Taxonomy & naming
Mormyrus ovis was described by the Belgian-British ichthyologist George Albert Boulenger in 1898, with a type locality above the Lufira waterfall in the upper Lualaba (Congo) system, in the Katanga region of the present-day Democratic Republic of the Congo. It sits in genus Mormyrus, family Mormyridae, order Osteoglossiformes. Catalog of Fishes lists Mormyrus ovis as the currently accepted name.
The genus name Mormyrus derives from Greek mormyros, an old name for an unrelated marine sea bream that early taxonomists reapplied to the African elephantfishes. The species epithet ovis is Latin for "sheep"; the original description does not spell out Boulenger's reasoning, so the exact allusion — most likely something about the head or snout profile — is not documented. Mormyrus is a large genus, on the order of twenty species, most built to the same long-dorsal-fin, short-anal-fin, tubular-snout plan and best told apart by fin proportions, snout length and, most reliably, their distinct electric-organ discharge rather than by eye.
Morphology
Mormyrus ovis follows the genus-typical body plan: an elongated, laterally compressed body, a long-based dorsal fin set well back over a short anal fin, a tubular, somewhat downturned snout, and a deeply forked tail. Reported maximum size is about 11.4 in total length (FishBase), which makes it a modest member of a genus whose largest species pass 17.7 in — a fish that stays a manageable size rather than one of the mormyrid giants.
Detailed colour pattern for this species is not well documented in the accessible literature; like most Mormyrus it is presumably a plain silvery-grey to olive-brown, without the bold spotting or banding seen in some of the smaller, more decorative mormyrids. As in every member of the family, an electric organ sits in the caudal peduncle just ahead of the tail, producing a weak, species-specific pulse discharge that the fish reads through electroreceptors spread across its skin — the sense it relies on to navigate and find food in dark, turbid water. Mormyrids as a group carry an unusually large cerebellum relative to body size, among the highest brain-to-body mass ratios of any fish, dedicated in large part to processing this electric sense.
Habitat
Mormyrus ovis is known from the middle and upper Congo River basin, recorded in the Democratic Republic of the Congo and the Central African Republic, with its type locality above the Lufira waterfall in the upper Lualaba system. It is a demersal, tropical-freshwater fish, living over the bottom of river channels and associated waters within that basin rather than in open water.
Congo basin rivers run warm, generally soft and slightly acidic to neutral, often dim and tannin-stained by decaying vegetation and suspended sediment — the low-visibility conditions an electric sense is built to work in. Species-specific water-chemistry data for Mormyrus ovis has not been published; the range commonly used in the hobby for Congo-basin mormyrids generally, roughly 75–82 °F and pH 6.0–7.5, is the best available guide rather than a measurement taken from this species' own habitat.
Feeding
FishBase places Mormyrus ovis at a trophic level of about 3.1, consistent with a diet weighted toward small invertebrates rather than fish. Like other mormyrids it most likely forages over sediment and among cover, using its electric sense to detect buried or hidden prey that would otherwise go unseen in dark water, rather than hunting by sight.
Aquarium keeping guides for Mormyridae generally recommend a varied diet of live and frozen foods — mosquito larvae, bloodworm, white worms, Daphnia, Cyclops and Tubifex — offered after the lights are dimmed or off, since these are shy, largely nocturnal fish that are easily out-competed for food by more active tankmates in bright light.
Mating
Courtship has not been documented specifically for Mormyrus ovis. Across the family, the electric-organ discharge is thought to carry a courtship and species-recognition role, since each species' pulse pattern is distinct enough that fish can in principle use it to identify potential mates and rivals — but the behavioural detail behind that idea is generally thin, and nothing specific has been published for this species. Wild spawning in mormyrids is believed to follow seasonal rains and rising floodwaters, in step with many other African freshwater fish, rather than happening year-round.
Breeding
Mormyrus ovis is essentially unbred in the aquarium hobby, and breeding across Mormyridae generally is rarely, if ever, achieved in captivity. Wild reproductive biology is likewise poorly known: spawning is thought to be seasonal and flood-triggered, but clutch size, incubation time, and whether either parent guards the eggs have not been worked out for this species. No reliable published account of a captive spawning exists, and it should not be treated as a fish anyone can plan to breed.
In the aquarium
Mormyrus ovis wants a dimly lit aquarium with a soft substrate it can work with its snout, dense cover for a shy, largely nocturnal fish, and stable, good-quality water — general Mormyridae keeping practice, since species-specific guidance for this fish is not published. General guidance for the genus favours keeping three or more together rather than singly or in pairs, which tends to spread out aggression rather than concentrate it on one subordinate fish; a lone or paired mormyrid can be a target for its tankmate. At around 11.4 in maximum, it needs a substantial long-term tank but not the truly outsized housing that giant Mormyrus species eventually demand.
As a scaleless fish it is markedly more sensitive than scaled tankmates to poor water quality and to common medications, particularly copper and formalin — dose conservatively and lean on prevention through good husbandry rather than cure. It is a carnivore/invertivore that needs live or frozen foods rather than flake, and its reliance on electrolocation in a busy, brightly lit community tank works against it; it does best in quieter, dimmer company suited to its nocturnal habits rather than a typical mixed community.
Conservation
The IUCN Red List assesses Mormyrus ovis as Least Concern, an assessment dated 16 February 2009. FishBase records high resilience for the species, with a population doubling time under 15 months, and no evidence of a significant range-wide decline.
Its known range is confined to the middle and upper Congo basin, so its long-term outlook is tied to the health of that river system rather than to any documented species-specific threat — the general pressures of sedimentation, habitat disturbance and water-quality change that affect Congo basin fish more broadly, rather than anything singling this species out.