Taxonomy & naming
Coptodon dageti was described as Tilapia dageti by the Belgian ichthyologist Dirk F. E. Thys van den Audenaerde in 1971, in a paper presenting new data on the Tilapia species of the subgenus Coptodon. The type locality is the Volta River just below the Akosombo Dam in Ghana; the holotype (MRAC no. 155.731) and a long series of 31 paratypes are held mainly at the Royal Museum for Central Africa in Tervuren, Belgium, with additional paratypes at the Muséum national d'Histoire naturelle in Paris. The species had effectively been hiding in plain sight for decades: earlier West African workers, including Jacques Daget himself, had repeatedly recorded it under the misapplied name Tilapia melanopleura (a name now treated as a synonym of Coptodon rendalli), so much of the older literature on 'melanopleura' from the Niger and neighbouring basins in fact refers to this fish. Thys van den Audenaerde separated it on pharyngeal and meristic grounds. The substrate-spawning tilapiines were long held in a broad genus Tilapia, but the molecular phylogeny of Dunz & Schliewen (2013) showed that assemblage to be unnatural and resurrected several older genus names; their revised classification places this species in Coptodon Gervais, 1853, a clade of West and Central African substrate spawners. Catalog of Fishes and FishBase both now list it as Coptodon dageti.
Morphology
This is a moderately large tilapia. FishBase gives a maximum of about 15.5 in total length and a published weight of roughly 1 kg, though most fish encountered are well short of that. The body is the deep, laterally compressed oval typical of the substrate-spawning tilapiines, with a continuous spiny-and-soft dorsal fin carrying 14 to 16 spines and 12 to 16 soft rays (commonly around 15 spines and 13 to 15 rays), three anal spines, and 8 to 10 soft anal rays. The diagnostic characters Thys van den Audenaerde used are largely internal and proportional: the lower pharyngeal bone is about as long as broad, with the toothless anterior lamella shorter than the toothed area, and the median pharyngeal teeth are not broadened. There are 8 to 10 gill-rakers on the lower limb. In life the flanks carry a series of dark vertical bars that are bifurcated (split into two) on the upper half of the body, a useful field mark, and unlike some relatives the dorsal and anal fins lack an orange-red upper margin and the dorsal and caudal fins are at most feebly blotched. As in most Coptodon, sexual dimorphism is slight outside the breeding season; ripening fish develop heightened colour and the genital papilla differs between the sexes, and breeding males tend to be the larger and more intensely coloured.
Habitat
Coptodon dageti is a freshwater, demersal, potamodromous fish of the West and Central African savanna zone. Its documented range spans the upper Senegal, the upper and middle Niger system, the upper Comoé, the Bandama and upper Sassandra of Côte d'Ivoire, the upper and lower Volta (including the man-made Lake Kainji and the reservoir behind Akosombo), the Mono, the Bénoué (upper Niger–Benue system), and the Lake Chad basin. This places it across a swathe of Sudanian rivers and floodplains rather than in any single drainage. It is a warm-water fish: FishBase cites a temperature range of about 75–82 °F, consistent with the lowland tropical rivers, floodplain lakes and reservoirs it occupies. Across that range these are generally turbid to clear running and standing waters of near-neutral to mildly alkaline chemistry, with seasonal flooding governing much of the fish's movement and reproduction. No single in-situ chemistry profile defines the species, but the savanna rivers it inhabits typically run circumneutral, in the pH 6 to 8 band, with the fish moving onto inundated floodplain margins as waters rise. As a shallow-water, plant-associated spawner it keeps to the upper few metres of the water column rather than deep open water.
Feeding
Coptodon is the herbivorous–detritivorous wing of the old Tilapia assemblage, and Coptodon dageti fits that mould. FishBase places its trophic level low, around 2.4, the signature of a fish feeding near the base of the food web on plant material and detritus rather than on other fishes. Its close relatives in the genus, the redbelly tilapia Coptodon zillii foremost among them, are documented macrophyte-grazers that also take filamentous algae, fallen terrestrial leaves, phytoplankton and organic detritus, supplementing this with small invertebrates particularly when young. Coptodon dageti is best read as a generalist grazer-detritivore of the same kind, working vegetated margins and the soft bottom of floodplain rivers and reservoirs. In the river community it functions as a primary consumer that converts aquatic vegetation and detritus into fish biomass, which is part of why the substrate-spawning tilapias are valued in African inland fisheries and aquaculture.
Mating
Like other Coptodon, Coptodon dageti is a pair-bonding substrate spawner rather than a mouthbrooder, and its social system reorganizes around a defended nest at breeding time. FishBase summarizes its reproduction as 'probably pair-bonding, open-substratum spawner, with both parents guarding the brood.' In the better-studied congeners this means a male and female form a monogamous pair for the breeding period, become strongly territorial, and jointly clear and defend a nest site on the bottom, typically in shallow, well-vegetated water. Courtship and the bond are tied to that prepared site; the pair drives off intruders together, and the territoriality that makes these fish effective parents also makes them combative toward conspecifics and other bottom-dwellers crowding the nest. The specifics of courtship in Coptodon dageti itself have not been described in detail in the literature, but there is no indication it departs from the substrate-spawning, biparental pattern that characterizes the genus.
Breeding
Coptodon dageti is a biparental substrate spawner. In the manner of its genus, the pair excavates or clears a nest depression on the bottom in shallow water and the female lays adhesive eggs directly onto the cleaned substrate, where both parents guard and fan them through incubation and then shepherd the free-swimming fry. This open-brooding strategy contrasts sharply with the mouthbrooding tilapias (Oreochromis, Sarotherodon): the eggs and larvae are more exposed to predators, so the pair compensates with vigorous joint defence of the nest and brood. Species-specific clutch and fecundity figures for Coptodon dageti have not been published, but the substrate-spawning Coptodon are moderately fecund batch spawners; the well-documented Coptodon zillii, for comparison, lays adhesive eggs in a shallow nest guarded by both parents and can spawn repeatedly through a warm season, with clutches numbering from several hundred to a few thousand eggs depending on female size. Spawning in these savanna tilapias is tied to warmth and to the flood pulse, with reproduction concentrated when waters are warm and floodplain habitat is available. FishBase rates the species' resilience as medium, with a minimum population doubling time on the order of 1.4 to 4.4 years.
In the aquarium
Coptodon dageti is essentially a food-fish and fisheries species rather than an aquarium subject, and it has no established presence in the ornamental hobby; it is not a fish a keeper is likely to encounter for sale. Anyone who did keep it should treat it as a large, robust, plant-eating substrate-spawning tilapia and plan accordingly. At a potential 15.5 in and around a kilogram, an adult or pair needs a very large tank — on the order of a couple of metres of length and several hundred litres — with strong filtration to handle the waste load of a big herbivore. Warm water in the species' documented 75–82 °F range and near-neutral chemistry (roughly pH 6 to 8) suit it. Décor should be hardy: like its relatives it will dig and rearrange the bottom when preparing to spawn, and it will graze and uproot soft plants, so robust or potted vegetation, a sand or fine-gravel substrate it can work, and some flat rock or a cleared area as a potential spawning surface are the sensible choices. Diet is straightforward — a vegetable-based staple (spirulina or other plant-forward prepared foods), blanched greens and the like, with modest animal protein — reflecting its low trophic level. The main husbandry caution is the same territorial aggression that makes it a good parent: breeding pairs become combative, so tankmates must be large and able to keep their distance. None of this is exotic for an experienced keeper of large African cichlids, but it is a commitment-scale fish, not a community species.
Conservation
The IUCN Red List assesses Coptodon dageti as Least Concern. The current assessment was carried out on 6 October 2019 (published in the 2020 update) by Diouf, Awaïss & Laleye under the Pan-Africa freshwater biodiversity programme. The rating reflects the species' very broad distribution across multiple major West and Central African basins — Senegal, Niger, Volta, Comoé, Bandama, Mono, Bénoué and Lake Chad — and the absence of any range-wide threat severe enough to qualify it for a higher category. It carries no CITES or CMS listing and is regarded as harmless to humans. The species supports commercial food fisheries across its range, which is a use rather than, at present, a documented population-level threat. As with all wide-ranging Sahelo-Sudanian river fishes, the relevant background pressures are basin-scale: damming and flow regulation (the species' own type locality sits below the Akosombo Dam, and it occurs in the Kainji reservoir), wetland and floodplain loss, pollution, and the long-term hydrological stress of a drying climate on the Sahelian rivers and Lake Chad. None of these is flagged as an immediate danger to this particular tilapia, but they are the context in which its widespread, currently secure status should be read.