Taxonomy & naming
Haplochromis snoeksi was described in 2010 by Soleil Wamuini Lunkayilakio and Emmanuel Vreven in Ichthyological Exploration of Freshwaters, from material collected in the Ngufu River — a right-bank affluent of the Inkisi River — near the village of Ngeba in the Lower Congo River basin of the Democratic Republic of the Congo, at about 1749 ft elevation. The holotype (MRAC 2007-009-P-0001) is held at the Royal Museum for Central Africa in Tervuren, Belgium, with paratypes distributed between the MRAC, the American Museum of Natural History, and the Zoologische Staatssammlung München. The authors published the name in quotation marks — '\u2018Haplochromis\u2019 snoeksi' — a deliberate signal that the genus Haplochromis is a long-standing taxonomic catch-all. As historically applied, Haplochromis is widely regarded as polyphyletic: it has accreted hundreds of African riverine and lacustrine species that do not form a natural group, and many authors now restrict the genus name pending a comprehensive revision. Eschmeyer's Catalog of Fishes lists the species as valid as Haplochromis snoeksi, and we keep the conventional generic heading here while noting that its ultimate placement is unsettled. Within the African haplochromines, snoeksi is one of a modest number of described riverine species from the Congo and Quanza ichthyofaunal provinces; the describers diagnosed it specifically against those riverine congeners rather than against any lake assemblage.
Morphology
This is a small cichlid: the type series reaches about 3.5 in standard length. The body is moderately elongate and fusiform, with a convex snout slightly longer than the eye, a terminal mouth with thick lips, and a caudal peduncle clearly longer than it is high. Fin counts are 16 dorsal spines and 9 soft rays, 3 anal spines and 6 soft rays, 15 pectoral rays and 8 pelvic rays; all scales are ctenoid. The outer jaw teeth are moderately large and bicuspid, with two to four inner rows of small tricuspid teeth, and the lower pharyngeal bone is triangular with fine, slightly stout teeth toward its posterior edge. The describers separated Haplochromis snoeksi from all other riverine haplochromines of the Congo and Quanza provinces by a unique combination of scale characters: a chest that is partially naked rather than fully scaled (as in Haplochromis bakongo, Haplochromis demeusii, Haplochromis fasciatus and several others), 16 circumpeduncular scales (versus 12 in Haplochromis oligacanthus and Haplochromis polli), and an upper lateral line of 23 scales (versus 17\u201319 in Haplochromis luluae). In life the fish is pale brown, darker above and lighter on the flanks, with no transverse bars but a sharply marked black spot on the operculum; the lower body, pectoral and caudal fins are bright yellow, and the clear, transparent anal fin carries two or three strikingly orange egg-spot ocelli ringed with a translucent margin. In preserved specimens faint vertical bars and a dark cheek bar become visible. The orange anal ocelli are the classic male haplochromine 'egg-dummy' signal used in mouthbrooder courtship; sexual dimorphism beyond these breeding markings was not detailed in the original description.
Habitat
Haplochromis snoeksi is known only from its type locality on the Ngufu/Inkisi system in the Lower Congo basin, and its true range is unknown. The describers and subsequent commentators consider it likely endemic to the upper Inkisi drainage, which is isolated in fish terms from the main Congo by a waterfall roughly 190 ft high a few kilometres upstream of the rivers' confluence \u2014 a barrier that already shelters several other endemic fishes. This is a clearwater stream fish, not a lake species: it is rheophilic (current-loving), recorded over a substrate of sand with pebbles and mud in a small river no more than about 32 ft wide and 4 ft deep, with a measured current of 0.2\u66045 ft/s. In-situ water at the type locality was warm and soft: temperature 22.1\u201325.6 \u00b0C, pH 6.5\u20137.2, and hardness 2\u20135 \u00b0dGH. The species sits in the Lower Congo Rapids freshwater ecoregion, a turbulent, biologically rich stretch of the Congo system between Malebo Pool and Matadi that is renowned for narrow-range endemism.
Feeding
No direct dietary study of Haplochromis snoeksi has been published. Its dentition \u2014 bicuspid outer teeth backed by several rows of small tricuspid inner teeth, with a fine-toothed triangular pharyngeal bone \u2014 is the generalised arrangement typical of small invertebrate-feeding and omnivorous haplochromines rather than the heavy crushing mill of a snail-eater or the elongate jaws of a piscivore. FishBase places its estimated trophic level near 3.3, consistent with a small benthopelagic carnivore taking aquatic insect larvae and other small invertebrates from a sand-and-pebble stream bed, possibly with some plant or detrital material. In the absence of gut-content data this is an inference from morphology and from the feeding ecology of comparable riverine haplochromines, and should be read as such.
Mating
Courtship and social behaviour have not been observed in this species, but its anatomy points clearly to the haplochromine pattern. The two to three orange ocelli on the male's anal fin are 'egg-spots' (egg-dummies), the signalling badge used across the haplochromine radiation: a courting male spreads the anal fin so the spots mimic eggs, drawing the female to snap at them near his vent and so take in milt to fertilise the clutch she already holds in her mouth. By analogy with its many relatives, Haplochromis snoeksi is expected to be polygynous and lek-like or territorial in the breeding season, with males displaying their yellow bodies and ocellated anal fins to passing females while the sexes otherwise lead unremarkable lives in the current. None of this has been documented in the wild for snoeksi specifically; it is the reasonable expectation for a member of this group, not a recorded observation.
Breeding
Spawning has not been described for Haplochromis snoeksi. The species belongs to the great African haplochromine assemblage, which is overwhelmingly composed of maternal (ovophile) mouthbrooders, and the well-developed orange anal egg-spots on the male are diagnostic of that reproductive style. On that basis the species is almost certainly a maternal mouthbrooder: the female takes the fertilised eggs into her buccal cavity and broods them there through hatching and the early free-swimming stage, releasing fry that may shelter back in her mouth when threatened. No clutch size has been published for snoeksi; small riverine and lacustrine haplochromines of comparable size typically carry broods on the order of a few dozen eggs (roughly 20\u201360), which is offered here only as a genus-typical guide rather than a measured figure for this fish. Spawning triggers, fry development and parental duration in the wild are all undocumented.
In the aquarium
Haplochromis snoeksi is essentially unknown in the aquarium hobby. It has no established presence in the trade, is not bred commercially, and there are no published husbandry accounts; it is a scientifically described stream fish from a remote and poorly explored corner of the Lower Congo rather than an aquarium subject. Any keeping notes can therefore only be extrapolated from its measured habitat and from experience with similar small riverine haplochromines, and should be treated as provisional. Such a fish would call for a tank arranged as a flowing clearwater stream \u2014 a sand substrate with pebbles and scattered stones, brisk, well-oxygenated current from a powerhead or stream manifold, and the warm, soft, near-neutral water recorded at the type locality (roughly 22\u201326 \u00b0C, pH about 6.5\u20137.8, low hardness). As a presumed maternal mouthbrooder it would likely be best kept as a group with several females per male to spread male attention, with broken sightlines and refuges to defuse territorial aggression at spawning time. None of this is a tested protocol: in honest terms, this is a fish for ichthyologists and field workers, not one a hobbyist is likely to encounter.
Conservation
Haplochromis snoeksi has not been evaluated by the IUCN Red List (status Not Evaluated), and it carries no CITES or CMS listing. That absence of an assessment is itself meaningful: the species is known from a single locality, is probably a narrow-range endemic of the upper Inkisi above a major waterfall, and rests on a small type series collected in 2007\u20132008. Narrowly distributed stream endemics of this kind are intrinsically vulnerable to localised pressures \u2014 deforestation and erosion in the catchment, sedimentation, water abstraction, pollution, and any alteration of the small rivers they depend on \u2014 even where no specific threat has yet been documented. The broader Lower Congo, despite its extraordinary endemic fish fauna, remains under-surveyed and under-protected, and the on-and-off insecurity of the region has long hampered the fieldwork that would clarify this species' range and status. Until that work is done, its conservation standing is best described as genuinely unknown rather than secure.