Taxonomy & naming
Haplochromis bayoni was described in 1909 by George Albert Boulenger, the prolific Belgian-British ichthyologist at the British Museum (Natural History) who worked up numerous East African fish collections sent from the colonial administrations of Uganda and German and British East Africa in the early 1900s. The epithet most plausibly honours a contemporary collector or correspondent surnamed Bayon, though the specific individual and the circumstances of the dedication are not confirmed in the sources available for this article. The species was later placed by Greenwood in Prognathochromis (erected 1979, from Greek pro-, 'forward,' and gnathos, 'jaw'), a satellite genus for a group of elongate-bodied, large-jawed Lake Victoria haplochromines with piscivorous habits. Catalog of Fishes currently retains the species within the broad genus Haplochromis, as with most of the flock, pending a comprehensive phylogenetic revision.
Morphology
A verified maximum length and detailed morphometric account specific to Haplochromis bayoni are not confirmed in the sources available here — data sparse. If the historical Prognathochromis placement reflects genuine affinity, an elongate body and a pronounced, forward-projecting jaw suited to seizing fish prey would be expected, but this is inference rather than a confirmed account for this species.
Habitat
Haplochromis bayoni is endemic to Lake Victoria, the vast, shallow equatorial lake shared by Tanzania, Uganda and Kenya. Specific figures for its depth range, water temperature or pH are not confirmed in the sources available for this article; broadly, Lake Victoria's surface waters run warm and alkaline, with typical values around 73–81 °F and pH 7.2–9.0, conditions shared by essentially the entire haplochromine flock. A precise account of the ecological guild and micro-habitat this species occupies within the lake is not available here and is not asserted.
Feeding
No confirmed gut-content study for Haplochromis bayoni is available in the sources consulted here. The historical placement of this species in Prognathochromis, a genus of elongate-jawed piscivorous haplochromines, suggests a fish-eating ecology, but this reading is an inference from that genus placement rather than a documented finding for this species.
Mating
No courtship behaviour has been documented specifically for Haplochromis bayoni. As in essentially the entire Lake Victoria haplochromine flock, mating would be expected to follow the classic polygynous, lek-like pattern: males establish and defend small display territories and court passing females using anal-fin egg-spots and nuptial colour, while females range more widely and choose among displaying males, with no pair bond formed. This account is drawn from flock-wide biology rather than from direct observation of the species.
Breeding
Haplochromis bayoni is presumed, on flock-wide grounds, to be a maternal (female-only) mouthbrooder, the reproductive mode essentially universal among Lake Victoria haplochromines: the female takes the fertilised eggs into her mouth immediately after spawning and incubates them alone for roughly two to three weeks before releasing free-swimming fry, receiving fertilisation via the male's anal-fin egg-spot display. No clutch size or species-specific breeding record for H. bayoni is confirmed in the sources available here — data sparse.
In the aquarium
Haplochromis bayoni has no documented, established history in the aquarium hobby comparable to the handful of Lake Victoria haplochromines — Pundamilia nyererei among them — that entered the trade and conservation breeding programmes before or during the lake's ecological collapse. No species-specific husbandry guidance can be responsibly given for H. bayoni without better-sourced information, and prospective keepers should not assume it is available in captivity.
Conservation
The CARES Preservation Program lists Haplochromis bayoni as Critically Endangered. A specific IUCN Red List assessment for this species is not independently confirmed in the sources available for this article, but its listing sits within the best-documented modern vertebrate mass-decline event: from the late 1970s the introduced Nile perch (Lates niloticus) erupted across Lake Victoria, and over the following decade some 200 or more endemic haplochromine species disappeared or collapsed to a fraction of their former abundance. Large, piscivorous haplochromine guilds — such as the historical Prognathochromis assemblage this species was once placed in — competed directly with the much larger introduced Nile perch for the same prey base and, in some cases, fell prey to it outright, and fared especially poorly during the crash. Many species have shown partial recovery since as Nile perch numbers were fished down, but several of the flock's original species, including this one on the evidence of its Critically Endangered listing, now survive mainly through documented aquarium maintenance programmes rather than robust wild populations.