Taxonomy & naming
The species was described by the Belgian-British ichthyologist George Albert Boulenger in 1899 as Tilapia cabrae, from material collected in the coastal drainages of the Lower Congo region. For more than a century it was kept in the vast, polyphyletic genus Tilapia, the historical dumping ground for African substrate-spawning 'tilapias.' A single later name falls into its synonymy: Tilapia haugi Pellegrin, 1911, described from the Ogôoué River at Ngomo in Gabon, which Teugels & Thys van den Audenaerde (1991) recognised as conspecific. The genus Pelmatolapia itself was erected by Thys van den Audenaerde in 1969, originally as a subgenus of Tilapia; the ETYFish Project notes its etymology was never explained by the author and that it presumably blends the names of two other tilapiine subgenera he recognised, Pelmatochromis and Tilapia. The decisive change came with the molecular phylogeny of Dunz & Schliewen (2013), who dismantled the old 'Tilapia' into several genera and resurrected Pelmatolapia as a valid genus for a small clade of substrate-spawning species that includes the well-known spotted tilapia Pelmatolapia mariae. Within that framework Pelmatolapia cabrae sits among the haplotilapiine cichlids of the family Cichlidae, subfamily Pseudocrenilabrinae. FishBase follows this revised classification, citing Dunz & Schliewen (2013) as the main reference, while Eschmeyer's Catalog of Fishes records the current combination Pelmatolapia cabrae (Boulenger 1899).
Morphology
Pelmatolapia cabrae is a deep-bodied, laterally compressed cichlid built along the heavy lines typical of the substrate-spawning tilapias. FishBase reports a maximum length of about 14.5 in — given as total length by one source and as standard length by another — making it a large fish by cichlid standards, though most specimens encountered are considerably smaller. The fins carry the counts diagnostic of the group: 16 to 17 dorsal spines and 11 to 14 dorsal soft rays, with three anal spines and 9 to 11 anal soft rays. The published diagnosis emphasises a straight head profile, twelve or more gill rakers on the lower limb of the first arch, and an outer row of gracile, somewhat spatulate jaw teeth — the dentition of a fish that scrapes and crops rather than crushes. The lower pharyngeal jaw bears relatively strong teeth that do not form the felt-like pavement seen in some relatives. In coloration, adults show dark, broad vertical bars across the flanks and a scattering of small, irregular red-brown spots on the ventral scales, the latter a useful field mark separating it from congeners. As in most tilapiines, overt sexual dimorphism is limited: the sexes are similar in pattern, with ripe females rounder and heavier in the body and mature males tending to run larger and develop more produced fins, but the species is not strongly dichromatic.
Habitat
This is a fish of the Lower Guinea and Congo coastal belt rather than of any great lake. FishBase places it in the coastal zone around the Ogooué (Gabon), the Kouilou-Niari and the Chiloango drainages, extending up to the mouth of the Congo River, with further records from southern Equatorial Guinea and reports from the Bengo and Cuanza systems of Angola (the Angolan material is flagged as Tilapia cf. cabrae and may need verification). It appears in the annotated checklist of the fishes of Gabon and turns up in environmental surveys of the Kouilou-Niari basin in the Republic of the Congo. The species is classed as freshwater and demersal, living on or near the bottom of warm, lowland tropical rivers, but the Catalog of Fishes lists its habitat as freshwater and brackish, and it is recorded from estuarine and mangrove-influenced coastal waters such as those of Gabon's Akanda area — consistent with the salt-tolerance widespread among tilapiine cichlids. No comprehensive in-situ chemistry has been published for the species, but its range lies in the warm, soft to moderately mineralised coastal rivers of equatorial West-Central Africa, broadly pH 6.0 to 7.8 and roughly 72–82 °F, with the fish occupying shallow margins, channels and lagoons rather than deep open water.
Feeding
Pelmatolapia cabrae is a benthic omnivore that leans, like most tilapiines, toward a plant- and detritus-based diet. Its gracile, spatulate outer teeth and high gill-raker count are the toolkit of a fish that crops filamentous algae, browses on aquatic macrophytes, and grazes the organic film and detritus of the river bed, supplementing this vegetable staple with small invertebrates and other animal matter taken incidentally from the substrate. FishBase places its trophic level near 3.5, the mid-level position expected of an opportunistic omnivore rather than a strict herbivore or a predator. Across its range it functions as one of the larger resident grazers of the coastal-river community, and like its relatives it is hardy and adaptable in diet — a flexibility that, in the genus more broadly, has allowed some congeners (notably Pelmatolapia mariae) to become established far outside Africa. No detailed wild gut-content study specific to Pelmatolapia cabrae has been published, so this account rests on its dentition, its trophic estimate, and the well-documented feeding ecology of the tilapiine group it belongs to.
Mating
Reproduction in Pelmatolapia is the trait that most clearly sets the genus apart from the mouthbrooding tilapias of Oreochromis and Sarotherodon. Pelmatolapia cabrae is a pair-bonding, substrate-spawning cichlid: a male and female form a bond and jointly hold and defend a territory through the breeding cycle, rather than the male maintaining a lek and the female carrying eggs in her mouth. FishBase explicitly records 'probably pair bonding' and an open substrate-spawning mode with both parents guarding the brood. In practice this means the pre-spawning phase centres on the establishment and defence of a nesting site on the river bed — a cleared patch of substrate, a flat stone, or a depression — which both fish ready and guard against intruders. As in related substrate-spawners, courtship involves mutual displays and site preparation, and the bonded pair becomes markedly territorial and aggressive toward conspecifics and other bottom-dwellers as spawning approaches. Detailed ethological observations of wild courtship in this particular species have not been published; the picture is drawn from FishBase's reproductive notes and the consistent biparental, territorial breeding biology documented across Pelmatolapia and the broader substrate-spawning tilapiines.
Breeding
Pelmatolapia cabrae is a biparental substrate spawner. The eggs are deposited in the open on a cleaned surface of the river bottom — a stone, root or excavated depression — and are guarded and fanned by the parents rather than taken into the mouth; FishBase records it as an open substrate brooder with both parents tending the brood. After the eggs hatch, the pair shepherds and defends the wriggler larvae and, later, the free-swimming fry, moving them between pits and guarding them aggressively until they can fend for themselves. A species-specific clutch count has not been published for Pelmatolapia cabrae, but substrate-spawning tilapiines of this size are highly fecund: relatives such as Pelmatolapia mariae lay several hundred to a few thousand adhesive eggs per spawning, and a fish approaching 14.5 in would sit toward the upper end of that range — so a clutch on the order of hundreds to low thousands of eggs is the genus-typical expectation here, offered as a labelled estimate rather than a measured figure. Spawning in the wild is presumed to track the warm-season rains of the equatorial coast, when food and shallow margins are most abundant. The species has not been the subject of a documented aquarium spawning, so fry-development timings specific to it are not on record.
In the aquarium
Pelmatolapia cabrae is essentially a wild food fish rather than an aquarium subject: it is rarely if ever offered in the ornamental trade, and there is no body of hobbyist breeding reports for it as there is for its cousin the spotted tilapia. Anyone keeping it should treat it as a large, robust, territorial substrate-spawning tilapia and plan accordingly. Adults can approach 14.5 in, so an honest minimum for a single adult or a pair is a long tank in the range of 71 in and several hundred litres; smaller quarters will not accommodate the fish's size or the strong territoriality that comes with pair formation. Water should reflect its warm equatorial coastal-river origins — roughly 72–82 °F, pH around 6.0 to 7.8, soft to moderately hard — and because the species ventures into brackish estuaries it tolerates a little added salt, though plain fresh water suits it. A sand or fine-gravel bed with flat stones, roots and a few sturdy hiding places lets it express its digging and site-clearing behaviour; delicate plants will be uprooted or grazed. Expect a hardy, undemanding feeder that takes prepared foods, vegetable matter and live or frozen items readily, and a fish that is peaceable enough outside breeding but becomes pugnacious and space-hungry once a pair bonds — robust, similarly sized tankmates and ample room are the keys to keeping it. This husbandry outline is extrapolated from the species' wild biology and from the well-known requirements of its larger relatives, since dedicated aquarium accounts of Pelmatolapia cabrae itself are lacking.
Conservation
The IUCN Red List assesses Pelmatolapia cabrae as Least Concern (assessed 1 May 2009 by L. da Costa and T. Moelants, published 2010), with the population trend listed as unknown and no specific threats identified. The assessment reflects a relatively wide distribution along the West-Central African coast — spanning Cameroon, Equatorial Guinea, Gabon, the Republic of the Congo, the Democratic Republic of the Congo and Angola — across freshwater and estuarine habitats, with no evidence of decline at the species level. It carries no CITES or CMS listing and is considered harmless to humans; across its range it is taken as a food fish. As with much of the Lower Guinea and Congo coastal-river fauna, the broader pressures on its habitat are the familiar ones of the region — deforestation and sedimentation, expanding artisanal and commercial fishing, pollution near urban estuaries, and infrastructure such as dams and resource extraction in the coastal basins — but none of these is documented as a present, species-level danger to this adaptable and widespread cichlid.