Taxonomy & naming
Otopharynx sp. "Circle" has no describing author, no publication date, and no entry under a validated name in Eschmeyer's Catalog of Fishes; it is an informal trade name, not a scientific one. The genus Otopharynx (Regan, 1920) is diagnosed largely by a melanic colour pattern of discrete dark blotches on the flank — a suprapectoral spot, a supra-anal spot and a caudal-peduncle spot in the clearest cases — and single-word trade names describing a particular marking, such as "Circle," are a common way of labelling an undescribed local form by its most conspicuous field character. No published study has established which described Otopharynx species this Nkhotakota population is most closely allied to, and it should be treated as a distinct, unresolved entity pending that work.
Morphology
As implied by its trade name, this form is presumed to carry a ring-shaped or circular marking, most likely on the flank, distinguishing it from Otopharynx forms with plainer or differently shaped blotches. Beyond that inferred colour cue, no formal morphometric study has been published for this population. The body should be expected to follow the moderately deep, laterally compressed shape typical of the genus, with genus-typical size for a mid-sized Otopharynx running to roughly 4.5–6 in total length. Sexual dichromatism is expected on general Malawi cichlid grounds, with breeding males more strongly and contrastingly marked — including, per the trade name, the circular pattern — while females remain plainer.
Habitat
The form is recorded from Nkhotakota, a well-known town and harbour on the central-western shore of Lake Malawi. This stretch of shoreline includes a mix of sand and rocky habitat typical of the central lake, and Otopharynx species generally occupy the sand-rock interface or open sand rather than dense rocky reef, foraging and breeding at moderate depths. The surrounding water is warm, hard and alkaline, consistent with Lake Malawi's littoral zone throughout, though the precise depth range used by this specific form has not been documented.
Feeding
Otopharynx species span a range of feeding strategies, from open-water zooplankton feeders to more benthic invertivores picking prey from sand or rock. Which strategy applies to Otopharynx sp. "Circle" has not been documented directly, but its association with the mixed sand-and-rock habitat around Nkhotakota makes a benthic or sand-associated invertivorous diet — small crustaceans, insect larvae and other invertebrates picked from the substrate — the more likely pattern, consistent with several of the genus's sand-zone species.
Mating
Breeding behaviour has not been documented specifically for this form. By analogy with other Otopharynx and the wider Lake Malawi haplochromine assemblage, males are expected to hold a breeding territory — on rock, sand, or the interface between the two — and display their marked breeding colour to attract passing females, following the general haplochromine courtship pattern built around egg-spot markings on the male's anal fin. No locality-specific field account of courtship exists for this form.
Breeding
As in all Lake Malawi haplochromines, reproduction is by maternal mouthbrooding: the female carries the fertilised eggs and subsequent fry in her mouth, without normal feeding, for several weeks until they are ready for independent release, with the male taking no further role after spawning. Clutch size and brooding duration have not been documented for this specific form; genus-typical figures for mid-sized Otopharynx suggest a modest clutch and a brooding period of several weeks.
In the aquarium
Otopharynx sp. "Circle" is an uncommon fish in the hobby, generally reaching keepers through specialist Malawi cichlid importers rather than general retail. A tank for it should provide a sand substrate along with moderate rockwork, reflecting its likely sand-rock interface habitat, and open swimming space. Water chemistry should follow the Lake Malawi standard — hard and alkaline, pH roughly 7.7 to 8.6, temperature 75–82 °F. Otopharynx species are generally less aggressive than rock-dwelling mbuna and are usually kept successfully alongside other calm, similarly sized Malawi haplochromines. Diet should include a quality cichlid pellet supplemented with small live or frozen invertebrates such as bloodworm and brine shrimp.
Conservation
Otopharynx sp. "Circle" has not been evaluated by the IUCN and, as an undescribed form, has no Red List status of any kind. Its documented range is a single locality, Nkhotakota, on the accessible central-western shore of Lake Malawi, but no population assessment or targeted study has been published for this specific form. In the absence of that data, the honest position is that it is unassessed, and that a form known from a single locality warrants the same general caution applied to other narrow-range Malawi endemics.