Taxonomy & naming
Haplochromis macrops was described by the Belgian-British ichthyologist George Albert Boulenger in 1911, originally as Tilapia macrops, from material gathered during Dr. E. Bayon's third collecting expedition in Uganda (1909–1910). Boulenger placed it in Tilapia, then a catch-all for African cichlids; the type series came from Bussu on Lake Victoria and from Jinja at the Ripon Falls (the lake's historic Nile outflow), Uganda. The Catalog of Fishes records the syntypes as one specimen at the Natural History Museum, London (BMNH 1911.3.3.137, ex Genoa) and material at the Museo Civico di Storia Naturale di Genova (MSNG 12928–30); Tortonese (1963) treated MSNG 12928 as the holotype. Peter Humphry Greenwood, who spent decades untangling the Victoria haplochromines, transferred the species to the genus Haplochromis (Greenwood 1960), and that combination — Haplochromis macrops (Boulenger 1911) — remains the valid name in the Catalog of Fishes and FishBase today. As with much of the Victoria flock, the modern molecular literature would distribute these species across narrower genera (macrops is sometimes assigned to Astatotilapia), but the conventional and most stable usage keeps it under the broad genus Haplochromis, and that is the heading retained here. Untangling its limits has not been trivial: Regan's 1922 revision partly confused macrops with what is now Haplochromis ishmaeli, a reminder of how easily these morphologically similar small haplochromines are conflated. Greenwood later named a separate species, Haplochromis macropsoides (1973), explicitly for its overall resemblance to macrops.
Morphology
Haplochromis macrops is a small cichlid: FishBase gives a maximum of about 3.5 in standard length, placing it among the more modest members of the flock. As the epithet announces, its defining feature is a conspicuously large eye. Boulenger's original diagnosis recorded an eye whose diameter goes about three times into the length of the head, equals the interorbital width, and considerably exceeds the least depth of the preorbital bone — an unusually big eye for a fish of its size, which is precisely what "macrops" (Greek makros, large; ops, eye) was coined to capture. Beyond the eye, it shows the standard haplochromine bauplan: a moderately deep, laterally compressed body, a single continuous dorsal fin with spinous and soft portions, and the small conical to slightly bicuspid jaw teeth typical of a generalised insectivore rather than a heavy-jawed mollusc-crusher or a long-snouted piscivore. Reliable in-life colour notes for macrops specifically are scarce in the accessible literature; like its relatives it is presumed to be sexually dichromatic, with breeding males assuming brighter, more saturated nuptial colours and dark markings while females and non-breeding fish stay a cryptic silvery-brown — the general pattern across the flock — but the published record does not document its nuptial dress in detail, and that gap should be read as a genuine data gap rather than an absence of dimorphism.
Habitat
Haplochromis macrops is endemic to Lake Victoria, the vast, shallow equatorial lake shared by Tanzania, Uganda and Kenya; FishBase bounds its range between roughly 1°N and 3°S, and habitat assessments for the lake (including the Bujagali critical-habitat review) list it among the lake's endemic haplochromines recorded across all three riparian nations. The original types came from the northern, Ugandan end of the lake near the Jinja outflow. FishBase characterises its biotope as the shallow sandy region — open, sandy-bottomed sublittoral habitat rather than rocky reefs or deep offshore water. That is notable given the big eye, which might suggest a deep- or dim-water specialist; the dietary evidence (below) instead points to a fish working the upper water column over sand. Lake Victoria is warm and only moderately mineralised: surface waters typically run about 73–81 °F with a pH on the alkaline side of neutral, broadly 7.2 to 8.5, conditions that frame the species' tolerances even though no chemistry has been published for macrops at its own collection sites. Precise depth data for the species are not documented; FishBase classes it as benthopelagic, and its shallow-sandy, surface-feeding habits place it in the upper few metres of the sublittoral, so a shallow band (roughly 0–33 ft) is the honest estimate rather than a measured range.
Feeding
The most concrete biological data on Haplochromis macrops concern its diet, and they are informative. Examined stomachs contained sub-imaginal Ephemeroptera (mayflies in their pre-adult, winged "dun" stage), with Isoptera (winged termites) and colonial blue-green algae present in a few specimens. As FishBase notes, the combination of sub-imaginal and adult flying insects plus planktonic blue-green algae — and the conspicuous absence of bottom debris in the guts — indicates that macrops feeds at the surface or in mid-water rather than grubbing through the sediment. It is, in other words, an insectivore that exploits emerging and aerial insects and incidental plankton near the water's surface, a feeding mode for which a large, light-gathering eye is a sensible adaptation. Its estimated trophic level is about 2.8, consistent with a small invertebrate-feeder. Within Frans Witte's ecological classification of the Victoria flock into trophic guilds, a surface- and mid-water insectivore of this kind sits among the insectivorous haplochromines — one of the many fine-grained feeding specialisations that let several hundred cichlid species partition a single lake.
Mating
No courtship or social behaviour has been described specifically for Haplochromis macrops, so what can be said is drawn from the well-studied biology of the Lake Victoria haplochromine flock to which it belongs. These cichlids are not pair-bonding substrate-tenders; they are polygynous maternal mouthbrooders in which the sexes meet only briefly to spawn. Breeding males typically take up a small temporary territory or display arena over the substrate, assume bright nuptial colour, and court passing females with lateral displays and quivering. Sexual selection on male colour pattern is intense across the flock and is widely thought to be a principal engine of its explosive speciation, with females choosing mates partly on hue — a mechanism that depends on clear water and is disrupted when the lake turns turbid. Whether macrops follows this template in its particulars is undocumented; it is a reasonable inference from its membership in the flock, not an observation of this species.
Breeding
FishBase records the essential reproductive fact for Haplochromis macrops directly: mouthbrooding by females. Like the great majority of the Lake Victoria flock it is a maternal mouthbrooder — after spawning, the female takes the fertilised eggs into her mouth and broods them there through hatching and the early free-swimming stage, the male providing no parental care. No clutch count has been published for macrops itself; Victoria haplochromines of its small size typically produce modest broods on the order of a few dozen eggs (commonly cited in the tens, up to roughly a hundred in larger species), a genuinely small clutch that is the trade-off for the protection mouthbrooding affords. Parental care is therefore female-only and confined to the brooding period, with the fry released to fend for themselves once they can swim and feed. Specific spawning triggers, egg counts and developmental timing for this species remain undocumented in the accessible literature.
In the aquarium
Haplochromis macrops is essentially never kept in the aquarium hobby. Unlike a handful of charismatic Lake Victoria haplochromines that have entered the trade and conservation breeding networks, macrops is a small, plainly documented insectivore with no established presence among aquarists, no commercial supply, and almost no husbandry literature of its own. Anyone who did encounter it would treat it as a typical small Victorian haplochromine: hard, alkaline water (pH roughly 7.5–8.5, moderate hardness) at about 75–81 °F, a sandy substrate suiting its natural biotope, open swimming room, and a diet emphasising small invertebrate and insect foods to match its surface- and mid-water feeding habits. As with all flock haplochromines, males are aggressive and a workable group needs one male to several females in a tank large enough to spread that pressure. None of this is a recommendation to seek the fish out — it is a wild species of conservation concern, not an established aquarium cichlid, and the realistic statement is simply that it is not part of the hobby.
Conservation
The IUCN Red List assesses Haplochromis macrops as Data Deficient (assessed 31 March 2010 by F. Witte and M.P. de Zeeuw, Version 2025-2). Data Deficient means there is not enough information on its distribution and population status to judge its risk of extinction — a common verdict for the small, taxonomically tangled members of the Victoria flock, many of which are hard to survey and easy to confuse. It carries no CITES or CMS listing. That cautious category sits against a grim backdrop: Lake Victoria's endemic haplochromine flock, once exceeding 300 species, suffered a catastrophic collapse from the 1980s onward. The introduced Nile perch (Lates niloticus), an explosively expanding predator, together with cultural eutrophication that turned much of the lake turbid and oxygen-poor, drove roughly two-thirds of the haplochromine species to disappearance or presumed extinction (documented by Witte and colleagues). Insectivores and other open-water specialists of the sublittoral — the guild macrops belongs to — were among the hardest hit, and the turbidity that disrupts the visual mate-choice central to these fishes' reproduction compounds the threat. Whether macrops persists in viable numbers is precisely the uncertainty its Data Deficient listing reflects; some Victoria haplochromines have shown partial recovery as Nile perch were fished down, but the species' specific fate is not established.