Taxonomy & naming
Petrocephalus okavangensis was described in 2012 by Bernd Kramer, Roger Bills, Paul Skelton and Michael Wink as part of a critical revision of the genus Petrocephalus in southern and eastern Africa, published in the Journal of Natural History. That revision resurrected the species Petrocephalus tanensis and described five species new to science, of which P. okavangensis was one. The genus sits in the family Mormyridae — the elephantnoses and mormyrids — within Osteoglossiformes, the bonytongue fishes, one of the older surviving lineages of teleosts.
The holotype, SAIAB 030046, was collected from the Thoage River at Nguma (Guma) Lagoon in the Okavango system, Botswana (18°57'43.2"S, 22°22'26.1"E), which is the type locality. Forty-one paratypes are held under the register number SAIAB 186062. No synonyms have since been documented for the name.
Morphology
Petrocephalus okavangensis is a small mormyrid, reaching about 3.5 in in standard length — one of the more compact churchills described in the 2012 revision. Like other members of the genus it has a laterally compressed body, a rounded, blunt head, and a small downturned mouth rather than the elongate chin appendage seen in the related genus Gnathonemus. In the original description the species carries 20–24 dorsal fin rays and 27–32 anal fin rays, with no spines in either fin.
As in all mormyrids, an electric organ near the base of the tail generates a weak, pulse-type discharge that the fish reads through electroreceptors spread across its skin. Recordings from two female specimens found a triphasic waveform — a strong head-positive phase (P1), a head-negative main phase (N), and a weaker head-positive phase (P2) — with a mean pulse duration of about 574 microseconds (range 520–628 μs), measured at 77 °F under a 2% threshold criterion. Each species in the genus tends to carry its own discharge shape, and this is one of the few Petrocephalus species with published discharge data specific to it rather than inferred from relatives.
Habitat
Petrocephalus okavangensis is known from the Okavango River drainage between Angola and Botswana, with the type locality at Nguma (Guma) Lagoon on the Thoage River in the Okavango panhandle, Botswana. It has also been reported from the Zambezi River in Angola. FishBase classifies the species as freshwater and demersal, occupying tropical freshwater systems of southern Africa.
Specific temperature and pH figures have not been published for this species. The Okavango and upper Zambezi drainages it inhabits are seasonal floodplain rivers, but that description applies to the wider basin rather than to a measurement taken for P. okavangensis itself.
Feeding
Diet has not been documented specifically for Petrocephalus okavangensis. Other members of the genus are benthic invertebrate feeders that use electrolocation to find small prey — insect larvae, worms, and tiny crustaceans — hidden in mud and vegetation, then take them with a quick strike of the small downturned mouth. The same pattern is likely here, though it has not been confirmed for this species.
Mating
No courtship or mating behavior has been published for Petrocephalus okavangensis. Two female specimens have had their electric organ discharge measured and described, but that work addressed waveform structure rather than reproductive signalling. In mormyrids generally, the electric discharge is thought to carry information used in species and mate recognition, but nothing has been recorded to confirm that role for this species.
Breeding
Breeding in Petrocephalus okavangensis is unrecorded. No account of spawning, egg deposition, or parental care exists for this species in the wild or in captivity, and — as with most Petrocephalus described in the last two decades — it has essentially no history in the aquarium trade from which such observations might otherwise come.
In the aquarium
Petrocephalus okavangensis has no established presence in the aquarium hobby; it is known from a limited stretch of the Okavango and upper Zambezi drainages and was described too recently to have built any keeping record. General mormyrid husbandry would apply if it were ever offered: a soft sand substrate for probing, dim lighting, ample cover, and stable, clean water, since mormyrids as a group tolerate poor water quality and many medications poorly. Live or frozen invertebrate foods rather than dry foods would be the expected diet, following the pattern documented for the wider genus.
At under 4 in it would not be a large fish to house, but none of this is drawn from experience with the species itself — it should be read as general genus practice, not a track record for P. okavangensis.
Conservation
Petrocephalus okavangensis has not been evaluated by the IUCN Red List. Its known range spans the Okavango River drainage between Angola and Botswana, with an additional record from the Zambezi River in Angola. No population trend, abundance estimate, or threat data has been published for the species.