Taxonomy & naming
Haplochromis simba was described in 2022 by Nathan Vranken, Maarten Van Steenberge, Annelies Heylen, Eva Decru and Jos Snoeks in the European Journal of Taxonomy, in a monograph tellingly titled 'From a pair to a dozen: the piscivorous species of Haplochromis (Cichlidae) from the Lake Edward system.' Before that paper only two fish-eating haplochromines were recognised from Lake Edward; the authors raised the count to roughly a dozen, describing ten new species at once — Haplochromis simba among them, alongside Haplochromis latifrons, Haplochromis rex, Haplochromis glaucus, Haplochromis aquila, Haplochromis kimondo, Haplochromis falcatus, Haplochromis curvidens, Haplochromis pardus and Haplochromis quasimodo. The holotype is an adult male of 4 in standard length (RMCA 2016.035.P.0225), held at the Royal Museum for Central Africa in Tervuren, Belgium; it was bought at the Rwenshama landing site on the Ugandan shore of Lake Edward (0°24′16″ S, 29°46′25″ E) in November 2016. Paratypes include older material from the Congolese side near Vitshumbi, collected by a Belgian expedition in 1953. The genus Haplochromis is famously a taxonomic holding pen: the East-African 'haplochromines' are a vast, rapidly evolved species flock, and most authors expect the catch-all genus to be split as the radiation is resolved. The describers nonetheless placed the species in Haplochromis, within the tribe Haplochromini of the subfamily Pseudocrenilabrinae, and that is the heading retained here. Within the Lake Edward assemblage simba belongs to the 'macrodontic' guild of piscivores — those with few, large oral teeth — as opposed to the small-toothed 'microdontic' predators.
Morphology
Haplochromis simba is a small, shallow-bodied predator; the type series spans 3.5–4.5 in SL and the holotype is 4 in, with FishBase giving a maximum of about 4.5 in SL — a hand-sized fish. The body is oval to slightly pear-shaped with a shallow caudal peduncle, and the head is long and narrow with a small, high-set eye and a gently sloping snout. The diagnostic features lie in the jaws: the premaxillary pedicel and the mental (chin) prominence are strongly developed, and the outer oral teeth are few but very large and unicuspid (22–31 in the upper jaw, widely and irregularly spaced) — the macrodontic dentition of a fish that seizes comparatively large prey. Colour is where the species earns its name. Dominant (breeding) males turn bright yellow over the body with an orange operculum, cheek and anterior flank, white belly and chest, pink lips and lower jaw, and a faint crimson wash on the anal and lower caudal fins; the anal fin carries two or three very large orange egg-spots ringed in clear. Females and juveniles are a quieter yellow over the body and cheek with a white belly and yellow fins, lacking the orange forebody and bold egg-spots. This is the typical haplochromine pattern of a drab female and a flag-coloured territorial male, and it is the principal basis on which the sexes — and the species — are told apart.
Habitat
Haplochromis simba is known only from Lake Edward, a relatively small (~2,186 mi²), shallow lake of the western (Albertine) arm of the East African Rift that lies between Uganda and the Democratic Republic of the Congo and drains, via Lake George and the Kazinga Channel and ultimately the Semliki River, into the Nile system. Within the lake the species is recorded from inshore areas over hard, rocky substrates, where its specimens were collected at landing sites such as Rwenshama (Uganda) and along the Congolese shore near Vitshumbi. Lake Edward is a warm, weakly stratified tropical lake: surface waters typically run above 77 °F with only about a 34 °F gradient down to the bottom, and like its rift neighbours the lake is mineral-rich and alkaline, with a high pH (on the order of 8.5–9). These are not the soft, acidic blackwaters of the Amazon but hard, buffered rift water, the same broad chemistry that East-African cichlid keepers replicate for Victoria, Edward and Malawi fishes. The species' shallow, hard-substrate niche sets it apart from several congeners in the same study that were trawled from open water tens of metres deep.
Feeding
On the evidence of its anatomy, Haplochromis simba is a piscivore — a fish-eater. The whole monograph that named it is built on identifying a piscivorous morphology: a long, narrow, isognathous-to-prognathous jaw, a wide gape, an enlarged and prominent premaxillary pedicel, and a strong mental prominence, all hallmarks of a cichlid that lunges at and grips other fish. simba sits in the 'macrodontic' camp, with few but large, widely spaced teeth suited to holding sizeable prey, in contrast to the many-small-toothed 'microdontic' predators of the same lake; this dental split is interpreted as ecological partitioning of hunting technique, prey type and prey size among the lake's predators. FishBase places the species at a trophic level of about 3.4, consistent with a secondary consumer that takes small fishes. No stomach-content study has yet been published, so the diet is inferred rather than directly observed — but in a lake whose haplochromine flock is itself the dominant prey base, a small predator like simba almost certainly preys on smaller cichlids and other inshore fishes.
Mating
No field study of courtship has been published for Haplochromis simba specifically, but its biology can be read from its anatomy and from the well-documented behaviour of the East-African haplochromine flock to which it belongs. These cichlids are polygynous and lek-like: males develop bright nuptial colour — here the lion-yellow body and orange forebody of dominant males — and the conspicuous orange egg-spots on the anal fin are a classic haplochromine courtship device, used to lure the female during spawning. Dominant males hold and defend territories and display to passing females, while non-dominant males remain drab and subordinate (the description notes a muted, pink-tinged non-dominant male morph). There is no lasting pair bond; the male's role ends at fertilisation. The marked difference between the gaudy territorial male and the plain female is itself the signature of this mating system.
Breeding
Breeding has not been documented directly in Haplochromis simba, but every line of evidence points to the standard East-African pattern: it is a maternal mouthbrooder. The large orange egg-spots on the male's anal fin are the diagnostic tell — in haplochromine spawning the female lays a small clutch on the substrate, immediately takes the eggs into her mouth, and is enticed to nip at the male's dummy egg-spots, drawing in milt to fertilise the brood inside the buccal cavity. The female then carries the developing eggs and larvae in her mouth for roughly two to three weeks (the genus-typical incubation), releasing free-swimming fry that may continue to shelter in her mouth when threatened; the male provides no parental care. Clutch sizes are not recorded for this species; congeneric Lake Edward and Lake Victoria haplochromines of similar size typically carry only a few dozen eggs (commonly on the order of 20–60), a small fecundity that is the trade-off for the protection mouthbrooding affords. These figures are stated here as genus-typical estimates, not measurements from simba itself.
In the aquarium
Haplochromis simba is, for all practical purposes, not an aquarium fish. It was described in 2022 from museum and freshly collected scientific material, has no presence in the ornamental trade, and is not bred by hobbyists; there is no body of keeping experience to report, and anyone who claims to keep 'Haplochromis simba' almost certainly has a different, more familiar Victorian or Edward haplochromine. The honest husbandry note is therefore about the type of fish it is rather than this species in particular. Were it ever maintained, it would need the conditions of any hard-water rift haplochromine: alkaline water (pH roughly 7.5–9) of moderate-to-high mineral content and a temperature around 75–82 °F, with a rocky inshore-style aquascape. As a small piscivore it would regard any tankmate it could swallow as food, and as a polygynous haplochromine it would do best in a male-with-several-females group in a spacious tank, since a single dominant male will harass rivals and over-pursue lone females. None of this is a recommendation to seek the fish out — it is a wild, range-restricted endemic of conservation interest, not a candidate for the hobby.
Conservation
Haplochromis simba has not yet been assessed by the IUCN Red List (status Not Evaluated as of this writing), which is unsurprising for a fish described only in 2022. That absence of a formal status should not be read as security. Lake Edward's cichlid flock is far less studied than those of Victoria, Malawi or Tanganyika, and the whole assemblage faces real pressures: an intensifying artisanal and commercial fishery (simba's own type specimens were bought at fish-landing sites), catchment deforestation and sedimentation, agricultural and urban runoff, and the looming prospect of oil exploration in the Albertine Rift. The cautionary parallel is Lake Victoria next door, where the introduction of Nile perch and other changes drove the most catastrophic vertebrate extinction event of modern times among its haplochromines. Lake Edward has so far escaped that fate and retains a substantially intact native fauna, but a small, hard-substrate endemic known from only a handful of specimens is intrinsically vulnerable, and a proper assessment of its range and population is a genuine gap. As a narrow-range Albertine Rift endemic, its long-term prospects are tied entirely to the health of this one lake.