Taxonomy & naming
Enteromius inaequalis was described in 1988 by Christian Lévêque, Guy G. Teugels and Dirk F.E. Thys van den Audenaerde — a trio of Belgian and French ichthyologists responsible for a substantial portion of the foundational work on West African freshwater fishes, including the landmark Faune des poissons d'eaux douces et saumâtres de l'Afrique de l'Ouest series. The species was originally placed in the genus Barbus, which served as a vast holding genus for African and Eurasian barbs throughout most of the twentieth century.
Subsequent molecular and morphological revisions of African cyprinids progressively split the old Barbus aggregate. The Catalog of Fishes (Eschmeyer, CAS), the standard authority for valid names, places this species in Enteromius — a genus resurrected and expanded to receive a large part of the sub-Saharan African barb radiation. The parenthetical authority in the current combination, (Lévêque, Teugels & Thys van den Audenaerde, 1988), records that the original description used a different genus name. Literature published before the Enteromius transfers may list this fish as Barbus inaequalis.
The specific epithet inaequalis is Latin for "unequal" or "uneven", likely referring to an asymmetry or unevenness in a diagnostic morphological character noted in the original description — a naming convention common in the Barbus/Enteromius group when distinguishing otherwise similar species by subtle meristic or proportional differences.
Morphology
Enteromius inaequalis is a small, moderately slender barb in the typical Enteromius body plan: fusiform and laterally compressed, with a relatively small head, a subterminal to terminal mouth, and the two pairs of barbels (rostral and maxillary) characteristic of many members of the genus, though barbel number and development vary across the group. The body is silvery to pale gold on the flanks, lighter ventrally, with pigmentation details — including any lateral stripe, spots, or scale-edge markings — that distinguish it from sympatric congeners.
Formal meristic and morphometric data are confined to the primary description; secondary sources covering the full suite of scale counts, fin-ray formulae and body proportions in English are sparse. Maximum size has not been reliably reported in accessible sources; as a member of the small-bodied West African Enteromius assemblage, the species is expected to be in the 2–4 in standard length range typical for the group, but a precise figure is not confirmed here.
Sexual dimorphism, where described at all in related species, typically involves females becoming noticeably deeper-bodied and rounder when gravid, while males may develop small breeding tubercles on the snout during the spawning season.
Habitat
Like the majority of small West African Enteromius, this species inhabits flowing fresh waters — principally rivers, streams and their tributaries across the relevant drainage basin or basins covered by the original description. West African river habitats in this ichthyofaunal zone range from clear, moderately fast headwater streams over gravel and rock substrates to slower lowland reaches over sand and mud, often with seasonally fluctuating water levels driven by the pronounced wet and dry seasons of the Sudanian and Guinean climate zones.
Water chemistry in these systems is typically soft to moderately hard, with pH values that can range from mildly acidic forest-margin streams to near-neutral or slightly alkaline savanna-influenced waters. Specific temperature, pH and hardness data for this species are not reported in accessible sources; ambient river temperatures across West Africa at low to mid altitudes are broadly in the range of 72–82 °F, varying with season and elevation. Enteromius inaequalis is presumed to be an opportunistic, benthopelagic shoaler that uses both the water column and the bottom zone of its stream habitats.
Feeding
Small West African Enteromius are generalist omnivores, and Enteromius inaequalis is expected to follow the same dietary strategy: taking small aquatic and terrestrial invertebrates (insect larvae, crustaceans, worms), algae, plant fragments and organic detritus from the substrate and water column. This broad dietary flexibility is adaptive in seasonal stream environments where food availability fluctuates significantly between the wet season, when allochthonous input from flooded bank vegetation is high, and the dry season, when streams contract and food sources become more concentrated.
No species-specific gut-content studies for E. inaequalis are available in the accessible literature. Observations of related West African Enteromius in comparable habitats consistently show the same opportunistic omnivorism, with the relative proportions of invertebrate prey versus plant and algal material shifting with habitat type and season.
Mating
Enteromius inaequalis reproduces by egg-scattering, the reproductive strategy universal among barbs. There is no nest, no pair bond, and no parental care. When sexually ripe, males pursue gravid females through aquatic vegetation or over gravel and sandy substrates in a characteristic driving behaviour, pressing close alongside the female as eggs and milt are released simultaneously. The adhesive or semi-adhesive eggs sink among plant stems, fine gravel or leaf litter, where they develop unattended.
Spawning in West African stream fishes is typically seasonal, peaking at or near the onset of the wet season when rising water temperatures, increasing flow, and improved food availability bring fish into breeding condition. The seasonal flood pulse in these environments synchronises reproduction across many species within the same drainage, and Enteromius are no exception. Males may colour up more intensely during the breeding season, though specific accounts for this species are not documented.
Breeding
As an egg-scattering barb, Enteromius inaequalis gives no parental care whatsoever. Eggs are scattered over the substrate or among vegetation and are immediately abandoned; adults — including the parents — will consume eggs if they encounter them. Development time is temperature-dependent: at the warm temperatures of West African rivers, eggs of small barbs typically hatch within 24–48 hours, and larvae become free-swimming a few days after that.
The species has not been reported as bred in the aquarium hobby in the accessible literature, and no specific captive-breeding protocols exist. General barb breeding methodology — conditioning fish on live and varied foods, providing fine-leaved plants or a spawning mop, and removing adults after spawning — would be the logical starting framework for any captive attempt, following the egg-scattering template common to the entire group.
In the aquarium
Enteromius inaequalis does not appear in the mainstream aquarium trade and is essentially unknown to the hobby. No importation records, husbandry notes or captive-maintenance reports for this species are available in the accessible hobby literature. West African Enteromius in general are underrepresented in the trade compared with their Asian counterparts, and obscure species described from localised river systems — particularly those without distinctive colouration or a common name — rarely reach specialist importers.
Should the species ever become available, general West African stream barb husbandry would apply: a well-oxygenated tank with moderate current, a neutral to slightly acidic pH, soft to moderately hard water reflecting the riverine conditions of the native range, and temperatures in the low-to-mid twenties Celsius. Being a shoaling species, a group of six or more individuals would be appropriate to express natural behaviour.
Conservation
Enteromius inaequalis has not been formally assessed by the IUCN Red List; its conservation status is Not Evaluated (NE). Many small, narrowly distributed West African Enteromius share this status — they were described from limited collections and have not been resurveyed with sufficient frequency or geographical coverage to support a Red List assessment. The absence of an assessment does not indicate security; it reflects a data gap.
The freshwater ecosystems of West Africa face growing pressure from agricultural expansion, deforestation and associated sedimentation, small dam construction, water extraction for irrigation, and pollution from agro-industrial and artisanal mining activities. River basins in the Guinean and Sudanian zones have seen accelerating habitat modification over recent decades. For narrow-range specialists or species with small, fragmented populations — categories that many West African Enteromius fall into by default — these pressures can translate into range contraction or local extirpation long before formal assessments are conducted. Broader survey work targeting the West African cyprinid fauna would be required to establish a clearer picture of this species' status.