Taxonomy & naming
The French ichthyologist Jacques Pellegrin described this fish in 1909 as Tilapia perrieri, in the Bulletin de la Société Zoologique de France, from material collected in Kavirondo Bay (the Winam Gulf) on the Kenyan side of Lake Victoria. The two syntypes are held at the Muséum national d'Histoire naturelle in Paris (MNHN 1909-0509 and 0510) and were catalogued by Blanc in 1962. The species was transferred to the great catch-all genus Haplochromis in the CLOFFA check-list treatment of van Oijen and colleagues (1991), and that is the combination under which it appears in the Catalog of Fishes and FishBase today. When P. Humphry Greenwood split the unwieldy Lake Victoria Haplochromis into a series of smaller genera and subgenera (1979–1980), perrieri was placed in Prognathochromis, the assemblage of slender-bodied open-water and inshore piscivores; the name is still frequently written Haplochromis (Prognathochromis) perrieri or simply Prognathochromis perrieri. Because that generic scheme has never been universally adopted — many workers retain a broad Haplochromis pending a stable phylogeny of the species flock — this atlas keeps the conservative Haplochromis heading while noting the Prognathochromis placement. It belongs to the Lake Victoria haplochromine 'superflock', one of the most spectacular and best-studied examples of explosive cichlid radiation.
Morphology
Haplochromis perrieri is a small cichlid; FishBase gives a maximum of about 2.5 in standard length, in line with the modest size of most members of the flock. As a Prognathochromis it has the slender, somewhat elongate body and pointed head typical of the lake's piscivorous haplochromines, with a fairly large, obliquely set mouth and the unicuspid, recurved teeth associated with a fish-catching diet — features that, in the related Haplochromis rex and its allies, mark out the most specialised predators of the group. Detailed live coloration was never well documented before the population crashed, and because the species is known chiefly from preserved type and museum material, much of the colour pattern is lost; like other haplochromines, breeding males would have been the more brightly coloured sex. Sexual dimorphism is therefore presumed to follow the haplochromine norm — nuptial males more intensely coloured and bearing egg-spot ('ocelli') markings on the anal fin, females and non-breeding fish a duller cryptic grey-brown — but no formal description of the dimorphism of this particular species is available, so it is inferred from the group rather than measured.
Habitat
The species is endemic to Lake Victoria, the vast, shallow East African Rift lake shared by Kenya, Tanzania and Uganda and drained northward into the White Nile. FishBase characterises it as a freshwater, benthopelagic inhabitant of the tropical lake (recorded roughly between 1°N and 3°S). The type series came from Kavirondo Bay / the Winam Gulf, a large, comparatively sheltered and turbid embayment on the lake's northeastern shore. As an inshore piscivore it would have hunted over the sub-littoral mud and sand bottoms and in the open water above them rather than on rocky reefs. No in-situ water chemistry was published specifically for perrieri; Lake Victoria as a whole is warm (surface waters around 73–82 °F), well-buffered and alkaline, with pH typically in the range of about 7.2 to 9.0 and modest hardness — the broad envelope within which the entire haplochromine flock evolved. Depth-band figures for the species are not separately documented; inshore Prognathochromis of the gulfs generally occupied the upper few metres to a few tens of metres of the water column.
Feeding
Haplochromis perrieri is a piscivore — FishBase records simply that it 'feeds on fish', and assigns it a high trophic level of about 4.2, near the top of the haplochromine range. Its placement in Prognathochromis, the genus Greenwood erected for the lake's predatory haplochromines, reflects exactly this guild: slender ambush-and-pursuit hunters of other small fishes, in practice largely of smaller haplochromines and juvenile cichlids. The recurved, widely spaced teeth and large gape of the group are the tools of a fish-grabber rather than a sand-sifter or algae-scraper. In the pre-perch Lake Victoria community these inshore piscivores were an important link converting the enormous biomass of zooplanktivorous and detritivorous haplochromines into top-predator production — a role that made them especially vulnerable when an even larger, introduced predator arrived.
Mating
No courtship or social behaviour has been described for Haplochromis perrieri specifically; it disappeared before its biology could be studied in any detail. The reproductive biology is therefore read from the wider Lake Victoria haplochromine flock, which is remarkably uniform in its mating system. These are polygynous maternal mouthbrooders: males establish and defend small territories and court passing females with displays and quivering, using the yellow-and-orange egg-spots on the anal fin as a lure. There is no lasting pair bond and no male parental care. Mate choice in the flock is strongly visual and colour-based, and the resulting assortative mating on male nuptial colour is widely thought to be one of the engines of the lake's explosive speciation — a process that, conversely, broke down in the turbid, light-poor water that followed eutrophication, blurring species boundaries.
Breeding
Like essentially all Lake Victoria haplochromines, Haplochromis perrieri is a maternal mouthbrooder, and FishBase records it simply as a 'mouthbrooder'. After spawning the female takes the fertilised eggs into her mouth and broods them there through hatching and the early free-swimming stage, releasing the fry only when they can fend for themselves and snapping them back in at any threat. The males contribute nothing beyond fertilisation. No clutch count was ever published for this species; congeneric Lake Victoria haplochromines of comparable size are small-clutch brooders, typically producing on the order of a few dozen relatively large eggs (roughly 20–60) per spawning — a low fecundity offset by the high survival that intensive oral care provides. FishBase nonetheless rates the species' resilience as high on the basis of a short estimated population-doubling time. Breeding triggers, fry development and brooding duration for perrieri itself are unrecorded.
In the aquarium
Haplochromis perrieri is not an aquarium fish in any practical sense: it is known almost entirely from museum specimens, has not been reliably collected since the 1980s, and is not present in the ornamental trade or in any documented captive population. There is consequently no husbandry tradition to report for it. A handful of Lake Victoria haplochromines have been maintained and bred by specialists and public aquaria as part of conservation 'ark' efforts, and the general recipe for the group is well understood — hard, alkaline water around pH 7.5–8.5 and 75–81 °F, a sand bottom with rockwork to break up sightlines, a strongly male-skewed harem in a generously sized tank, and a high-protein diet — but applying any of this to perrieri specifically is moot, because no stock exists. A piscivore of its build, were it ever rediscovered and kept, would need to be housed only with tankmates too large to be swallowed. For now the honest statement is that this species is effectively a museum animal, of interest to ichthyology and conservation rather than to the hobby.
Conservation
The IUCN Red List assesses Haplochromis perrieri as Critically Endangered (possibly extinct) under criterion C2a(ii), assessed on 31 March 2010 by Witte, de Zeeuw and Brooks, with a decreasing population trend; it has no CITES or CMS listing. It has not been reliably recorded since about 1986. Its decline is part of the catastrophic collapse of the Lake Victoria haplochromine flock in the late twentieth century — once several hundred species, the great majority of them endemic and many undescribed. Three forces converged: the deliberate introduction and population explosion of the predatory Nile perch (Lates niloticus), which directly consumed vast numbers of haplochromines; severe eutrophication and the spread of hypoxic deep water, which shrank usable habitat; and the loss of the clear-water light environment on which the flock's colour-based mate recognition depended, which blurred reproductive isolation between species. Inshore piscivores such as the Prognathochromis were hit especially hard, competing directly with the very predator that was eating them. Whether any perrieri survive in a refuge gulf or satellite water is unknown; the species is among the many for which the honest verdict is 'missing, presumed lost', pending targeted survey work.