Taxonomy & naming
Pinirampus pirinampu was described by Johann Baptist von Spix and Louis Agassiz in 1829, in the monumental work on Brazilian fishes published from Spix's South American collections. The species belongs to the family Pimelodidae — the long-whiskered catfishes of South and Central America — and is placed in the monotypic genus Pinirampus, which holds only this single species. The Catalog of Fishes (Eschmeyer, CAS) treats Pinirampus pirinampu as the valid name; older literature occasionally placed it under Pimelodus or Rhamdia, but those combinations are no longer current.
Pimelodidae is a large, diverse Neotropical family that includes some of the largest freshwater catfishes in the world — the goliath catfish Brachyplatystoma filamentosum and the redtail catfish Phractocephalus hemioliopterus are relatives. Within that company, Pinirampus is distinctive for its unusually broad, flattened barbels, which give rise to the English vernacular name flat-whiskered catfish. The specific epithet pirinampu is drawn from a vernacular Amerindian name used locally along the Amazon.
Morphology
The flat-whiskered catfish is a large, elongated pimelodid with a broad, somewhat depressed head and the characteristically long maxillary barbels of its family — here notably flattened rather than rounded in cross-section, the feature that sets the genus apart. The body is cylindrical behind the head, tapering to a deeply forked caudal fin. Coloration is generally grey-brown to olive above, paler or creamy below, without strong patterning.
Maximum recorded total length is 47 in (FishBase), though most wild-caught adults run 31.5–39.5 in; sexual maturity is reached at around 17.5 in and above. Like all pimelodids, the skin is completely scaleless and naked, with no bony plates or embedded scutes. The dorsal and pectoral fins are preceded by stiff, serrated, locking spines: the serrations point backward on the dorsal spine and both forward and backward on the pectorals, and the locking mechanism means a spine caught in a net is extremely difficult to free without injury to the fish or the keeper.
Habitat
Pinirampus pirinampu ranges across the major lowland river drainages of tropical South America — the Amazon and its tributaries, the Orinoco system, the Paraná-Paraguay system, and the Essequibo drainage of Guyana. It is a benthic, river-channel species found over sand and mud substrates in large, warm rivers and flooded plains.
FishBase records field temperatures of 72–82 °F and a pH range of 6.0–8.0, reflecting its broad tolerance across the varied chemistry of Neotropical rivers — from slightly acidic blackwaters to clear, near-neutral white-water systems. It is potamodromous: like other large pimelodids, it undertakes seasonal upstream migrations linked to the flood cycle, a behaviour well known from commercial fisheries records in the Amazon basin. It does not depend on soft, acidic blackwater specifically; its native rivers span a wide chemical range.
Feeding
Pinirampus pirinampu is a piscivore and generalist carnivore. In the wild it preys on fish and any invertebrates within reach, hunting primarily at dusk and after dark from the river bottom. Its large gape and powerful build mean it is capable of taking sizeable prey.
In the aquarium and in commercial grow-out operations it accepts large meaty foods: whole or cut fish, large prawns, earthworms, and high-protein sinking pellets formulated for large predatory catfish. Any tankmate small enough to fit in its mouth is at serious risk; companions must be conspicuously larger. Live food is not required but is readily taken. Like most large pimelodids it is an opportunist — it does not need coaxing to feed, but portion size should be calibrated to avoid grossly fouling a large tank.
Mating
In the wild, Pinirampus pirinampu undertakes upstream spawning migrations during the flood season, a pattern shared by many large pimelodids across South America — the flooding of lateral channels and várzea forest floors provides both spawning triggers and nursery habitat for larvae. The exact spawning conditions (temperature drop, photoperiod, water-level change) that trigger mating are not fully documented in the literature, but the migratory, seasonally triggered pattern is well established for the family.
Sexual maturity is reached only at relatively large size — around 17.5 in and above — meaning a fish must be maintained for many years before it even approaches reproductive age. There are no confirmed records of pair bonding or territory establishment in the way seen in smaller, cave-spawning catfishes; spawning in wild pimelodids is typically a broadcast event involving upstream aggregations of fish.
Breeding
Pinirampus pirinampu is not bred in the home aquarium. Like most large pimelodids, commercial production relies on hormone-induced spawning: broodfish are injected with pituitary extract or synthetic gonadotropin-releasing hormone analogues (GnRHa) under controlled conditions on fish farms and in public aquarium programmes, a technique routinely applied to large Amazonian catfishes that will not spawn naturally in captivity.
The practical reality for the home aquarist is unambiguous: this species reaches reproductive maturity only at 45+ cm, matures over many years, and eventually grows to pond or public-aquarium scale. The prerequisite tank volume for even a juvenile approaches 1,0.5 US gal; housing a breeding pair or group of adults would require dedicated facilities far beyond a domestic aquarium. There is nothing for the hobbyist to attempt here — breeding information is relevant only to professional aquaculture and zoological institutions.
Facts.breeding.mode reflects this: commercial and institutional hormone-induced spawning only; not a home-aquarium breeding subject.
In the aquarium
Pinirampus pirinampu is unequivocally a specialist's fish, and the single most important piece of care advice is the size trap warning: juveniles offered at 2–4 in in fish shops grow into animals 31.5–47 in long that require ponds or custom-built public-display systems. A minimum tank of 250 US gal is cited for a juvenile; an adult requires substantially more. Unless that provision is genuinely in place before purchase, this species should not be bought.
Beyond size, several care points demand attention. The skin is completely scaleless and naked, making Pinirampus pirinampu significantly more sensitive to copper-based medications and many other treatments than a scaled fish — dose at half the stated rate at most and follow scaleless-fish guidance. The locking, serrated pectoral and dorsal spines tangle dangerously in a net and can inflict a serious puncture wound; always move this fish in a container, never in a net. It is territorial toward similarly sized fish, so tankmates of the same species or comparable large catfishes require careful management and a large enough space to establish distinct zones. All tankmates must be too large to swallow.
Water parameters follow the natural range: 72–82 °F, pH 6.0–8.0. High mechanical and biological filtration is essential given the volume of waste produced. The fish is primarily nocturnal and appreciates large hiding structures — sections of large-diameter pipe, overhanging rockwork — where it can rest through the day. It is recommended only for experienced keepers with the infrastructure to house it for the twenty-plus years it may live.
Conservation
The IUCN Red List assesses Pinirampus pirinampu as Least Concern, as of the December 2020 assessment. The species has a wide natural range across the Amazon, Orinoco, Paraná and Essequibo basins and supports commercial artisanal fisheries in several countries, as well as a sport-fishing following. Its broad distribution across multiple large drainages buffers it against localised threats.
That said, large-bodied pimelodids broadly face long-term pressure from habitat change — dam construction alters seasonal flood pulses on which potamodromous migration depends, and the major Amazonian rivers face increasing agricultural and industrial sedimentation. The aquarium trade draws on wild-caught juveniles, but volume is modest compared with commercial food-fish harvests. No aquarium-specific conservation concern has been flagged for this species at this time.