Taxonomy & naming
Petrocephalus sauvagii was described by the Belgian-born ichthyologist George Albert Boulenger in 1887 as Mormyrus sauvagii, and was later transferred to the genus Petrocephalus as the taxonomy of the family was reworked. It belongs to Mormyridae, the elephantnoses and mormyrids, within Osteoglossiformes, the ancient order of bonytongue fishes. ITIS carries the species under taxonomic serial number 649971, and current name authorities list Petrocephalus sauvagii as the valid combination. Type locality details from the 1887 description are not documented in the sources available for this account.
Petrocephalus is a large genus of small, round-headed African mormyrids that has been repeatedly revised as researchers pair morphology with the electric organ discharge each species produces. A 2008 study of the Petrocephalus fauna of Odzala National Park in the Republic of the Congo, based on specimens from the Lekoli River in the Congo basin, described five new species from the genus and helped clarify boundaries among several previously confused forms — a sign that Petrocephalus taxonomy in this part of Africa is still an active area of study rather than a settled catalog.
Morphology
Petrocephalus sauvagii is a modestly sized mormyrid. FishBase lists a maximum total length near 7 in, though most individuals recorded in the field are smaller — a survey of the Odzala population in the Republic of the Congo found specimens up to about 7.5 in standard length, and the original 1887 type specimen measured 6 in standard length. The body is ovoid, longer than it is deep, and laterally compressed, the general silhouette shared across the genus.
The mouth is unusually wide for a Petrocephalus — FishBase gives a mouth width of 2.7 to 3.7 times in head length — and sits in a subterminal position on the underside of the snout. The jaws carry 17 to 30 teeth in the upper row and 29 to 35 in the lower, and the dorsal fin carries at least 25 branched rays against at least 32 in the anal fin. As in every mormyrid, a weak electric organ near the base of the tail generates a species-specific pulse discharge read through electroreceptors spread across the skin; no electric organ discharge data specific to Petrocephalus sauvagii have been published, though that signal is the standard tool modern revisions use to separate similar-looking Petrocephalus species from one another.
Habitat
Petrocephalus sauvagii occurs in freshwater habitats across two separate river systems in tropical Africa: the Congo basin, where it has been recorded along the Lekoli River within Odzala National Park in the Republic of the Congo, and the Niger Delta in Nigeria. FishBase describes it as the only species in the genus documented from both the Congo and Niger basins, an unusually wide distribution for a genus in which most species are restricted to a single river system. Reports from coastal basins in Cameroon exist but are not well confirmed and are not treated as established here.
FishBase classifies the species as demersal, living and foraging near the bottom, consistent with the electrolocation-based lifestyle typical of mormyrids. Specific details on the rivers it inhabits — flow regime, substrate, water temperature or pH — are not documented in the sources available for this account.
Feeding
FishBase assigns Petrocephalus sauvagii an estimated trophic level of 3.3, consistent with a diet of small benthic invertebrates rather than plant matter or larger prey — the pattern typical of mormyrids generally, which locate insect larvae, worms, and small crustaceans hidden in mud and sediment using their electric sense before taking them with a quick strike. No stomach-content analysis or list of specific prey items for this species has been published.
Mating
No courtship or mate-selection behavior has been documented specifically for Petrocephalus sauvagii. In mormyrids generally, the electric organ discharge is thought to carry information relevant to species and sex recognition and to figure in courtship, but nothing in the published record ties that general pattern to this species in particular, and it should not be assumed to apply without direct study.
Breeding
Breeding has not been recorded for Petrocephalus sauvagii, in the wild or in captivity. No spawning behavior, egg description, or account of offspring has been published for this species, and as with most Petrocephalus it is not known to have been bred by aquarists.
In the aquarium
Petrocephalus sauvagii is essentially absent from the aquarium trade, and no husbandry account specific to this species has been published. What guidance exists comes from general mormyrid care rather than any track record with this fish: a soft, sand-based substrate for probing, dim lighting, ample cover such as driftwood and broad-leafed plants, and clean, stable water, since mormyrids as a group tolerate poor water quality and many common medications poorly.
Anyone attempting to keep this species would be working without a maintained-in-captivity precedent, and identification itself is a hazard — Petrocephalus species are frequently confused with one another in the trade, and reliable separation usually depends on the electric organ discharge rather than external appearance, which a hobbyist has no way to check. Feeding live or frozen invertebrate foods such as bloodworm, offered in low light, follows the general pattern documented for the genus.
Conservation
The IUCN Red List assesses Petrocephalus sauvagii as Least Concern, per the 2020 Red List update. No species-specific threats are detailed in the assessment summary available for this account, and the species' occurrence across two separate river basins — the Congo system and the Niger Delta — suggests a distribution broad enough that localized pressures in either basin are unlikely to threaten the species as a whole. As with other West and Central African freshwater fish, habitat degradation and water pollution in heavily used systems such as the Niger Delta remain long-term concerns worth watching rather than a sign of current decline.