Taxonomy & naming
Serranochromis cuanza was described in 2021 by Jay R. Stauffer Jr., Roger Bills and Paul H. Skelton in the journal Zootaxa, in a paper that simultaneously named four new Angolan largemouths — Serranochromis swartzi, Serranochromis cuanza, Serranochromis alvum and Serranochromis cacuchi — from the Cuanza and Okavango drainages and laid out a preliminary identification key for the whole genus. The holotype, an adult male of 7 in standard length (SAIAB 84888), was collected with seven paratypes (SAIAB 84791, 2–5 in) at "Posto 5" on the Cuanza River, Angola, below the Capanda Dam, by Ernst Swartz on 31 October 2007. The specific name is a noun in apposition referring to the Cuanza River, spelt as is generally done in Angola; the describers consider the species most likely endemic to the Cuanza system. No earlier names apply, so the species has no synonymy, and the Catalog of Fishes lists it as valid as Serranochromis cuanza Stauffer, Bills & Skelton 2021. The genus Serranochromis was erected by C. Tate Regan in 1920 and last revised in full by Ethelwynn Trewavas in 1964; it belongs to the African cichlid subfamily Pseudocrenilabrinae and to the serranochromine lineage of riverine haplochromines that radiated across the Zambezi, Okavango, Cunene and upper Congo systems. The describers place Serranochromis cuanza in the genus on a suite of shared characters — scale rows between the orbit and the ascending arm of the preoperculum, widely spaced unicuspid (canine-like) jaw teeth, widely separated gill rakers, and egg-spot ocelli on the anal fin. They diagnose it against its congeners chiefly by the ocelli being spread throughout the anal fin of breeding males (versus restricted to the rear membranes in Serranochromis robustus and Serranochromis jallae), its exposed rather than lip-buried teeth, an emarginate caudal fin, a short jaw (44.3–52.8 % of head length), a shallow 25-degree gape, and a combination of a relatively narrow interorbit (16.3–18.0 % HL) with a greater preorbital depth and snout length than its close relative Serranochromis swartzi. The discovery sits within a broader wave of exploration of the Angolan rivers, where drainage isolation appears to have splintered the serranochromines into many narrowly distributed species.
Morphology
This is a fusiform, laterally compressed cichlid, deepest at the start of the dorsal fin, with a triangulate head a little over a third of the standard length and a straight predorsal profile rising at about 30 degrees. The known specimens span 2–7 in SL, so the recorded maximum is about 7 in SL (the holotype) — and as a member of a genus whose larger species exceed 15.5 in, the species may well grow bigger than the modest type series suggests. The mouth is the genus hallmark: terminal, large and protrusible, the lower jaw 44.3–52.8 % of head length, armed with exposed, narrowly spaced caniniform teeth in two to three rows on each jaw, set at a shallow 25-degree gape. The eyes are large and high-set, the snout long and greater than the orbit diameter, and the caudal fin is broad, short (little more than half the head length) and emarginate. Fin counts run to XV dorsal spines and 12–14 soft rays, three anal spines and 10 anal soft rays, with 36–37 lateral-line scales and five or six rows of scales on the cheek. Coloration is muted in preservation — head and body uniformly brown, with a single thin mid-lateral band and eight or nine regular bars from the back to the lower flank — but striking in life: the sides are metallic silvery from head to caudal peduncle, the back a mixed coppery-olive, the belly white, and the iris a deep purple-charcoal to reddish around the black pupil. The upper gill cover carries a metallic golden tinge and a grey opercular spot, with metallic light blue over the exposed maxilla. The anal fin has an overall yellow cast with a greyish infusion and four or five scattered ocelli (egg spots) with lighter margins on the medial and posterior membranes — the dark-cast unpaired and pelvic fins that give the fish its "black-finned" common name. As in other mouthbrooding haplochromines, the brightest dress belongs to nuptial males; females and non-nuptial fish are plainer.
Habitat
Serranochromis cuanza is, on present evidence, a point endemic: it is known only from its type locality, "Posto 5" on the Cuanza River, Angola, below the Capanda Dam. The Cuanza (Kwanza) is the largest river running entirely within Angola, rising on the central Bié Plateau and flowing northwest to the Atlantic; the type reach lies on the middle river downstream of the large Capanda hydropower dam. No in-situ water chemistry or detailed habitat notes were published with the description beyond the collection point, so conditions are inferred from the regional setting: the middle Cuanza is a warm, tropical lowland-to-plateau river, and by the general standards of west-central Angolan rivers, suitable water would run roughly pH 6.5–8.0 at about 72–82 °F over mixed sand and rock. Whether the species is genuinely restricted to this single reach or simply under-sampled along the poorly surveyed Cuanza cannot yet be said; its sister species described in the same paper are likewise each known from one locality, and much of the Angolan river network has never been collected. The presence of the species immediately below a major impoundment is itself a note of caution, since dams alter the flow, sediment and connectivity of the very habitat a riverine predator depends on.
Feeding
No gut contents have been examined for Serranochromis cuanza specifically, so its diet is inferred from its anatomy and from the well-documented ecology of the genus. Serranochromis are the "largemouths" of south-central Africa precisely because they are ambush piscivores: the big protrusible mouth and exposed, widely spaced canine teeth are the equipment of a fish that seizes and holds slippery prey. Across the genus the larger species feed predominantly on smaller fishes, supplemented by aquatic insects, snails and crustaceans, with the diet broadening in the younger and smaller-bodied forms. FishBase places Serranochromis cuanza at an estimated trophic level of about 3.8, squarely in the predator range, a figure derived from its size and the trophic ecology of its closest relatives. In the main channel of the middle Cuanza where it was found, Serranochromis cuanza would function as a mid-sized predator working the structured edges and cover for small fishes and invertebrates — the role other Serranochromis fill in their home rivers. Until specimens are dissected, however, the precise composition of its wild diet remains an informed extrapolation rather than an observation.
Mating
The reproductive behavior of Serranochromis cuanza has not been observed; what follows is drawn from the consistent pattern across Serranochromis and the serranochromine haplochromines. These are maternal mouthbrooders, and the genus is characterised by seasonal breeding tied to the flood cycle, with spawning generally beginning around the end of the low-water period as rivers and floodplains start to fill. Males develop the bright nuptial coloration — here the metallic silver flanks, coppery back, golden opercle and anal-fin ocelli — and take a territory, courting and displaying to females rather than forming a lasting pair bond. The egg-spot ocelli on the male's anal fin are the classic haplochromine courtship device: as the female mouths at the spots she is induced to take up the male's milt, fertilising the clutch she already carries. The spread of these ocelli throughout the anal fin of breeding males, rather than only across the rear membranes as in some relatives, is one of the species' diagnostic traits and presumably figures in this courtship signalling. After spawning the male's involvement ends; parental investment falls entirely to the female.
Breeding
Direct breeding observations of Serranochromis cuanza are lacking, but its mode is not in doubt: like all Serranochromis it is a maternal mouthbrooder. The female takes the fertilised eggs into her mouth and incubates them there through hatching and the early larval stage, the brood sheltered in the buccal cavity from the egg- and fry-predators of the channel; after release the fry may continue to shelter in her mouth when threatened, a hallmark of advanced haplochromine care. Clutch size has not been measured for this species; in the genus, fecundity is genus-typical and modest by cichlid standards — on the order of tens to a few hundred relatively large eggs, scaling with female size, a trade-off inherent to mouthbrooders, which sacrifice egg number for the heavy parental protection of oral incubation. That the type series included small juveniles down to about 2 in SL alongside the adult holotype suggests local recruitment at the type reach, but no breeding phenology has been recorded; spawning is expected to be seasonal, triggered by the rising-water phase of the Cuanza's annual flood. Beyond this genus-level template, the specifics of egg number, incubation period and fry development in Serranochromis cuanza remain undocumented.
In the aquarium
Serranochromis cuanza has, to all appearances, never been kept in the aquarium. It is a very recently described fish, known from a single locality on a major Angolan river, and there is no record of it entering the ornamental trade — it should be regarded as a wild scientific subject, not a hobby species. Any husbandry guidance can therefore only be extrapolated from its larger, occasionally kept congeners, which are demanding fish. Serranochromis are robust, fast-growing predators: at the size documented for Serranochromis cuanza (and very possibly larger), a single specimen would need a long, broad tank measured in hundreds of litres, with open swimming room, a substrate of fine sand and rock matching its river channel, and structured cover of roots or rockwork. Water should be kept warm and clean — roughly 72–82 °F, pH near neutral (about 6.5–7.5), soft to moderately hard — with strong filtration and generous water changes to cope with the heavy waste load of a piscivore. It would have to be fed as the predator it is, on meaty foods, and could not be trusted with any tankmate small enough to be swallowed; like other largemouths it would likely be intolerant of conspecifics outside of breeding. None of this has been tested for Serranochromis cuanza itself, and given its conservation profile — a point endemic of an under-surveyed river already altered by a major dam — the honest position is that this is a fish to study and protect in the wild rather than to seek out for a tank.
Conservation
Serranochromis cuanza has not been evaluated by the IUCN Red List; its status remains Not Evaluated (NE), and it carries no CITES or CMS listing. That blank is itself telling: the species is known from a single locality and only eight specimens, collected on one day in 2007, so the basic data needed for a formal assessment — range, population size, trend — simply do not exist. A fish documented from one point on one river is, on the face of it, the kind of narrow-range endemic that warrants concern, though it may equally prove to be more widespread once the poorly explored Cuanza is properly surveyed. Of the four 2021 Angolan largemouths, Serranochromis cuanza carries a particular flag: its type locality lies immediately below the Capanda Dam, and large impoundments reshape the flow regime, sediment transport and longitudinal connectivity of a river in ways that bear directly on a riverine predator's habitat and prey base. The broad pressures on the Cuanza, including further hydropower and agricultural development and catchment degradation, are the backdrop against which the species' future should be read, even though none has been documented as a specific threat to Serranochromis cuanza. For now its conservation status is best summarised as genuinely unknown, pending the field survey and assessment the species has yet to receive.