Taxonomy & naming
Tylochromis intermedius was described by the prolific Belgian-British ichthyologist George Albert Boulenger in 1916, in the fourth volume of his monumental Catalogue of the Fresh-water Fishes of Africa, as Pelmatochromis intermedius. The type material came from the North Sherbro District of Sierra Leone; Melanie Stiassny later selected a lectotype, BMNH 1915.5.19.22, held in the Natural History Museum, London, with a single paralectotype (BMNH 1915.5.19.23). The genus Tylochromis itself was not erected until 1920, when Charles Tate Regan revised the African cichlids of this group and raised it to genus rank with Tylochromis jentinki as its type species; intermedius was duly transferred in, and it has been treated as a valid Tylochromis ever since (Lévêque et al. 1989; Stiassny 1989; Paugy et al. 1990). Its specific status was once doubted — Schultz (1942) and Daget (1954) questioned whether it was distinct at all — but Stiassny's comprehensive 1989 monograph (A Taxonomic Revision of the African Genus Tylochromis, Annales du Musée Royal de l'Afrique Centrale 258: 1–161) retained it as a good species, diagnosed in part by its 31 vertebrae, three scale rows between the anterior parts of the upper and lower lateral lines, thin lips, and a lower jaw whose posterior end sits below the tip at a shallow 15–20° angle. Within the family, Stiassny used the whole genus to argue a larger phylogenetic point: in her 1990 study she placed Tylochromis near the base of the African cichlid radiation, well outside the haplochromine and lamprologine assemblages — an old, generalized lineage rather than a product of any of the great species flocks. Tylochromis intermedius is one of the West African coastal members of that basal group.
Morphology
Tylochromis intermedius is a robust, laterally compressed, large-scaled cichlid of the typical Tylochromis build: a deep body, a steep forehead, and a comparatively small, low-set mouth that reads at a glance as a bottom feeder rather than a midwater hunter. FishBase records a maximum length of about 10.5 in total length, placing it among the larger West African members of the genus and broadly consistent with the genus-typical figure of roughly 10 in. The fins carry 12–15 dorsal spines and 15–18 soft rays, with three anal spines and 7–9 anal soft rays. Diagnostically, Stiassny separated it on its 31 vertebrae, the three scale rows between the anterior ends of the two lateral lines, its thin lips, and the angle of the lower jaw. As in the rest of the genus, the defining hard-anatomy character is the lower pharyngeal jaw, which is well developed for processing benthic prey — though intermedius is not among the extreme snail-crushers (its congener Tylochromis mylodon, the 'mill-tooth,' holds that distinction with molariform teeth covering most of the pharyngeal plate). No reliable account of sexual dichromatism or strong size dimorphism has been published for this species specifically; in the genus the sexes are generally similar, and what differences exist tend to be subtle differences in size and buccal dentition rather than the bold colour differences of haplochromines. Live colour is undocumented in the literature beyond the silvery, large-scaled appearance typical of estuarine Tylochromis.
Habitat
The species is a fish of the West African coastal lowlands, distributed through the rivers and estuaries of the Upper Guinea coast. FishBase and the regional faunal literature give its range as coastal rivers from the Gambia south and east to the Tano River in Ghana, spanning roughly 14°N to 5°N; FishBase lists six native countries — the Gambia, Guinea, Sierra Leone, Liberia, Côte d'Ivoire and Ghana — and the range crosses the Northern Upper Guinea and Southern Upper Guinea freshwater ecoregions, reaching its eastern terminus on the Ghanaian coast. The type locality, the North Sherbro District of Sierra Leone, sits in exactly the kind of estuarine, mangrove-fringed coastal-river country that characterizes the genus's West African members. Like several of its relatives (among them the closely related Tylochromis jentinki, an explicitly brackish-tolerant estuary fish), Tylochromis intermedius occupies the lower reaches and tidal mouths of coastal rivers as well as freshwater upstream, and is part of the benthic fish community of these soft-bottomed systems. FishBase summarizes its environment as freshwater, benthopelagic, in tropical water of about 75–82 °F, pH 6.5–7.5, and soft to moderate hardness (dH from about 2 upward). Published in-situ depth measurements specific to this species are scarce; as a benthic forager of coastal rivers and estuaries it works the shallow soft bottoms — on the order of the uppermost few metres rather than any deep habitat — and a conservative documented occupied depth band of roughly 0–33 ft reflects the shallow estuarine and riverine waters it is recorded from.
Feeding
Tylochromis intermedius is, in FishBase's phrasing, an 'opportunistic benthic macrophage' — a bottom-working generalist that sifts and grubs soft sediment for invertebrates. Stiassny's revision characterized the genus as a whole as benthic macrophages inhabiting the main channels of rivers and the open inshore waters of lakes, and intermedius fits that mould: it prefers insects and their larvae, taking mouthfuls of sand and mud, winnowing the edible fraction, and processing harder items with its sturdy lower pharyngeal jaw. The genus's ecological signature is precisely this sand-sifting, bottom-grubbing trade — none of the Tylochromis are aufwuchs grazers, scale-biters or open-water planktivores in the way the rift-lake endemics are; they are sediment generalists. Among congeners the diet shades from softer insect larvae and crustaceans toward hard-shelled molluscs depending on how strongly the pharyngeal mill is developed; intermedius, lacking the extreme molariform dentition of Tylochromis mylodon, leans toward the softer end of that spectrum, with insects and their larvae the documented staple. FishBase estimates its trophic level near 2.6, squarely that of an invertebrate-feeder rather than a piscivore. In its estuarine community it functions as a roving benthic forager of the soft-bottom zone.
Mating
The reproductive biology of Tylochromis intermedius follows the consistent genus template rather than any species-specific account: Tylochromis are maternal mouthbrooders that do not form lasting pair bonds. In this system the male's investment effectively ends at fertilization — there is no biparental territory and no durable pair, in sharp contrast to the cave- and substrate-spawning lamprologines. What little is known of social structure in the genus comes mainly from the better-studied lake species: gregarious, schooling juveniles give way to more solitary, wandering adults that defend a spawning site only transiently rather than holding a permanent territory. For intermedius specifically, courtship behaviour, the details of mate choice and any seasonal spawning cues are essentially undocumented in the wild, and that gap is worth stating plainly rather than filling with inference. What is firmly established, from FishBase following Stiassny (1989) and Lamboj (2004), is the mating system itself: maternal mouthbrooding without pair-bonding.
Breeding
As a maternal mouthbrooder, the female of Tylochromis intermedius takes the fertilized eggs into her buccal cavity and incubates and guards the developing brood there until the fry are free-swimming, after which she alone continues to shelter them; the male contributes no parental care. This is the classic African mouthbrooding template shared with the haplochromines and tilapiines, and it carries the usual trade-off of relatively few, large, yolky eggs in exchange for well-developed young. Clutch sizes have not been published for intermedius itself; as a genus-typical reference point, females of the Tanganyikan Tylochromis polylepis have been observed carrying on the order of 100 large eggs (around 0.5 in in diameter), a small, well-provisioned clutch that is broadly characteristic of the genus and a reasonable expectation for a fish of this size and reproductive mode. Specific spawning triggers, incubation duration and fry development for this species are undocumented in the wild — the species has essentially no aquarium breeding record — so the honest summary is that the mode is securely known (female mouthbrooder, no pair bond) while the quantitative details remain to be described.
In the aquarium
Tylochromis intermedius is, for practical purposes, not an aquarium fish. It is a large West African coastal-river cichlid with no established presence in the hobby and no meaningful captive husbandry or breeding record; in its range it is part of the local fish fauna and a minor food fish rather than an ornamental export. Anything that can be said about keeping it is therefore extrapolated from the genus, and should be read as such. A fish approaching 10.5 in that feeds by working the substrate would need a long tank with a substantial open footprint, a deep bed of fine sand it can sift, hard work from the filtration to handle the detritus it kicks up, and — importantly — excellent oxygenation, since Tylochromis are noted for a marked intolerance of low dissolved oxygen and do badly in crowded, under-aerated tanks. Water should sit in the warm, near-neutral to slightly soft range the species occupies in the wild (roughly 75–82 °F, pH about 6.5–7.5), and given its estuarine affinities it would likely tolerate a little added salinity better than most cichlids, though there is no documented requirement for it. Diet would be a straightforward carnivore/omnivore regime of sinking foods, frozen invertebrates and the occasional vegetable matter, mirroring its natural insect- and crustacean-leaning intake. The two recurring genus-level mistakes apply: do not treat it as a small rock-dweller crammed into rockwork — it is an open-substrate roamer that needs room and sand — and do not stock it in a poorly oxygenated tank. Realistically, though, this is a fish for a public aquarium or a specialist working with West African coastal species, not a home-aquarium candidate.
Conservation
The IUCN Red List assesses Tylochromis intermedius as Least Concern, assessed on 14 January 2020 (published 2020) by H. Dankwa, T. Bousso and P. Lalèyè, reflecting a wide distribution along the Upper Guinea coast and no evidence of a population-level threat. It carries no CITES or CMS listing and is harmless to humans. That said, the regional conservation literature does not treat it as entirely without pressure: the IUCN-led review of the status and distribution of freshwater fishes in western Africa (Schmidt and colleagues) flags Tylochromis intermedius — alongside other widespread coastal-river species — as potentially overexploited where local fisheries are intensive, precisely because as a sizeable benthic fish of accessible coastal rivers and estuaries it is readily caught. The broader backdrop for the Upper Guinea coastal systems it inhabits is the familiar West African mix of habitat pressure: dam construction on coastal rivers, deforestation and sedimentation, mangrove loss in the estuaries, and growing fishing effort. None of these is documented as a present danger to this particular species, and its current Least Concern status appears well founded, but they are the context within which its long-term outlook should be read.