Taxonomy & naming
Neolebias kerguennae was described by the French ichthyologist Jacques Daget in 1980. It sits in the genus Neolebias, a group of small West and Central African characins within the family Distichodontidae — the same family that contains the far larger, plant-grazing Distichodus species and the deep-bodied citharinids, underscoring how much body-plan and size diversity this African characin lineage spans. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the governing authority for the valid name and combination used here; nothing in the available sources suggests a pending revision of the species or its placement in Neolebias.
The species epithet honours Mrs Kerguenne Daget, widow of the ichthyologist Jacques Daget himself — an eponym rather than a descriptive term. No subspecies or named colour variants are documented, and the species has no established common name in general use, reflecting how little exposure it has had outside specialist ichthyological literature.
Morphology
Neolebias kerguennae is a genuinely tiny fish: FishBase records a maximum size of 1 in standard length (roughly 1.5 in total length), placing it among the smallest characiforms known. Meristic data available from FishBase list 12–13 dorsal soft rays and 9–11 anal soft rays, consistent with the slender, elongate body shape typical of small Neolebias species.
Detailed descriptions of colouration and fin pattern are not available in the sources consulted for this account, and no photographs or aquarium observations could be confirmed. Data are sparse enough that specific claims about colour, sexual dimorphism, or fine anatomical detail are not made here rather than inferred from congeners.
Habitat
The species is endemic to Lower Guinea, restricted to coastal river drainages in Gabon, Central Africa — a small-range endemic in the classic sense, found nowhere else. FishBase characterises its environment as tropical freshwater, with a documented temperature range of roughly 75–82 °F, consistent with the generally warm forest-stream conditions typical of coastal Lower Guinea drainages.
No further detail on specific water chemistry, substrate, or stream structure was found in the sources available. Given the genus and region, a shaded, soft, tannin-influenced forest-stream setting is plausible by analogy with other small Neolebias species, but that inference is not confirmed for this species specifically and is not asserted as fact here.
Feeding
FishBase assigns Neolebias kerguennae a trophic level of 3.3, indicating a diet built around small invertebrates and other small organisms rather than plant material or detritus — a micropredator/omnivore position typical of tiny stream characins, and a contrast to the herbivorous grazing habits of its much larger Distichodontidae relatives.
No specific dietary items (e.g. particular invertebrate groups) are documented in the available sources. In the near-total absence of aquarium accounts, feeding recommendations cannot be given with confidence beyond the general expectation, based on trophic level and body size, that this is a fish suited to fine live and frozen foods rather than flake or pellet aimed at larger fish.
Mating
No courtship or pairing behaviour has been documented for Neolebias kerguennae in the sources available for this account. The species is not established in the aquarium trade, and no hobbyist or scientific breeding reports were found.
Breeding
Breeding biology for Neolebias kerguennae is undocumented. Within the wider Distichodontidae, the family's larger genera (Distichodus and the citharinids) are egg-scattering species that are rarely bred at home even by experienced keepers, and there is no indication that Neolebias kerguennae departs from an egg-scattering strategy typical of small characins. However, no clutch size, spawning trigger, incubation period, or parental-care behaviour has been recorded for this specific species, and none is invented here. This is a case where the honest statement is that breeding in captivity has not been documented.
In the aquarium
Neolebias kerguennae is essentially absent from the aquarium hobby: no dedicated species profile, care sheet, or husbandry account could be located, even on hobbyist sites that cover other Neolebias species such as N. trilineatus and N. ansorgii. Prospective keepers should treat this as a species with no established aquarium track record rather than assume it can be kept like its better-known congeners.
What can be said with confidence is scale: at a maximum of 1 in SL, this is an extreme nano fish, and any tank housing it would need to be sized and stocked accordingly, with very fine-mouthed tankmates only, if any. Given its Endangered status and the total absence of trade or captive-breeding records, this is not a species to source from wild collection, and there is no evident captive-bred supply.
Conservation
The IUCN Red List assesses Neolebias kerguennae as Endangered (EN), an assessment dating to 2009 based on criterion B2ab(iii) — a listing driven by an extremely small and fragmented geographic range (endemic to a limited set of coastal drainages in Lower Guinea, Gabon) combined with an inferred continuing decline in the extent and/or quality of its habitat, rather than a directly measured population count.
As a narrow-range endemic restricted to Gabonese coastal river systems, the species is inherently vulnerable to any localised habitat disturbance — deforestation, land-use change, or water-quality degradation within its limited drainage — even though no species-specific threat data beyond the range-based criterion were found in the sources consulted. There is no evidence of an aquarium trade in this species, so collection pressure does not appear to be a relevant factor; the conservation concern here is squarely about habitat within a very small range.