Taxonomy & naming
Petrocephalus frieli was described by Sébastien Lavoué in 2012, in a paper in the Journal of Natural History covering a new species of Petrocephalus from the upper Congo River basin in Zambia. It belongs to the family Mormyridae — the elephantnoses and mormyrids — within the order Osteoglossiformes, the bonytongue fishes, one of the most ancient surviving lineages of teleosts. The holotype, CUMV 96866, is held at the Cornell University Museum of Vertebrates; the type locality is the Luapula River at Samfa Rapids, near a pontoon crossing on the Chambeshi River in Zambia (10.85°S, 31.17°E).
Lavoué separated the new species from other Petrocephalus of Central Africa by a combination of characters: a brownish body lacking the strong dark blotch below the dorsal fin seen in several relatives, 21–24 branched dorsal-fin rays, 28–30 branched anal-fin rays, more than 13 scale rows between the front of the anal-fin base and the lateral line, and three distinct electroreceptive rosettes on the head. The Catalog of Fishes lists Petrocephalus frieli as a valid species.
Morphology
Petrocephalus frieli is a small mormyrid, reaching about 3.5 in in standard length — modest even by the standards of a genus made up mostly of small, round-snouted fish. Like other Petrocephalus it lacks the elongated, trunk-like chin appendage (the schnauzenorgan) that identifies its better-known relative Gnathonemus, carrying instead the compact, blunt-headed body plan typical of the churchills.
The species is set apart from its Central African relatives by a brownish body without a strong dark blotch below the dorsal fin, by fin-ray counts (21–24 branched dorsal rays, 28–30 branched anal rays), by a comparatively high scale-row count between the anal fin and the lateral line, and by three distinct electroreceptive rosettes on the head — differences that matter mainly to a specialist working with a series of specimens rather than a mark visible at a glance. As in all mormyrids, an electric organ near the base of the tail generates a weak pulse discharge that the fish reads through electroreceptors spread across its skin; no species-specific description of the discharge waveform of P. frieli has been published.
Habitat
Petrocephalus frieli is known only from Zambia, in the upper Congo River basin. Records span the upper Luapula and Chambeshi rivers down to Lake Bangweulu, together with Lake Mweru, placing the species within the Bangweulu–Mweru ecoregion. The type locality, the Luapula River at Samfa Rapids on the Chambeshi River, sits within this same lake-and-river system on the Zambia border country.
The species is a freshwater, demersal to benthopelagic fish of tropical waters, consistent with a bottom-oriented, electric-sense-led way of life. Specific data on substrate, flow, temperature or pH across its range has not been published, so no numeric water parameters can be given with confidence for this species.
Feeding
No dietary study has been published for Petrocephalus frieli. Other members of the genus, and mormyrids generally, are benthic invertebrate feeders that use electrolocation to find insect larvae, worms and small crustaceans hidden in mud and sediment, and P. frieli can reasonably be expected to feed the same way — but that is an extrapolation from the family, not a documented fact for this species.
Mating
Nothing has been published on courtship or mate recognition in Petrocephalus frieli. Mormyrids in general are thought to use the pulse pattern of their electric organ discharge, which is often species- and sex-specific, in social and reproductive signalling, but no study has examined this behavior in P. frieli specifically.
Breeding
Breeding in Petrocephalus frieli is unrecorded. No spawning, egg-laying or parental-care observation exists for this species, in the wild or in captivity, and it should not be assumed to follow any particular pattern described for other mormyrids.
In the aquarium
Petrocephalus frieli has essentially no track record in the aquarium hobby. Described only in 2012 from a limited stretch of Zambian rivers and lakes, it is not a species known to be collected or traded. General mormyrid husbandry would still apply if a specimen were ever kept: a soft sand substrate for probing, dim lighting, ample cover such as driftwood and root tangles, and live or frozen invertebrate foods such as bloodworm and brine shrimp rather than flake or pellet food, which mormyrids frequently ignore.
Mormyrids as a group are also known for sensitivity to poor water quality and to several common aquarium medications, particularly those containing copper, so any specimen that did reach a tank would need cautious acclimation and conservative dosing. None of this reflects documented experience with P. frieli itself, only general practice for its family.
Conservation
Petrocephalus frieli has not been evaluated by the IUCN Red List. No conservation assessment, population trend, or documented threat exists for this species. Its known range is limited to a stretch of the upper Congo basin in Zambia — the Luapula and Chambeshi rivers, Lake Bangweulu and Lake Mweru — making it a candidate for future assessment rather than a species with an established conservation status.