Taxonomy & naming
Haplochromis falcatus was described in 2022 by Nathan Vranken, Maarten Van Steenberge, Annelies Heylen, Eva Decru and Jos Snoeks, in a 94-page European Journal of Taxonomy monograph titled 'From a pair to a dozen: the piscivorous species of Haplochromis (Cichlidae) from the Lake Edward system'. The work is a model of the patient revisionary taxonomy that the East African haplochromine flocks demand: before it, only two piscivorous Haplochromis were formally recognised from Lakes Edward and George (Haplochromis squamipinnis and Haplochromis mentatus); the authors redescribed those two and added ten new species, falcatus among them, raising the count to a dozen. The holotype (Royal Museum for Central Africa, MRAC 2018.008.P.0401) was collected offshore of Kayanja in the Ugandan part of Lake Edward, with paratypes split between the MRAC at Tervuren and the Royal Belgian Institute of Natural Sciences in Brussels. There are no synonyms — the species was distinguished from its eleven piscivorous neighbours only by a careful combination of tooth shape, jaw proportions, body outline and adult male colour. The genus name Haplochromis is retained here as a deliberately broad container. Most of the East African haplochromines were historically lumped under it, then Greenwood's phyletic work of 1979–1980 split them into many small genera (Harpagochromis, Prognathochromis, Pyxichromis and others among the piscivores), a scheme later revisions have applied inconsistently. The describers placed falcatus in Haplochromis sensu lato rather than forcing it into one of those finer genera, and that conservative usage is followed here.
Morphology
Haplochromis falcatus is a small cichlid, reaching about 5.5 in in standard length (the largest measured specimen), with a shallow, oval body and a notably long, narrow head whose dorsal profile runs almost straight. The eye is small, the snout long and acutely pointed, and the jaws are long, slim and slope gently — the classic build of an open-water predator. The species belongs to the 'microdontic' (small-toothed) half of the Lake Edward piscivore assemblage: its outer jaw teeth are numerous (39–51 in the upper jaw), small, single-pointed and strongly recurved, set in closely packed rows, with the inner teeth equally fine and hooked. This dense palisade of little sickle-shaped teeth, rather than a few large fangs, is the feature the epithet falcatus celebrates. Counts run to 14–16 dorsal spines with 9–10 soft rays, three anal spines, and 28–30 vertebrae. Dominant males are handsome: the body is olive-green with a yellow sheen, the front of the flank and the gill cover wash a bright orange-red, the belly and chest are speckled black, and a crisp mid-lateral and dorsal-lateral stripe runs the length of each side, with several faint vertical bars on the back. The anal fin carries three small yellow eggspots ringed in clear. Females and juveniles are plainer — olive-green above, white below, keeping the two well-defined lateral stripes that help separate falcatus from several otherwise similar congeners. Sexual dimorphism is therefore clear in colour and in the male's elongated first pelvic-fin ray, the usual haplochromine pattern of a drab brooding female and a coloured display male.
Habitat
The species is endemic to the Lake Edward system, the smaller of the two western-rift lakes that, with adjoining Lake George, straddle the border between Uganda and the Democratic Republic of the Congo. All known material comes from Lake Edward proper, where the type series was taken offshore over sandy bottoms; the describers report it from sandy substrates, and its slim-bodied, small-eyed, pelagic-leaning build is consistent with a predator that hunts in open water above and around sand flats rather than in rock or weed. Lake Edward is a shallow rift lake (maximum depth roughly 361–394 ft) with warm, well-mixed, distinctly alkaline water: open-lake measurements typically give a surface pH near 9 and high conductivity (on the order of 900 µS/cm), with surface temperatures broadly in the mid-20s Celsius — a hard, basic chemistry shared across the East African haplochromine lakes. Precise depth and in-situ chemistry at the exact capture sites of falcatus were not published with the description, so the figures used here are the lake's well-documented open-water values rather than measurements specific to this fish; the honest position is that its fine-scale habitat preferences within Edward remain to be studied.
Feeding
On the evidence of its anatomy, Haplochromis falcatus is a piscivore — a fish-eater. The 2022 revision built its whole framework around piscivorous morphology, and falcatus sits squarely within it: the long narrow head, the large gape, the slim hooked jaws and especially the dense rows of small, strongly recurved teeth are the toolkit of a cichlid that seizes and holds other fish, most likely smaller haplochromines and juveniles. The describers placed it among the 'microdontic' piscivores, whose many fine teeth contrast with the 'macrodontic' group's fewer, larger teeth; they suggest this dental split reflects real ecological differences in hunting technique and in the size of prey taken, the small-toothed species perhaps gripping smaller or more slippery quarry. No stomach-content study of falcatus has been published, so the diet is inferred from form rather than observed directly; FishBase's modelled trophic level of about 3.4 is consistent with a mid-level predator. In a flock where a fifth of the species may be piscivorous, fine partitioning of this kind is how a dozen fish-eaters coexist on one lake.
Mating
No courtship or social behaviour has been recorded for Haplochromis falcatus specifically — it has only ever been studied as preserved museum material. What can be said rests on the biology of the East African haplochromine flock to which it belongs, a radiation in which the reproductive pattern is strikingly uniform. These cichlids are polygynous maternal mouthbrooders: there is no lasting pair bond. Ripe males develop bright nuptial colour — in falcatus the olive-green body with its orange-red fore-flank — and the rows of yellow eggspots on the anal fin, and they court passing females with lateral displays and quivering, typically over a small patch of substrate. Males of related species may hold loose, shifting territories during the breeding period; females visit, spawn, and depart to brood alone. The sharp colour difference between display males and cryptic females in falcatus is the visible signature of exactly this system, even though the courtship itself has not been watched in this particular fish.
Breeding
Breeding has not been documented for Haplochromis falcatus in the wild or in captivity; like its mating behaviour, it is inferred from the consistent reproductive biology of the East African haplochromines. The species is, on that basis, a maternal mouthbrooder. After spawning, the female takes the fertilised eggs into her mouth and broods them there through hatching and the early free-swimming stage, releasing fully-formed fry that she may continue to shelter in her mouth when danger threatens. The anal-fin eggspots seen on males are part of the classic mechanism: the female, snapping at what look like stray eggs on the male's fin, draws his milt into her mouth and so fertilises the clutch she is already carrying. No clutch count exists for falcatus, but small haplochromines of its size typically brood modest clutches on the order of a few dozen eggs — congeners in these lakes commonly carry roughly 20–60 — a low fecundity offset by the high survival that mouthbrooding buys. Parental care is entirely maternal and ends not long after the fry are released. These figures are genus-typical expectations, clearly labelled as such, not measurements from this species.
In the aquarium
Haplochromis falcatus is, for all practical purposes, not an aquarium fish. It is a recently described, narrow-range endemic known only from scientific collections on Lake Edward, a lake with no ornamental fishery, and it is not in the hobby or the trade. There is no body of keeping experience to report, and this section says so plainly rather than inventing husbandry. Any hypothetical care would follow the well-understood template for East African haplochromines: hard, alkaline water (pH around 8–9) at roughly 75–81 °F, a long tank with open swimming room over sand, and — because this is a piscivore — only robust tankmates too large to be eaten, never small fish or fry. Mouthbrooding haplochromines are otherwise straightforward to spawn in captivity when a species does enter the hobby, but falcatus has not, and prospective keepers are far more likely to encounter its undescribed Lake Victoria relatives (the various 'Haplochromis' trade forms) than this Edward endemic. Treat any fish sold under this name with scepticism: the identification is almost certainly wrong.
Conservation
The IUCN Red List has not evaluated Haplochromis falcatus — unsurprising, given that the species was only described in 2022 and the global cichlid assessment that covers many of its lake-mates predates it. Its status is therefore Not Evaluated, and it carries no CITES listing. That absence of a formal assessment should not be read as reassurance. Lake Edward, like the wider East African rift, faces real and rising pressure: heavy and partly unregulated fishing, catchment deforestation and erosion, agricultural and human-waste runoff, and the looming prospect of oil exploration in and around the lake within the Greater Virunga protected landscape. The Lake Victoria flock — to which Edward's haplochromines are closely allied — suffered one of the most severe vertebrate extinction episodes on record after the Nile perch was introduced; no comparable introduced predator dominates Edward, which has spared its endemics that particular fate so far, but the flock's narrow ranges leave little margin. A species known from a single lake, undescribed until recently and unstudied in life, is exactly the kind of fish that can decline before anyone has assessed it. A targeted Red List evaluation, and basic fieldwork on its ecology, are the obvious next steps.