Taxonomy & naming
Coptodon flava was described in 1992 by Melanie L. J. Stiassny, Ulrich K. Schliewen and Wallace J. Dominey as Tilapia flava, in their landmark paper 'A new species flock of cichlid fishes from Lake Bermin, Cameroon' (Ichthyological Exploration of Freshwaters 3(4):311–346). That single paper erected eight new Tilapia from this one crater lake at once — flava among them — and formalised what Schliewen and colleagues had announced in Nature in 1994 as a monophyletic radiation. The holotype (AMNH 98264) and an extensive paratype series (held at the American Museum of Natural History, the Royal Museum for Central Africa in Tervuren, and the Zoologische Staatssammlung München) all come from Lake Bermin itself, at roughly 5°09′N, 9°38′E in the Nguti subdivision of what was then South West Province. The sprawling genus Tilapia has since been dismantled: Dunz and Schliewen, in their 2013 molecular phylogeny of the haplotilapiine cichlids 'formerly referred to as Tilapia', moved the West- and Central-African substrate-brooding lineage into the resurrected genus Coptodon, placing the species in the tribe Coptodonini. The combination Coptodon flava (Stiassny, Schliewen & Dominey, 1992) is the currently valid name, though databases differ on grammatical gender, so the species also appears as Coptodon flavus. No synonyms beyond the original Tilapia combination exist.
Morphology
This is a small cichlid: FishBase records a maximum of 3 in standard length, and the lake's confined, food-limited setting keeps all nine Bermin Coptodon modest in size. The body is the typical deep, laterally compressed tilapiine form, and the defining feature is captured in the name — a yellow to golden ground colour, from which 'flava' (Latin for yellow) derives. Fin counts in the original description run to about 15 dorsal spines and 11 dorsal soft rays, with 3 anal spines and 7–8 anal soft rays. What separates flava from its lake-mates is the feeding apparatus: the diagnosis emphasises a robust lower pharyngeal jaw bearing a large, non-heart-shaped tooth plate covered with stout, sparsely arranged teeth, fine oral dentition with obliquely truncate outer-row teeth, and markedly reduced anterior gill rakers. These are the kinds of fine trophic differences that let nine related cichlids partition resources within one small lake. Sexual dimorphism in the Bermin flock is subtle and largely confined to breeding condition rather than fixed colour differences, with ripe females rounder-bodied and pairs taking on heightened spawning coloration.
Habitat
Coptodon flava is endemic to Lake Bermin (also spelled Barombi-ba-Kotto's neighbour group), a small volcanic crater lake in the western highlands of Cameroon. The lake is tiny — roughly 700 metres in diameter and only about 14.5 metres at its deepest — set within the Western Equatorial Crater Lakes freshwater ecoregion, a cluster of Cameroonian crater lakes famous for extraordinarily high fish endemism (as much as three-quarters of their fish faunas are found nowhere else). Bermin has a surface outflow but no inflowing river, which is part of what makes its cichlids so evolutionarily interesting: the lake is effectively a sealed island of water. The water is warm and tropical, consistent with low-elevation equatorial crater lakes, with pH in the broadly circumneutral range (roughly 6.5–8.0) and temperatures around 75–86 °F. Within this small basin Coptodon flava occupies the shallow littoral zone; it spawns at depths of just one to two metres, and the whole inhabited layer sits above the lake's oxygen-poor, organically loaded deep water.
Feeding
FishBase places Coptodon flava low on the food web, at a trophic level near 2.7, and reports it as feeding primarily on phytoplankton while also taking higher plants and even freshwater sponges. That browsing, herbivore-leaning diet is typical of the Coptodon (formerly Tilapia) lineage, which as a group are substrate-grazing omnivores rather than predators. The species' robust lower pharyngeal jaw with its stout, widely spaced teeth is the hallmark of a fish built to crush and process tougher plant and sessile-invertebrate material, and the reduced anterior gill rakers fit a diet of relatively large, attached food items rather than fine filter-feeding. Within Lake Bermin's nine-species flock, such differences in jaw architecture and gill-raker form are exactly the trophic specialisations that allow the related cichlids to divide the lake's limited food among themselves.
Mating
Unlike the mouthbrooding tilapias most aquarists know, Coptodon flava is a pair-bonding, substrate-spawning cichlid. Reproduction is built around a monogamous pair that forms a bond, selects and defends a spawning site, and cooperates in raising the brood. In Lake Bermin the spawning sites are pieces of sunken wood in shallow water, and the pair establishes a territory around its chosen log. Remarkably, the species has been observed spawning in loose colonies: aggregations of roughly ten pairs, with neighbouring pairs spaced about 12 in apart, each tending its own site. Pairs have even been seen jointly defending juveniles, which the original describers suggested may hint at cooperative brood care between pairs — an unusual social wrinkle for a substrate-spawning cichlid and a behaviour worth keeping in mind when interpreting the species' dense, small-lake population structure.
Breeding
Coptodon flava is a biparental, open substrate (open-brooding) spawner: the pair deposits a clutch of eggs onto a hard surface and both parents guard and tend it, rather than carrying the eggs in the mouth. In the wild the eggs are normally laid on sunken pieces of wood at depths of about one to two metres. Both parents share guarding and brood care, fanning and defending the developing eggs and then shepherding the free-swimming fry. Stiassny, Schliewen and Dominey's field observations of colonial spawning — about ten pairs nesting some 12 in apart, with adjacent pairs occasionally defending juveniles together — point to dense, socially structured breeding aggregations within the small lake. No precise wild egg count is published for this species, but substrate-brooding Coptodon are typically moderately fecund, laying clutches on the order of several hundred eggs per spawning, far more than the small broods of mouthbrooding tilapias. The species has high estimated resilience (population doubling time under 15 months), consistent with a productive open-substrate spawner.
In the aquarium
Coptodon flava is essentially never seen in the aquarium hobby. It is a tiny-range crater-lake endemic, Critically Endangered, of no food-fish or ornamental significance, and it is not bred or traded the way the commercial tilapias or the Rift-lake cichlids are; any aquarium contact has been through scientific collection and study rather than the trade. Were it kept — as its close relatives in the broader Coptodon group sometimes are — the husbandry would follow the substrate-spawning tilapiine template: warm water (about 75–86 °F) at a near-neutral to slightly alkaline pH (roughly 6.5–8.0), a mature, well-filtered tank, and an open bottom with hard surfaces such as flat stones or driftwood to serve as spawning sites. As biparental substrate spawners these fish form territorial pairs and can be aggressive around a nest, so they need space and the option to retreat from one another, and a herbivore-leaning diet (algae, vegetable matter, and a quality plant-based prepared food) suits their phytoplankton-and-plant natural diet better than a meaty one. The honest summary, though, is that this is a fish to read about rather than keep: its conservation status and pinpoint range mean responsible interest lies in protecting Lake Bermin, not in stocking a tank.
Conservation
The IUCN Red List assesses Coptodon flava as Critically Endangered (criteria B1ab(iii)+2ab(iii)), assessed by T. Moelants on 16 February 2009. The reasoning is geographic: the species exists in one lake of roughly 700 metres' diameter and nowhere else, so any degradation of that single water body threatens the entire global population. The documented pressures are oil-palm plantations and slash-and-burn agriculture in the surrounding crater rim, which drive sedimentation and pollution into the lake, compounded by deforestation. There is also a more dramatic latent hazard specific to these Cameroonian crater lakes: like nearby Lake Nyos and Lake Barombi Mbo, a stratified crater lake can hold a deep layer of CO2-charged, oxygen-poor water, and clearing the forested rim could increase wind-driven mixing that overturns the lake — an event that would flood the shallow inhabited layer with deoxygenated water and could kill the fish outright. Because all nine of Bermin's endemic Coptodon share this one basin, the flock as a whole — not just Coptodon flava — rises or falls with the health of the lake. The species carries no CITES or CMS listing; protection depends entirely on safeguarding the Lake Bermin catchment.