Cichlid Atlas — the world's cichlid waters, in depth

Taxonomy & naming

The species was described by the Belgian ichthyologist Max Poll in 1944 as Haplochromis straeleni, honouring Victor Van Straelen, director of the Musée du Congo Belge at Tervuren from 1926 to 1954. It was later moved to the genus Astatoreochromis Pellegrin, 1904 — a name built from Greek roots meaning, loosely, "unstable river chromis," a fitting label for a riverine haplochromine that wanders the margins of a lake.

For decades a second nominal species, Astatoreochromis vanderhorsti (Greenwood, 1954) from the Malagarazi, was recognised alongside it. The most thorough modern treatment — Banyankimbona, Vreven & Snoeks's 2013 revision of the genus in the European Journal of Taxonomy — examined 185 specimens and synonymised vanderhorsti with straeleni, concluding the Malagarazi fish were simply A. straeleni. That revision is the backbone of the taxonomy used here, and it leaves the genus with just two valid species: the widespread, lake-flock A. alluaudi of the Victoria–Edward–Kyoga region, and this Tanganyika-basin endemic. Trade and field guides call it the "bluelip haplo"; Burundian and Tanzanian fishers fold it into generic local names for haplochromines ("Ifuro," "Ikijori," "Inunge").

Appearance

This is a small-to-medium cichlid with a moderately deep, slightly compressed body and a pointed snout. The 2013 revision records a maximum of 111.3 mm standard length (about 4.4 in) — the holotype of the old "vanderhorsti" — while FishBase lists 13 cm SL (about 5 in) and biotope sources quote roughly 12 cm (4.7 in) total length. In short, expect an adult of four to five inches, with most museum material smaller.

Live fish are dark grey-yellow above, shading to orange-yellow on the gill cover, cheek, chest and belly. The diagnostic touch is the iridescent blue wash on the lips and lower cheek that gives the bluelip its name. Fins are orange-yellow, the dorsal edged in red toward the rear, and the anal fin carries three to five horizontal rows of bright orange-yellow egg-spots (ocelli) — many more, and in more rows, than a typical riverine 'Haplochromis'. Sexual dimorphism is weak by cichlid standards: females show the same ocelli, only smaller, and the sexes differ little in colour or finnage. Coloration also tracks the water — fish from high-conductivity, muddy swamp water near the lake run darker than those from clearer upstream pools. Against its only congener, A. straeleni is told apart by its anal-fin spine count: 3–4 (usually 3) versus 4–7 (usually 5–6) in A. alluaudi, with 16–18 dorsal spines versus 17–19.

Range & habitat

Astatoreochromis straeleni is endemic to the Lake Tanganyika basin, but it is fundamentally a river-and-swamp fish rather than a lake fish. Confirmed records come from the Rusizi (the inflow on the Burundi–DR Congo border), the Lukuga (the lake's outlet to the Congo), the Malagarazi and its affluents, and the small Luiche River near the Malagarazi delta — spanning Burundi, the Democratic Republic of the Congo, Tanzania and Zambia. It does enter Lake Tanganyika proper, but only at the edges: specimens have been taken in the harbours of Bujumbura and Ujiji (near Kigoma), essentially at river mouths.

In the field it favours clear, slow water with submerged and marginal vegetation — the swampy flooded zones of the Gatumba marshes near the Rusizi mouth, vegetated stretches of small Malagarazi tributaries, and quiet swamp pools. It is notably absent from the main channels of the larger rivers and from the open rocky lakeshore that defines the classic Tanganyika cichlid biotope. The IUCN places it in shallow water, roughly 0–2 m, over muddy and sandy bottoms. So while it shares an address with Tropheus and the featherfins, it lives a very different life: a wetland generalist on the basin's soft-bottomed fringe.

Ecology & diet

The genus Astatoreochromis is best known as a mollusc specialist, and A. straeleni carries the equipment for it: a triangular lower pharyngeal jaw whose central tooth rows mix molariform (flattened, crushing) and enlarged cuspidate teeth, with slimmer pointed teeth along the margins — a mill for cracking snail shells. Greenwood reported the Malagarazi fish feeding mainly on snails, ostracods and insects, and gut contents examined in the 2013 revision bore this out: snails (whole and crushed) alongside insect fragments and other invertebrate remains, with some individuals instead packed with debris, sand and plant fragments. IUCN's assessment summarises it as omnivorous but mainly carnivorous.

The honest reading is "durophagous omnivore": a fish built to crush hard-shelled prey but flexible enough to take insects, crustaceans and plant matter as conditions dictate. (It is worth flagging a common conflation — the dramatic, diet-induced plasticity of the pharyngeal mill documented in laboratory work belongs to its congener A. alluaudi; that specific experimental story should not be transferred wholesale to straeleni.) FishBase places it around trophic level 3.4. In the basin's wetlands it functions as a mid-level invertebrate predator, and it is rarely abundant — even where it occurs it tends to turn up in ones and twos rather than schools.

Behavior & breeding

Like the rest of its genus, A. straeleni is a maternal mouthbrooder: the female takes the fertilised eggs into her mouth and incubates them there, releasing fully formed, free-swimming fry that she guards briefly afterward. The 2013 revision found females with ovarian eggs at varying stages — the most advanced, near-spawning eggs measuring 1.9–2.6 mm in diameter — and mouthbrooding females with empty guts (they fast while holding). The pattern of egg development across collecting months suggests spawning concentrated at the start of the short dry season, around December to January, though whether that is the only breeding window is unresolved.

Day to day this is not the high-strung, hyper-territorial Mbuna template. It usually occurs as scattered pairs rather than dense aggregations, and biotope keepers describe it as generally peaceful, with territoriality flaring mainly around spawning. The many-rowed anal ocelli play the usual haplochromine role in mouthbrooding courtship, and because sexual dimorphism is muted, sexing resting fish by eye is genuinely difficult.

In the aquarium

Be honest from the outset: this fish is essentially absent from the ornamental trade. The IUCN states plainly that it is not in the aquarium trade, and you will not find it on retail lists; specialist Tanganyika collectors occasionally encounter wild-caught "Malagarasi" or "Ruzizi River" stock, and that is about it. So care guidance here is extrapolated from its biology and from biotope keepers, not from a deep hobby literature.

What the natural history implies is straightforward. This is a soft-water-margin, hard-alkaline-basin fish that wants Tanganyika-style chemistry (alkaline, high-mineral, low-20s °C / 24–28 °C in the wild) but a riverine-swamp aquascape rather than a rock wall: a sand or fine-gravel bottom, generous planting or root and leaf cover, open swimming space, and calm, gently moving water. A tank on the order of 50 gallons (around 200 L) suits a small group. It is not a beginner showpiece — it is a plainly coloured, hard-to-source oddity for someone specifically interested in Tanganyika's non-lacustrine haplochromines. As a snail-crusher it is happiest with snails, frozen and live invertebrates and quality prepared foods, and pairs it with peaceful-to-moderate tankmates of similar needs. The most common mistake would be expecting it to behave, or to be available, like a typical rift-lake cichlid; it is neither.

Conservation

Astatoreochromis straeleni was reassessed for the IUCN Red List in 2025 (assessor C. Sibomana) and listed as Least Concern, carrying forward the same category it held in 2006. The rationale: it is a basin endemic of streams, swamps and river mouths, and while real threats exist, there is no evidence of declines steep enough to warrant a threatened listing. Its population size and trend are simply unknown — it is rarely taken even in frequently fished waters, and tends to occur as scattered pairs. The threat IUCN does flag is habitat degradation from watershed erosion and sedimentation driven by expanding agriculture; collection pressure is essentially nil, since the fish is eaten only locally and is not in the ornamental trade.

That species-level calm sits inside a basin under genuine strain. Lake Tanganyika has warmed measurably, and stronger, more persistent stratification has reduced deep mixing and the nutrient upwelling that fuels the food web: O'Reilly and colleagues (2003, Nature, doi:10.1038/nature01833) linked this warming to roughly a 20% drop in primary productivity and an estimated decline of around 30% in fish yields. Paleoecological work by Cohen and colleagues (2016, PNAS, doi:10.1073/pnas.1603237113) documented warming-driven losses of oxygenated benthic habitat and declines in commercial fishes and endemic molluscs. Those pressures bear most directly on the lake's pelagic clupeid (Stolothrissa, Limnothrissa) and Lates fishery that feeds four nations, and on deep- and rock-dwelling endemics — and the basin's shoreline and wetlands face added sedimentation as catchments are cleared. A. straeleni's exposure runs through that last channel: as a soft-bottomed wetland and river-mouth fish, it is most vulnerable to siltation and the degradation of marginal swamp habitat, exactly the threat IUCN names, rather than to the open-water productivity collapse. Management of the lake is shared across Burundi, the DRC, Tanzania and Zambia under the Lake Tanganyika Authority. The accurate summary is the careful one: the species itself is Least Concern, but the lake it belongs to is not without trouble, and the wetlands this particular fish depends on are the part of the basin most easily lost to erosion.

Astatoreochromis straeleni

About this species