Taxonomy & naming
Haplochromis macconneli was described by Peter Humphry Greenwood in 1974, in his monograph 'The Haplochromis species (Pisces: Cichlidae) of Lake Rudolf, East Africa' (Bulletin of the British Museum (Natural History), Zoology 27(3): 141–165). The type locality lies about 3 miles (roughly 3 mi) northwest of Central Island, Lake Rudolf (now Lake Turkana), Kenya, at 164–210 ft depth. The epithet honours Richard B. McConnell, Officer in Charge of the Fisheries Department at Lake Rudolf, for the help he gave the Lake Rudolf Research Project that produced Greenwood's revision. As with the other Turkana endemics, generic placement is unsettled: FishBase and the Catalog of Fishes treat the fish as Haplochromis macconneli, while some authorities place the lake's endemics in Thoracochromis, giving the alternative combination Thoracochromis macconneli. The two names refer to the same species; the disagreement is part of the long-standing taxonomic difficulty surrounding the genus Haplochromis sensu lato.
Morphology
Haplochromis macconneli is a small cichlid, reaching about 3 in standard length — slightly smaller than its lake-mate Haplochromis turkanae. The body is the typical laterally compressed haplochromine shape. Coloration in life is muted, as is the rule for a deep-water, low-light fish: bright display colours have little function in the dim profundal zone it inhabits, and preserved and trawled specimens show a plain silvery-grey tone rather than the vivid patterning of shallow rock-dwelling cichlids. Greenwood separated the species from its Turkana congeners on meristic and osteological grounds — counts and proportions and the configuration of the jaws and dentition — rather than on colour. Sexual dimorphism is presumed to follow the haplochromine pattern (breeding males more coloured, bearing anal-fin egg-spots; females plainer), but it is not separately detailed for this poorly observed species.
Habitat
The species is endemic to Lake Turkana and is the lake's deep-water haplochromine specialist. FishBase records it as confined to waters deeper than about 66 ft and most abundant at 164–230 ft, with the type series taken at 164–210 ft — making it the deepest-dwelling of the Turkana endemic flock. Lake Turkana is a warm, closed-basin, strongly alkaline desert lake fed mainly by the Omo River; surface waters run roughly 79–88 °F and pH around 8.5–9.2. At the depths macconneli occupies, the water is cooler, darker and more thermally stable than the surface, and in a lake this productive the deep zone can be oxygen-poor, so the species sits at the demanding profundal edge of the fauna's range. It is benthopelagic, living over and just above the deep open bottom rather than in the inshore shallows.
Feeding
There is no published gut-content study for Haplochromis macconneli; FishBase carries an estimated trophic level of about 3.3 derived from the feeding ecology of its closest relatives, which places it as a small carnivore/invertivore. In the deep open-water habitat it occupies, the likely food base is benthic and near-bottom invertebrates and zooplankton — the prey available in the profundal zone, where attached algae and the rich invertebrate communities of the littoral are absent. Its diet is therefore inferred rather than directly documented, and is best stated as a deep-water invertebrate feeder pending any dedicated study; the lake's small endemic flock partitions food and depth, and macconneli's contribution to that partitioning is to exploit the deepest, dimmest zone.
Mating
No courtship or pre-spawning behaviour has been described for Haplochromis macconneli, and its deep, dark habitat makes direct observation in the wild effectively impossible. What can be stated comes from its membership of the haplochromine mouthbrooders: in that lineage, males typically court females with visual displays and the anal-fin egg-spot 'dummy eggs', and females choose among them. How much of that visual repertoire functions in the low light of the profundal zone is an open and interesting question, but it is unstudied for this species. Its mating system is therefore presumed to be the standard haplochromine polygynous, male-display system, without specific confirmation.
Breeding
Haplochromis macconneli is a maternal mouthbrooder, in keeping with its haplochromine lineage and as recorded for the species. The female broods the fertilised eggs and the early fry in her mouth, releasing the young only once they are able to feed and shelter on their own. This yields small clutches of well-developed offspring — the haplochromine strategy of investing in survivorship over numbers. Specific data on clutch size, brooding period and fry development are not available for this deep-water endemic, which has essentially never been observed reproducing; they are expected to fall within the normal haplochromine range. The species has not been bred in captivity.
In the aquarium
Haplochromis macconneli is not an aquarium fish in any practical sense. As a deep-water Turkana endemic known almost entirely from research collections, it is not traded, not bred commercially, and there is no body of keeping experience for it. It would also be an exceptionally awkward subject for captivity: a fish adapted to the cool, dark, stable and possibly low-oxygen profundal zone of a strongly alkaline soda lake has demanding and unusual requirements that a normal aquarium does not reproduce. The only honest husbandry note is that this species has never been kept, no protocol exists, and any attempt would be experimental. Aquarists interested in a Turkana cichlid they can actually keep are far better served by the Turkana jewel cichlid (Rubricatochromis exsul), which is hardy and occasionally available in the trade.
Conservation
The IUCN Red List assesses Haplochromis macconneli as Least Concern, assessed on 31 January 2006 (assessors Odhiambo & Hanssens), reflecting its distribution within Lake Turkana and the absence of a documented species-specific threat. As a deep-water single-lake endemic, however, its fate is tied entirely to the condition of Lake Turkana. The lake depends almost wholly on inflow from the Omo River, and the large hydroelectric dams (Gibe III and successors) and irrigation schemes built on the Omo in Ethiopia have cut that inflow and are projected to lower lake level and raise salinity over the coming decades. Falling level and rising salinity, together with any change to the lake's deep-water oxygen and thermal structure, would bear most heavily on a profundal specialist like macconneli, whose habitat is the hardest to substitute. Its long-term security is therefore a function of the lake's hydrological future, not of any direct human exploitation of the fish.