapolating from the broader Ctenopoma egg-scatterer mode: spawning likely occurs near or at the water surface, with buoyant eggs released into open water or drifting among surface vegetation. No parental care follows — eggs and subsequent fry are abandoned immediately after spawning, and adults may eat the spawn if not separated.
Incubation time and fry development have not been recorded for C. garuanum, but in analogous small African anabantoids, eggs hatch within one to two days at tropical temperatures, and the larvae initially depend on yolk-sac reserves before becoming free-swimming. First foods at the free-swimming stage would be very small live prey such as infusoria or freshly hatched brine shrimp nauplii.
For any aquarist who obtains this species, treating it as an open-water egg scatterer and removing eggs or the adults promptly after spawning is the recommended approach until species-specific data become available.
In the aquarium
Ctenopoma garuanum is extremely rare in the aquarium hobby and is not commercially bred or regularly traded. Any specimens available would almost certainly be wild-caught, and obtaining them would require specialist contacts with West African fish importers. The species' small size of 2 in makes it potentially more tractable in a modestly sized aquarium than larger Ctenopoma such as C. acutirostre or C. kingsleyae, which can exceed 6 in.
General husbandry principles for the genus apply: a well-planted aquarium with slow or gentle filtration, warm tropical temperatures (around 75–79 °F based on the upper Benue latitude), subdued lighting, and plenty of hiding places among roots, driftwood, and dense vegetation. Like all labyrinth fishes, C. garuanum must be able to reach the water surface to breathe air — a tight-fitting lid is essential to prevent jumping, and the gap between the water surface and the cover glass should be kept warm to avoid chilling the labyrinth organ during air breathing.
As a carnivore, it should be housed with tankmates too large to eat and not so boisterous as to outcompete it for food. Other small, gentle West African fishes would be natural candidates. Its predatory nature means very small fish or fry would be at risk as tankmates.
Conservation
Ctenopoma garuanum has not been evaluated by the IUCN Red List and carries a status of Not Evaluated (NE). No published conservation assessment, population survey, or threat analysis specific to the species is known. Its apparent restriction to the upper Benue River drainage in Cameroon gives it a relatively narrow range by the standards of large river systems, though the Benue is a substantial watercourse with extensive tributaries.
The upper Benue drainage in northern Cameroon faces general pressures common to West-Central African freshwaters, including agricultural land-use change, sedimentation, fishing pressure, and in some areas water extraction. Whether C. garuanum is affected by these pressures, or how abundant it is within its range, cannot be determined from available data.
Given its obscurity and the lack of trade interest, it is unlikely to have experienced the collection pressure that has affected more popular Ctenopoma species. Formal assessment by the IUCN would require contemporary field surveys to establish distributional limits and population status.