Taxonomy & naming
Ichthyoelephas longirostris was described by the Austrian ichthyologist Franz Steindachner in 1879. It belongs to the family Prochilodontidae — the flannelmouth or detritivorous characins, close relatives of the migratory Prochilodus and Semaprochilodus food fishes — within the order Characiformes. The genus Ichthyoelephas is small, and the Catalog of Fishes (Eschmeyer, California Academy of Sciences) recognises it as distinct from Prochilodus on details of head and lip shape.
Type material was collected from the Río Cauca, Colombia, and is held at the Naturhistorisches Museum Wien in Vienna. The genus name is a Greek-derived coinage — ichthys (fish) plus elephas (elephant) — an allusion to the long, trunk-like protrusion of the snout and lips, and it is this same feature that gives the species its hobby name, "freshwater dolphin fish." The species epithet longirostris, Latin for "long-beaked," describes the same elongated rostrum.
Morphology
The defining feature of Ichthyoelephas longirostris is its head: an elongated, downturned snout ending in thick, fleshy, protrusible lips adapted for rasping algae and organic film from hard substrates, giving the fish a superficially trunk- or beak-like profile that is unlike almost anything else in the aquarium trade. The body is elongated and moderately compressed, built for holding station and grazing in the turbulent, well-oxygenated water it favours rather than for the deep-bodied, disc-like shape of a silver dollar or the blunt, big-jawed head of a piranha.
FishBase records a maximum published length of 31.5 in total length, making this one of the larger characins covered under the "Hemiodus & minor characins" umbrella — a size class much closer to a large Prochilodus or a pacu than to the modest hemiodus shoalers it is grouped with here. Colour in life is generally a subdued silvery-grey to olive, consistent with a fish that spends its time grazing rock surfaces in clear, fast water rather than displaying.
Habitat
Ichthyoelephas longirostris is endemic to the Cauca-Magdalena river system of Colombia, a basin entirely separate from the Amazon or Orinoco drainages that hold most Neotropical characins. Within that system it favours turbulent, clear stretches of river over still or heavily silted water, consistent with its rock-grazing feeding habit — the fleshy lips need clean, algae-and-biofilm-covered hard substrate to work, not soft mud or open floodplain.
The IUCN assessment describes it as a short-distance migratory species, moving within the river system rather than undertaking the long floodplain migrations of its Prochilodus relatives. The cache does not provide specific temperature or pH figures for the species; as a Cauca-Magdalena endemic it experiences the warm, seasonally variable conditions typical of Colombian Andean-foothill rivers, but precise water chemistry data is sparse and should not be assumed from Amazonian norms.
Feeding
Ichthyoelephas longirostris is a detritivore-grazer, not a predator or omnivore in the piranha or pacu sense. FishBase describes it feeding on algae and detritus scraped from rocks using its fleshy, protrusible lips, a specialisation shared with its Prochilodontidae relatives and reflected directly in the shape of its head. This places it with the quiet, substrate-grazing characins of this group rather than with the fruit-and-seed omnivores or the predatory Brycon and Salminus.
No aquarium feeding regime is documented in the available sources; a captive diet would need to replicate this grazing habit with algae wafers, blanched vegetables and biofilm-rich surfaces rather than the meaty or pelleted carnivore diets suited to predatory characins, but this is inference from its wild ecology rather than a documented hobby practice — data is sparse.
Mating
No courtship or spawning behaviour for Ichthyoelephas longirostris is documented in the available sources. The IUCN assessment notes it as a short-distance migratory species, which in Prochilodontidae relatives is typically tied to seasonal spawning movements within the river system, but no details specific to this species' pairing, timing or spawning triggers are available. Data is sparse and nothing here should be inferred beyond what the sources state.
Breeding
Breeding biology for Ichthyoelephas longirostris is not documented in the available sources, and the species is not established in aquarium or commercial aquaculture in the way its migratory Prochilodus and Semaprochilodus relatives are. Given its short-distance migratory habit noted by the IUCN, a river-spawning mode broadly consistent with other Prochilodontidae is plausible, but this is not confirmed for this species specifically, and no captive breeding — hobbyist or commercial — is documented. It should be treated as essentially unbred in the aquarium hobby.
In the aquarium
Ichthyoelephas longirostris is rare in the aquarium trade, and published husbandry information is sparse — this is a genuine data gap, not an oversight. What is certain is the size: a published maximum of 31.5 in total length makes this a large-aquarium or pond-only fish as an adult, well beyond what a typical home tank can accommodate long-term, and prospective keepers should plan for that scale from the outset or not acquire the species at all.
Its specialised rock-grazing feeding habit means it likely needs strong water flow, high oxygenation and algae- or biofilm-covered hard surfaces to express natural feeding behaviour, more akin to a large plecostomus or a Garra than to a typical open-water characin. As a threatened Colombian endemic supporting local subsistence and commercial fisheries, any specimens reaching the trade should be scrutinised for legal, sustainably sourced origin rather than wild collection from an already-pressured population.
Conservation
Ichthyoelephas longirostris is assessed as Vulnerable by the IUCN Red List (2022 assessment). It is endemic to Colombia's Cauca-Magdalena basin, and the assessment cites mining, deforestation, organic and inorganic pollution, and high fishing pressure in the upper Cauca River basin as the principal threats — a combination of habitat degradation and direct extraction rather than any single cause.
FishBase notes the species carries real importance in commercial and subsistence fisheries in Colombia, which places it in the same bind as several other large Prochilodontidae food fishes: the same qualities that make it locally valuable as a fishery resource also drive the fishing pressure contributing to its decline. As a single-basin endemic with no other populations to buffer losses, continued pressure on the Cauca River system is a direct threat to the species' long-term status.