Taxonomy & naming
Potamorhina altamazonica was described by the American palaeontologist and naturalist Edward Drinker Cope in 1878, placing it in the family Curimatidae within the order Characiformes — the large Neotropical group that also contains the piranhas, pacus, tetras and headstanders. The genus Potamorhina currently comprises several small-mouthed, detritivorous characins distributed across the major Amazon and Orinoco drainages, and the Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the governing authority for the valid combination Potamorhina altamazonica (Cope, 1878).
Curimatids as a group are often overlooked outside fisheries and ichthyological circles because they lack the visual drama of the family's better-known relatives, but they are ecologically important detritus-processing fish in Amazonian floodplain food webs and, in several genera including Potamorhina, economically important food fish for riverine communities. The vernacular name "llambina" is used across much of the Peruvian and Colombian Amazon for this and closely related Potamorhina and Curimata species.
Morphology
Potamorhina altamazonica has the elongated, laterally compressed, silvery body typical of curimatid characins — a streamlined, fusiform shape built for maintaining position in moving river water rather than for bursts of predatory speed. FishBase records a maximum length of 10.5 in standard length, though most individuals encountered in the wild run smaller, with reports citing a typical adult size closer to 6–7 in and a maximum nearer 12 in total length.
Like other curimatids, the mouth is small, subterminal or ventrally positioned, and adapted for sifting fine organic material and sediment from the substrate rather than for seizing prey — a build that immediately signals its detritivorous habit rather than any predatory lifestyle. Colouration is unremarkable silver typical of open-water and mid-water Amazonian shoaling fish, with no reported dramatic seasonal or sexual colour change in the sources reviewed.
Habitat
The species inhabits the Amazon and Orinoco river basins across Peru, Colombia and Brazil, favouring slower-flowing lowland forest rivers and their associated floodplain habitats rather than fast, rocky headwater streams. FishBase records water temperatures of roughly 72–79 °F and a pH range of 6.0–7.5 across its range — warm, circumneutral to mildly acidic conditions consistent with Amazonian and Orinocan lowland rivers generally, without the extreme blackwater chemistry sometimes assumed for Amazon fish.
As a floodplain species, its habitat use shifts with the seasonal flood pulse: reproductive research on the Ucayali River (a major Amazon tributary in Peru) ties its spawning migration specifically to the rising-water and flood-transition phase, when newly inundated floodplain forest provides feeding and nursery habitat unavailable during low water.
Feeding
Potamorhina altamazonica is a detritivore, feeding on organic matter and microorganisms at the river bottom rather than on other fish, insects or plant matter in the way many characins do. This bottom-grazing habit is shared broadly across the curimatid family and places these fish in a similar ecological role to Prochilodus and the curimatas — processing sediment-bound detritus and biofilm into a form usable further up the food chain, including by the predatory fish and human fisheries that depend on abundant forage species like this one.
No aquarium feeding data is available in the sources reviewed, since the species has essentially no aquarium-hobby presence; any home care would need to replicate a detritivore's diet with sinking, vegetable- and microorganism-rich foods rather than the flake, pellet or live-food diets suited to predatory or omnivorous tankmates.
Mating
Potamorhina altamazonica is a migratory, seasonal spawner rather than a fish that pairs off and courts in place. Reproductive-ecology research on the Ucayali River in Peru documents a defined spawning season running from October through March, with peak spawning activity concentrated in January and February — timed to the rising-water and flood-transition period when floodplain forest habitat becomes available. Estimated sizes at first sexual maturity are reported at roughly 7.5 in for males and 7 in for females, both consistent with the species' modest maximum size.
No distinct courtship display, pairing behaviour or external sexual dimorphism is documented in the sources reviewed; as with many long-distance migratory characins, reproduction here is driven by seasonal hydrology and large-scale movement rather than territorial pair formation.
Breeding
This is a migratory broadcast spawner, not a nest-builder, mouthbrooder or substrate-guarder. Like its larger relatives Prochilodus and Semaprochilodus, Potamorhina altamazonica undertakes seasonal spawning migrations timed to the Amazonian flood pulse, with the Ucayali River population studied specifically showing an October–March spawning season peaking in January–February during the rising-water phase. Eggs and early life stages are presumed to be released into open water and dispersed with the current and floodplain inundation, in the pattern typical of migratory Neotropical characiforms, though the sources reviewed do not describe egg or larval biology in detail for this species.
There is no evidence in the sources reviewed of aquarium or hobbyist breeding of Potamorhina altamazonica, and none should be assumed — like many of the larger migratory curimatids and prochilodontids, its reproduction depends on long-distance river movement and seasonal flooding that cannot be replicated in a home aquarium. Any commercial-scale propagation, if it exists, would be a fisheries or aquaculture matter rather than a hobby one, and no such programme is documented here.
In the aquarium
Potamorhina altamazonica is not an aquarium fish in any practical sense — it does not appear in the sources reviewed as a hobby species, and its ecology argues against attempting it as one. It is a river-migratory, detritus-grazing shoaler that likely needs current, open swimming space and access to fine sediment substrate to express normal feeding behaviour, none of which are readily replicated in a display tank, and its natural life history depends on long-distance seasonal migration that a closed aquarium cannot provide.
Where this species matters is regionally, as part of the Amazonian and Orinocan subsistence and small-scale commercial fishery alongside better-known food fish such as Prochilodus and other curimatids — llambina and related Potamorhina species are caught and sold in riverine markets across Peru, Colombia and Brazil. A prospective keeper drawn to this genus or family for an aquarium is better served by smaller, well-documented hemiodontid or curimatid relatives with established hobby care information, rather than assuming this species' needs from general characin-keeping experience.
Conservation
Potamorhina altamazonica has not been formally assessed by the IUCN Red List and currently carries a status of Not Evaluated. This is a common situation for widely distributed, locally abundant Amazonian and Orinocan food fish that are ecologically well-documented through fisheries and reproductive-biology research but have not gone through a formal global conservation assessment.
Its wide range across the Amazon and Orinoco basins and its continued presence in regional fisheries suggest it is not currently a species of acute conservation concern, but as with other floodplain-migratory characins, its reproduction is tied to natural flood-pulse hydrology and open river connectivity — pressures such as damming, floodplain forest loss and overfishing that affect migratory Amazonian fish generally would be relevant long-term watch items for this species even in the absence of a formal assessment.