Taxonomy & naming
Coptodon bakossiorum was described in 1992 by Melanie L. J. Stiassny, Ulrich K. Schliewen and Wickham J. Dominey as Tilapia bakossiorum, one of eight new tilapias named in their landmark paper 'A new species flock of cichlid fishes from Lake Bermin, Cameroon' (Ichthyological Exploration of Freshwaters 3: 311–346). The holotype (ZSM 27636) and paratypes were collected from Lake Bermin in the Nguti subdivision of what was then South-West Province, at roughly 5°09′30″N, 9°38′E. For most of the next two decades the species was carried under the catch-all genus Tilapia, but molecular and morphological work steadily dismantled that assemblage: Dunz and Schliewen's 2013 revision of the haplotilapiine cichlids 'formerly referred to as Tilapia' resurrected the genus Coptodon Gervais, 1853 for the West and Central African substrate-spawning tilapiines, and bakossiorum has been placed there since. The Lake Bermin flock — bakossiorum together with Coptodon bemini, Coptodon bythobates, Coptodon flava, Coptodon gutturosa, Coptodon imbriferna, Coptodon snyderae, Coptodon spongotroktis and Coptodon thysi — is one of the textbook cases of cichlid radiation within a single small lake; phylogenetic studies (Schliewen et al. 1994; Martin et al. 2015) trace the assemblage to a riverine Coptodon ancestor allied to Coptodon guineensis, though later work has shown the histories of these crater-lake radiations to be more reticulate, with episodes of gene flow, than the original tidy sympatric-speciation story implied.
Morphology
Coptodon bakossiorum is a small cichlid, reaching about 3 in in standard length — modest even by the standards of the Bermin flock, whose members run from roughly 2–7 in. The body is the deep, laterally compressed, generalized tilapiine shape. Fin counts run to 15–16 dorsal spines with 10 soft rays, and 3 anal spines with 7–8 soft rays. The species is set apart from its lake-mates mostly by its mouth and dentition: the lips are markedly hypertrophied, and the ventral margin of the lower lip is folded and fringed, while the outer row of the jaw carries roughly 10–15 stout, bicuspid teeth and the lower pharyngeal jaw is robust, bearing a large, non-heart-shaped tooth plate covered with stout, sparsely arrayed teeth. The snout is small and projecting and the anterior gill rakers are not noticeably reduced. The most striking feature is seasonal: in breeding condition the base colour is pale yellow over the back, brightening to a vivid reddish-pink along the belly and snout, with the cheek, chin, chest and gill cover flushing an even more intense red. Outside the breeding season the fish are far plainer, and because the nine Bermin species are superficially similar and overlap in size, reliable identification rests on the combination of lip structure, tooth form and breeding colour rather than on any single obvious mark.
Habitat
The entire world range of Coptodon bakossiorum is Lake Bermin (also spelled Bermin or Bemin), a small crater lake set in the volcanic uplands of southwestern Cameroon, in the Cross–Sanaga lowland region near the Mungo drainage. The lake is genuinely tiny — on the order of 60 hectares of surface and a little over 600 metres in diameter — and shallow for a crater lake, with a maximum depth of roughly 48 ft. It is fed by no inflowing rivers and drained by a single small outlet stream, which leaves the flock effectively sealed inside one basin. Because the lake is shallow it does not accumulate the deep reservoirs of dissolved gas that make some Cameroonian crater lakes (such as Lake Nyos) prone to catastrophic limnic overturns, but the same shallowness and small volume make the system as a whole acutely vulnerable to disturbance. Recorded conditions are warm and only modestly mineralized: surface water around 75 °F, a pH near 7.5 and low alkalinity. Coptodon bakossiorum is a benthopelagic fish of these littoral waters, living among submerged wood and the sponge-and-algae-coated substrates that characterize the lake bottom.
Feeding
Like most of its lake-mates, Coptodon bakossiorum is fundamentally a herbivore and detritivore — FishBase places it at a trophic level near 2.7. The species clearly prefers plant material but also takes detritus, phytoplankton and, notably, the freshwater sponges that grow in Lake Bermin. That sponge-eating is one of the curiosities of the flock: sponges are reinforced with glassy silica spicules and offer little nutrition, and one congener (Coptodon spongotroktis) has specialized on them almost entirely, but several Bermin species including bakossiorum will graze them opportunistically. The fringed, hypertrophied lips and coarse bicuspid teeth are well suited to rasping aufwuchs — the film of algae, diatoms, detritus and small invertebrates — from submerged wood and other hard surfaces. What makes the flock biologically remarkable is how little the diets actually diverge: eight of the nine species feed in broadly the same way on broadly the same foods within the same small lake, which is part of why the Bermin radiation has been so heavily studied as a case where dramatic speciation occurred without obvious trophic partitioning.
Mating
Coptodon bakossiorum is a pair-bonding, substrate-spawning cichlid in the classic tilapiine mould. Rather than forming harems or lekking, a male and female establish and defend a shared territory, and the bond is centred on a chosen spawning site. The species is socially tolerant for much of the year — the Bermin Coptodon shoal together without serious strife — but reproduction sharpens that temperament considerably, and breeding pairs become assertively territorial toward intruders. In the wild and in captivity the pre-spawning phase involves the pair selecting and cleaning a site, with the intensifying red breeding dress signalling readiness. Sexual dimorphism is otherwise weak: the sexes are similar in size and shape, and ripe, courting fish are most easily told apart by the female's fuller belly and by behaviour at the nest. This combination of an essentially peaceful disposition that flips to determined territoriality at spawning is typical of the small Coptodon and is the single most important thing for a keeper to anticipate.
Breeding
Coptodon bakossiorum is a biparental, open substrate spawner. In Lake Bermin pairs prefer to lay in pits or shallow cavities, often in or against submerged wood; the eggs are deposited in a comparatively small cluster — on the order of about 30 eggs — onto the cleaned surface. Parental roles divide along the usual tilapiine line: the female stays close to tend and guard the eggs and larvae while the male patrols and defends the wider territory, and both parents continue to shepherd the free-swimming fry. As a small fish it matures young and at a small size; observations across the Bermin flock in aquaria record females spawning when only a few centimetres long, and the fish prove to be diligent, capable parents from their first attempts. In captivity the open-water spawning of the wild often shifts toward more sheltered sites: keepers report pairs choosing flowerpots, ceramic caves or other hidden spots rather than an exposed pit. The fry are easy to start once free-swimming, taking newly hatched brine shrimp and fine powdered foods, and grow quickly enough to be sexually mature themselves within about half a year.
In the aquarium
Lake Bermin Coptodon, bakossiorum among them, are well established as CARES Preservation Program fish and are kept by African-cichlid specialists precisely because their wild future is so precarious; the hobby population is a genuine conservation asset. They are not difficult to keep. Because they are small but a little scrappy, a tank around 35.5 in long is a sensible minimum, and the standard advice is to start with a group of six to eight juveniles and let pairs form. Outside of breeding they are not aggressive toward other species and mix well with robust, mid-sized dither fish that share their warm, slightly alkaline water — African tetras, larger barbs, rainbowfish. The critical caveat is spawning: a pair that goes to nest becomes fierce, and in anything but a very large, heavily structured tank it is best to move the other fish out (or have a divider ready), since defending parents will otherwise clear the territory themselves. Aquascape with driftwood, rockwork, caves and overturned flowerpots to break sight-lines and give subordinate fish refuge.
Water parameters need not be extreme — the wild lake sits around 75 °F with a pH near 7.5 and low hardness, and these adaptable fish do well across a moderate range so long as the water is clean and stable. Large, regular water changes (50 percent weekly to fortnightly) plus good mechanical and biological filtration suit them; one quirk worth knowing is that several Bermin species, conditioned by a lake full of edible sponges, will graze on synthetic sponge filters, so canister or hang-on-back biofiltration is the safer choice. Feeding is straightforward and is the one area where keepers most often go wrong: these are herbivores, and a vegetable-based diet — a quality spirulina or mbuna-type pellet, blanched greens, peas, and the duckweed and plant trimmings they relish — should form the bulk of the menu, with live or frozen foods given only as an occasional treat. Persistent high-protein, carnivore-style feeding is detrimental over time. Live plants are eaten rather than admired; even tough Anubias and Java fern are not reliably safe.
Conservation
The IUCN Red List assesses Coptodon bakossiorum as Critically Endangered under criteria B1ab(iii)+2ab(iii) (assessed 16 February 2009 by T. Moelants, published 2010), with the population trend listed as unknown. The category follows directly from the species' geography: its entire range is a single crater lake of well under 62 mi², so both its extent of occurrence and area of occupancy fall far below the thresholds, and any decline in the quality of that one habitat threatens the whole population at once. The threats the assessment flags are the pressures bearing on Lake Bermin and its small catchment — agricultural and forestry runoff, logging and wood harvesting around the lake, and the latent geological hazard inherent to a volcanic crater. There is no CITES listing. As a point-endemic of a tiny, outlet-fed lake with no refuge population anywhere else, bakossiorum is exactly the kind of narrow-range species for which a managed captive population matters; its presence in the CARES program and in the tanks of African-cichlid hobbyists is, realistically, an important hedge against the loss of the wild stock.