Taxonomy & naming
Haplochromis cinereus was described by the Belgian-British ichthyologist George Albert Boulenger in 1906 as Paratilapia cinerea, from a single specimen collected by E. Degen at Buganga on the Ugandan shore of Lake Victoria. That holotype (the unique type, BMNH 1906.5.30.292) still rests in the Natural History Museum, London. Boulenger placed the new fish in the broad early-twentieth-century genus Paratilapia; it was subsequently transferred to Haplochromis, the catch-all genus that came to hold the bulk of the Victorian flock, and validated under that combination by P. H. Greenwood (1960) and in the CLOFFA checklist treatment of van Oijen and colleagues (1991). The species threads through the long history of Victorian cichlid taxonomy: it was variously confused with Tilapia lacrymosa and Haplochromis stanleyi in Boulenger's own catalogues, redescribed and figured by Greenwood in his multi-part Revision of the Lake Victoria Haplochromis (Part 3, 1959), and reassigned by Greenwood (1980) to the genus Astatotilapia in his attempt to break the unwieldy Haplochromis into phyletic units. That generic split has never been universally adopted, and the Atlas retains the conventional Haplochromis heading under which the fish is catalogued in FishBase and the Catalog of Fishes, while noting that Astatotilapia cinerea is the same animal. The Lake Victoria haplochromines form one of the most spectacular adaptive radiations known — several hundred closely related, very recently diverged species — and the boundaries between many of them, cinereus among them, remain genuinely difficult to draw.
Morphology
This is a small cichlid: the documented maximum is about 3 in standard length (roughly 3 in SL in Greenwood's material), making it a typical member of the flock's lower size range. The body is the moderately elongate, laterally compressed haplochromine form. Its colour is the source of the name: cinereus is Latin for 'ash-coloured', and Boulenger's fish was grey above and below — darker on the back, paler beneath — with dark grey fins, the ashen tone that distinguishes it from the many gaudier members of the radiation. As in essentially all Victorian haplochromines, the species is sexually dimorphic and dichromatic in the haplochromine manner: territorial males develop the brighter nuptial coloration and carry yolk-yellow to orange egg-spots (ocelli) on the anal fin, while females and non-breeding fish are the drab, cryptic grey that gave the species its epithet. Fine-scale diagnostic features — tooth form, head proportions, scale and fin-ray counts — are what separate cinereus from its near-relatives; like much of the flock it lacks a single dramatic external trait and is identified instead by a combination of meristics and proportions worked out in Greenwood's revisions.
Habitat
Haplochromis cinereus is endemic to Lake Victoria, the vast, shallow equatorial lake shared by Tanzania, Uganda and Kenya, and is not known from anywhere else. It is a fish of the shallow sublittoral: it occurs over sandy bottoms on both protected and exposed shores, in water generally less than about 23 ft deep (FishBase gives a depth range to 23 ft), within the warm surface band of the lake. It has been recorded across the lake from the Ugandan type locality at Buganga to the intensively studied Mwanza Gulf in the Tanzanian south, where the Dutch HEST team (Witte, van Oijen and colleagues) surveyed the haplochromine community in detail. Lake Victoria's open water is warm and well-buffered: surface temperatures typically run about 73–81 °F and the water is alkaline, with pH commonly in the range of roughly 7.2 to 9.0 and moderate hardness — the broad chemical envelope shared by the whole flock rather than figures measured for this species in particular. As a shallow sand-dweller, cinereus belonged to the inshore guild that was among the first and hardest hit when the lake's ecology was overturned in the late twentieth century.
Feeding
Examination of stomach and intestinal contents (the material reported by Greenwood) showed that Haplochromis cinereus feeds on sand grains, bottom detritus — including fragments of plant epidermis — and some larvae of dipterous (true-fly) insects, chiefly chironomid midges. This places it firmly among the detritivore / benthic-invertivore element of the Victorian flock rather than among the rock-scrapers, snail-crushers, plankton-pickers or fish-eaters into which the radiation otherwise partitioned the lake. FishBase estimates its trophic level at about 2.6, consistent with a low-level forager that works the sandy bottom, taking in sediment along with the organic detritus and small invertebrate larvae it strains from it. In the functioning pre-perch lake this guild of small sand-dwelling detritivores was numerically abundant and formed an important link converting bottom detritus and benthic insect production into prey for larger fishes.
Mating
No courtship study specific to Haplochromis cinereus has been published, but its reproductive biology follows the well-documented and highly conservative haplochromine pattern. These cichlids are polygynous: mature males establish and defend temporary territories, often on or near the sand, and signal to females with intensified nuptial colour and with the egg-spots on the anal fin. There is no lasting pair bond. A ripe female visits a displaying male, the pair circle and spawn, and the female alone takes on all subsequent parental duty. Competition among males for display sites and the female's free choice among them are the engine that, repeated across hundreds of species, is thought to have driven the explosive speciation of the Victorian flock through sexual selection on male colour — which makes the loss of clear-water visual conditions during the lake's eutrophication so damaging to these fishes.
Breeding
Haplochromis cinereus is a maternal (female) mouthbrooder, as FishBase records and as is the rule throughout the Lake Victoria haplochromines. After spawning, the female takes the fertilised eggs into her mouth and broods them there; the egg-spots on the male's anal fin are part of the spawning sequence by which fertilisation is achieved close to her mouth. She carries the developing eggs and then the larvae through to free-swimming young, not feeding while she broods, and continues to shelter the fry in her mouth at the first sign of danger for some time after they can swim. No clutch count has been published for cinereus specifically; small Victorian haplochromines of this size typically carry only modest broods — on the order of a few dozen eggs (commonly around 20–60) — a low fecundity offset by the high survival that intensive maternal mouthbrooding buys. There is no paternal care. The species has not, as far as the record shows, been bred in captivity.
In the aquarium
Haplochromis cinereus is essentially never seen in the aquarium hobby. It is a small, plainly ash-grey, scientifically obscure sand-dweller with no trade history, and it is not deliberately collected or exported; unlike the handful of brightly coloured Victorian haplochromines that circulate among specialist keepers (often as conservation 'ark' populations), cinereus has no following. Nothing here should be read as a husbandry recommendation. If it were ever maintained, it would need what the Victorian haplochromines as a group require: hard, alkaline water (pH around 7.5–8.5) at roughly 75–81 °F, an open sandy bottom suiting a bottom-forager of its feeding type, and the spacious, structured tank that the genus's territorial, polygynous males demand, with several females per male to spread aggression. Given its conservation status and total absence from the trade, the species is of interest as a wild component of Lake Victoria's imperilled flock rather than as an aquarium fish.
Conservation
The IUCN Red List assesses Haplochromis cinereus as Data Deficient (assessed 31 March 2010 by F. Witte and M. P. de Zeeuw) — the category used when there is not enough information on distribution and population to judge extinction risk, a common outcome for the many small, taxonomically difficult members of the Victorian flock. That uncertainty sits against a stark backdrop. Lake Victoria once held one of the richest assemblages of endemic vertebrates on Earth, several hundred haplochromine species found nowhere else. From the late 1970s the upsurge of the introduced Nile perch (Lates niloticus), a large predator, combined with severe eutrophication and falling water clarity, drove the collapse of this flock; quantitative trawl data from the Mwanza Gulf (Witte and colleagues) documented the disappearance of a large fraction of the haplochromine species, with estimates of 200 or more endemic taxa lost or pushed to local extinction. Inshore sand- and detritus-feeding species such as cinereus were among the guilds most exposed, being concentrated in exactly the shallow waters the perch invaded. Some haplochromines have shown a partial, altered recovery in recent decades as perch stocks were fished down, but for poorly documented species like this one the Data Deficient listing is an honest statement that its present status is simply unknown.