Taxonomy & naming
Cephalosilurus fowleri was described by the American ichthyologist John D. Haseman in 1911. It belongs to the family Pseudopimelodidae, the bumblebee and dwarf-pimelodid catfishes, a group that was carved out of the broader Pimelodidae as the long-whiskered catfish family was revised; the Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats Cephalosilurus fowleri as the currently valid combination in the genus Cephalosilurus.
The genus name Cephalosilurus combines the Greek kephale, "head", with Silurus, the classical catfish genus name, a nod to the disproportionately large, broad head that defines the genus. The species epithet fowleri honours Henry Weed Fowler, the American ichthyologist who worked extensively on South American fish collections in the early twentieth century. The genus is small, restricted to a handful of species across South American river basins.
Morphology
Cephalosilurus fowleri has the classic Cephalosilurus profile: a very broad, dorsoventrally flattened head that makes up a large fraction of the body, a wide terminal mouth built for engulfing prey, and long, prominent barbels used to detect food in low light or murky water. The body tapers from the heavy head to a more slender caudal peduncle, and like other pseudopimelodids it lacks scales entirely, its skin instead bearing the naked, often mottled and blotched pattern typical of the family.
Adults reach roughly 16 in total length, a substantial size for a catfish often mistaken for a small "dwarf pimelodid" cousin — this is not a nano species, and prospective keepers should plan around its real adult bulk rather than its appearance as a juvenile. As in nearly all catfishes, the pectoral and dorsal fins carry stiff, serrated spines that lock erect; these can snag a net and jab an unwary hand, so the fish is best moved in a container rather than netted.
Habitat
The species is endemic to the São Francisco River basin in eastern Brazil, recorded across the states of Minas Gerais, Bahia, Sergipe, Pernambuco and Alagoas as the river runs from the interior highlands to the Atlantic coast. It is a freshwater, demersal species of tropical rivers, living on or near the bottom rather than in open water.
Reported aquarium conditions reflect warm, moderately soft to neutral South American river water: temperatures around 73–81 °F and a pH of roughly 6.0–7.0. This is a warm tropical river fish, not a blackwater specialist, and its water needs sit closer to a generalist South American profile than to the very soft, tannin-stained extremes associated with some Amazonian catfishes.
Feeding
Cephalosilurus fowleri is a nocturnal predator that forages mainly after dark, using its large mouth and sensory barbels to locate and engulf prey rather than grazing or sifting. In the wild this almost certainly includes smaller fish and other prey items typical of a bottom-dwelling ambush predator in its size class.
In the aquarium it is reported to be reluctant on prepared foods at first, often preferring live fish initially, but keepers report it can be acclimated over time to earthworms, thawed smelt, prawns and mussels. Because it is predatory and grows large, tankmates should always be sized well beyond what it could swallow, and feeding is best offered after lights-out to match its nocturnal habits.
Mating
Specific courtship and spawning behaviour for Cephalosilurus fowleri has not been documented in the available literature; data on its reproductive biology, whether in the wild São Francisco basin or in captivity, is sparse. Nothing points to any unusual reproductive strategy such as brood parasitism or internal fertilisation in this genus, but details of pairing, spawning triggers and site selection remain unrecorded.
Breeding
Breeding of Cephalosilurus fowleri has not been documented in home aquaria. Like many large, predatory South American catfishes, it appears to fall outside the small set of species that spawn reliably in captivity, and no aquarium breeding reports were found in the sources consulted. Prospective keepers should not expect to breed this species and should treat any wild-collected or commercially available stock as such rather than assume captive-bred origin.
In the aquarium
This is a large, specialist predator catfish, not a community fish. Sources recommend a minimum tank size of around 120 US gal to accommodate its 16 in adult length — the size trap is real here, since a juvenile's modest appearance belies the bulk it will eventually reach. Provide robust filtration and, per hobbyist accounts, some keepers house the aquarium's equipment (heaters, pump intakes) externally or well protected, since the fish's spines and predatory temperament make internal fittings vulnerable.
Being scaleless, Cephalosilurus fowleri is more sensitive than scaled fish to copper-based medications and many standard treatments — dose conservatively, often at half strength, and treat with care. Its locking pectoral and dorsal spines can tangle in a net and jab the keeper, so move it in a container rather than netting it. It is reported to become aggressive when crowded and should only be housed with fish too large for it to eat; as a nocturnal species it also benefits from caves or dense cover to retreat into during the day.
Conservation
The IUCN Red List assesses Cephalosilurus fowleri as Least Concern, an assessment from 2022. As a São Francisco basin endemic, its conservation outlook is nonetheless tied to the health of that river system, which faces pressures from damming, water abstraction and habitat modification across its range in Minas Gerais, Bahia, Sergipe, Pernambuco and Alagoas. The Least Concern status reflects the species' currently apparent stability rather than an absence of basin-wide environmental pressure.