Taxonomy & naming
The Katavi mouthbrooder was described by the German ichthyologist Lothar Seegers in 1996 as Haplochromis katavi, in his monograph 'The Fishes of the Lake Rukwa Drainage' (Annales du Musée Royal de l'Afrique Centrale, Sciences Zoologiques, vol. 278). The type material was collected from the Katuma River in western Tanzania, at the edge of Katavi National Park, and the species name is a toponym honouring that park — it is probably the only Haplochromis that occurs within its boundaries. As with most members of the vast, polyphyletic 'wastebasket' genus Haplochromis, the species has since been reassessed: the Cichlid Room Companion and several recent treatments list it as Astatotilapia katavi, placing it in the tribe Haplochromini within the subfamily Pseudocrenilabrinae. We retain the original Haplochromis heading because that is how the name is still indexed in FishBase and the Catalog of Fishes, but readers should understand the modern genus to be Astatotilapia. Seegers' 1996 revision recognised an endemic flock of six Haplochromis species in the Lake Rukwa basin (alongside a parallel six-species flock of the catfish genus Chiloglanis); Haplochromis katavi is one of these. The Lake Rukwa drainage has had recent geological connections to the Malagarasi system, to the Chambeshi (which drains to Lake Bangweulu), and to headwaters of rivers now flowing into Lake Tanganyika, and these former links are thought to have shaped the basin's haplochromine fauna.
Morphology
Haplochromis katavi is a small cichlid, reaching about 4 in in total length — a size typical of riverine and small-lake haplochromines and far short of the larger Rift-lake 'haps.' FishBase records a maximum of 4 in TL from Seegers' original material. The body is the generalised, moderately deep and laterally compressed haplochromine form, with a single dorsal fin combining spiny and soft portions and a rounded to slightly emarginate caudal fin. Like other members of its tribe the species is sexually dichromatic: nuptial males develop the brighter ground colour and bear the egg-spot-style ocelli (anal-fin 'dummy eggs') characteristic of haplochromine courtship, while females and non-breeding fish are plainer and more cryptically coloured. Detailed live coloration and meristics are documented chiefly in Seegers' 1996 description and are not widely reproduced in the hobby literature, reflecting how seldom this fish is encountered. Beyond the size figure and the broad haplochromine bauplan, fine morphometric detail for the species remains thin outside the primary description.
Habitat
The Katavi mouthbrooder is endemic to the Lake Rukwa drainage and, within it, is restricted to the system of the Katuma River in the northern part of the basin. Lake Rukwa itself is an endorheic (closed-basin) saline lake of the Western Rift Valley, sitting at about 2592 ft elevation east of the southern tip of Lake Tanganyika; it has no outflow, so dissolved salts concentrate and its waters are sodium-rich and strongly alkaline, with a pH between roughly 8.0 and 9.0. At high water the lake forms a single body; at low levels it splits into a shallow northern basin (which can dry out completely) and a deeper southern basin reaching only about 33–49 ft. Extensive papyrus and Phragmites swamps, floodplains, river deltas and seasonal wetlands fringe the system. As a Katuma-system fish, Haplochromis katavi inhabits the rivers, swamps and floodplain habitats of the northern catchment rather than the open saline lake, and it is benthopelagic in habit. In-situ water chemistry specific to its river reaches has not been separately published, but the basin's waters are warm tropical and run alkaline; in the absence of a measured river depth profile, FishBase records no depth band and the species is best regarded as a shallow-water inhabitant of the river-and-swamp zone (on the order of 0–33 ft given the basin's bathymetry).
Feeding
No dedicated diet study has been published for Haplochromis katavi, and gut-content data are not available in the accessible literature. FishBase estimates a trophic level of about 3.3, which places it as a small generalist carnivore/omnivore — the default ecology of riverine Astatotilapia-type haplochromines, which forage opportunistically on aquatic insects and their larvae, small crustaceans and other invertebrates, occasional small fish or fry, and incidental plant and detrital material taken while feeding over soft bottoms and among vegetation. In the Katuma swamps and floodplains it would function as one of the mid-level invertebrate-feeders of the community. Any more specific dietary claim would be speculation beyond what the sources support; the trophic estimate is the honest extent of what is documented.
Mating
Like essentially all members of the East African haplochromine radiation, Haplochromis katavi is a polygynous maternal mouthbrooder, and its mating system follows the well-described haplochromine template even though it has not been documented for this species in particular. Sexually active males take on heightened nuptial colour and defend a small spawning territory, courting passing females with lateral displays and quivering. The male's anal-fin egg-spots act as a releaser during spawning: as the female lays a small batch of eggs and immediately turns to take them into her mouth, she nips at the male's ocelli, drawing milt over the clutch already in her buccal cavity and ensuring fertilisation. The system is non-pair-bonding — a single male may spawn with several females — and the female alone assumes all parental investment. These behaviours are inferred from the species' membership in the Haplochromini and from its close relatives (e.g. Astatotilapia burtoni and the Rukwa flock generally), not from direct field observation of Haplochromis katavi.
Breeding
Breeding has not been specifically documented for Haplochromis katavi in the wild or in captivity, but as a haplochromine it is a maternal (ovophile) mouthbrooder. After spawning, the female carries the fertilised eggs and then the developing larvae in her mouth (buccal cavity) for roughly two to three weeks, foregoing feeding for much of that period, before releasing free-swimming fry. Clutch sizes in small haplochromines of this body size are modest — typically on the order of a few dozen eggs (congeners of similar size produce clutches in the tens, broadly 20–60), a genus-typical figure rather than a measured count for this species. After release the fry may briefly shelter back in the mother's mouth when threatened, then disperse; there is no paternal care. No fecundity, egg size, incubation period or growth data have been published for Haplochromis katavi itself, so these figures should be read as the haplochromine norm applied to a fish of its size rather than as species-specific measurements.
In the aquarium
Haplochromis katavi is essentially never kept in the aquarium hobby. It is a small, narrowly endemic, rarely collected riverine haplochromine with no established presence in the ornamental trade and no body of captive-husbandry experience to draw on — a marked contrast to the popular Rift-lake 'haps' of Malawi and Victoria. There is, accordingly, no proven keeping or breeding protocol for the species, and any guidance is extrapolated from comparable small Astatotilapia-type haplochromines. Were it to be maintained, the relevant cues come from its home water: it is a fish of warm, hard, alkaline conditions, so a temperature in the mid-20s °C (roughly 73–82 °F) with a high pH (its native basin runs pH 8–9, so neutral-to-alkaline, well-buffered water is appropriate) would suit it, in a tank furnished with open bottom, refuges and some vegetation. As a maternal mouthbrooder it would breed along standard haplochromine lines given a male holding a small territory and several females. Because of its conservation status and rarity, however, the honest assessment is that this is a wild fish of scientific rather than hobby interest, and it should be regarded as not a candidate for general aquarium keeping.
Conservation
The IUCN Red List assesses Haplochromis katavi as Vulnerable (VU), under criterion D2, assessed on 31 January 2006 by M. Hanssens and J. Snoeks; the current listing (Red List version 2025-2) retains this category and the species has not been reassessed since. The VU D2 listing reflects a very restricted range rather than any documented decline: the species is confined to a single river system (the Katuma) within the Lake Rukwa drainage, which makes it inherently vulnerable to a localised threat even though no specific population reduction or habitat loss has been recorded. The population trend is listed as unknown, and the species carries no CITES listing. The broader Lake Rukwa basin is a closed, climatically sensitive system — its lake level fluctuates dramatically and the shallow northern basin can dry completely — so the catchment's hydrology, together with regional pressures on East African floodplains (agriculture, water abstraction, wetland alteration), forms the backdrop against which a single-river endemic like this one should be watched. None of these is documented as an active threat to Haplochromis katavi specifically; the Vulnerable status rests squarely on the narrowness of its range.