Taxonomy & naming
Enteromius bourdariei was described by Jacques Pellegrin in 1928. Pellegrin placed it in what was then a broad conception of the African barb fauna, and the species has been carried under the large, polyphyletic genus Barbus for much of its taxonomic history — a common fate for small African cyprinids whose systematic placement remained unresolved for decades.
The wholesale reorganisation of African small barbs in the early twenty-first century, following molecular and morphological work that demonstrated Barbus sensu lato to be deeply polyphyletic, transferred the great majority of sub-Saharan small barbs to Enteromius, the genus erected to contain them. The Catalog of Fishes (Eschmeyer, CAS) records the current valid combination as Enteromius bourdariei (Pellegrin, 1928), with the parenthetical authority denoting the move from the original genus. No infraspecific variants are currently recognised.
Morphology
Enteromius bourdariei is a small barb reaching a reported standard length of approximately 4.5 in, which is relatively large for the genus and places it among the bigger members of the African small-barb assemblage. The body form is the typical compressed, moderately deep cyprinid shape shared across the genus, with small barbels, a terminal mouth, and a simple, unremarkable fin arrangement.
Detailed published descriptions of colouration and external morphology for this species are sparse in the accessible literature. As with many Enteromius known from limited material, a thorough redescription drawing on fresh specimens has not been widely circulated in the English-language ichthyological press.
Habitat
The species is endemic to the Noun River and Lake Monoun in the western highlands of Cameroon. The Noun River is a major tributary of the Wouri system, draining the Bamileke plateau, a landscape of volcanic highlands, grassland, and montane forest in the West Region of Cameroon. Lake Monoun is a small crater lake of volcanic origin in the same region, historically notorious for the 1984 limnic eruption in which dissolved CO₂ suddenly escaped from the lake's deep anoxic waters.
The specific microhabitat preferences of E. bourdariei within the Noun system — water velocity, substrate type, vegetation associations — are poorly documented in the accessible literature. The broader Noun drainage carries warm, moderately turbid water typical of savanna-influenced highland rivers in West Africa, with chemistry varying seasonally. Data on the precise temperature, pH, and hardness tolerances of this species are sparse.
Feeding
No targeted dietary study of Enteromius bourdariei has been published in the accessible literature. Based on the feeding ecology of comparable small Enteromius species from West and Central African river systems, the species is presumed to be an opportunistic omnivore — taking small aquatic invertebrates, algal and biofilm material, organic detritus, and plant fragments as available.
The Noun River system supports a seasonally variable food base tied to the highland rainfall regime, with invertebrate abundance highest during and after the wet season. Small barbs in comparable savanna-highland drainages typically forage along the bottom and in the water column, shifting diet with seasonal resource availability.
Mating
Like all barbs, Enteromius bourdariei is an egg-scattering, non-guarding spawner. No dedicated behavioural study of this species exists, but the reproductive strategy is consistent across the barb clade: a gravid female is pursued by one or more males through vegetation or over the substrate, and eggs and milt are released together without the formation of a lasting pair bond or any territorial claim beyond the transient courtship itself.
In highland African rivers, spawning is typically cued by the onset of the wet season, when rising water levels, increased turbidity, and cooler temperatures signal optimal conditions. Eggs and milt are broadcast into the water column or scattered among aquatic plants and submerged debris, after which the adults take no further interest in the spawn.
Breeding
Enteromius bourdariei has not been documented in captive breeding in the accessible hobbyist or scientific literature, likely reflecting its restricted range, rarity in the ornamental trade, and limited availability outside its native Cameroon. There is no record of the species being bred commercially or kept in public aquaria.
As an egg-scattering barb, it can be expected to follow the standard pattern for the genus: adhesive eggs scattered over fine-leaved plants, roots, or gravel substrate with no parental care and active predation of the spawn by the adults themselves. Exact clutch size, incubation duration, and larval development are undocumented.
In the aquarium
Enteromius bourdariei is not an aquarium fish in any practical sense. It does not appear in the ornamental trade and is unknown in the hobby outside of Cameroon. Its IUCN Endangered status and highly restricted natural range make collection for the trade inadvisable, and there is no captive population outside its native waters that could sustain interest in the species.
For the rare specialist institution with access to specimens — a zoological facility or research aquarium working with Cameroonian endemics — the general requirements for a highland West African Enteromius would apply: moderately warm water reflecting the highland river environment, good oxygenation, and a varied omnivore diet. Practically, the species is a conservation subject rather than an aquarium one.
Conservation
Enteromius bourdariei is assessed as Endangered (EN) on the IUCN Red List (2022 assessment), reflecting the extreme restriction of its range to the Noun River system and Lake Monoun in western Cameroon. A species confined to a single river basin and a small crater lake is inherently vulnerable to any disturbance affecting those water bodies — catchment degradation, agricultural runoff, water extraction for irrigation, and infrastructure development in the densely populated Bamileke plateau all pose realistic threats.
Lake Monoun itself has an unusual additional vulnerability: it is a meromictic crater lake with deep anoxic, CO₂-saturated water, subject to the same limnic-eruption risk that killed approximately 37 people in 1984. Degassing installations have been added to manage that risk, but the lake's unusual chemistry limits the habitat it can provide to fish confined to its oxygenated surface waters. The Noun River basin faces intensifying agricultural pressure, and the combined catchment of E. bourdariei is small enough that population fragmentation or local extirpation events could be irreversible.