Taxonomy & naming
Triportheus angulatus was described by Johann Baptist von Spix and Louis Agassiz in 1829 from material collected on Spix's Brazilian expedition, one of a run of Amazonian characins the pair described together in that period. It sits in the genus Triportheus, a group of laterally compressed, silver, surface-dwelling characins sometimes placed in their own family, Triportheidae, and sometimes treated as a subfamily within the broader Characidae depending on the classification followed; the Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the reference point for the currently accepted arrangement and for confirming the valid combination.
The genus name Triportheus is usually parsed as "three-keeled," a reference to the ridged, blade-like belly shared by the hatchetfish-like members of the group, and angulatus (Latin for "angled" or "angular") points to the sharply angled profile of that same keel and the body's overall wedge shape. Triportheus angulatus is one of several similar-looking congeners in the Amazon and Orinoco basins, and field identification within the genus can be difficult without close examination of fin-ray counts and body proportions.
Morphology
This is a laterally compressed, silvery characin with a deep, strongly keeled belly running from the throat back to the anal fin — the "three keels" the genus is named for — and unusually long, broad pectoral fins that extend well past the base of the pelvic fins. That fin architecture, shared with the true hatchetfishes of the family Gasteropelecidae, lets Triportheus species skitter and glide across the surface in short bursts when startled, though they are not capable of the sustained aerial flight of a true hatchetfish. FishBase records a maximum size of 9.5 in standard length for unsexed and male fish, with common lengths closer to 5.5 in total length in males and 7 in total length in females, and a maximum recorded weight around 211 g.
Colouration is a simple, functional silver over most of the body, brightest along the flanks and fading slightly toward a darker, olive-toned back, with fins that are typically clear to lightly dusky. The overall look is a fast, open-water shoaling fish rather than an ambush predator — slim in cross-section, deep in profile, and built for quick, evasive bursts near the surface.
Habitat
Triportheus angulatus is widespread across major South American river systems, with confirmed occurrence records spanning the Amazon, Orinoco, Guiana and Paraguay drainages. It is a fish of open river channels, floodplain lakes and backwaters rather than fast rapids, typically holding station near the surface where its keeled body and long pectorals give it an escape advantage from subsurface predators.
As with many Amazonian floodplain characins, the species experiences strong seasonal hydrology across its range, moving into flooded forest and marginal vegetation during high water and concentrating in more open channels and lakes as water levels drop. The cache does not provide a narrow water-chemistry profile specific to wild populations beyond the aquarium parameters noted below, but the wide, multi-basin distribution implies tolerance of a range of conditions from blackwater to whitewater rivers.
Feeding
FishBase describes Triportheus angulatus as omnivorous, taking surface insects along with fruits, nuts and seeds that fall into the water from overhanging and flooded-forest vegetation — a diet typical of surface-oriented Amazonian characins that forage where the canopy meets the river. This is consistent with the group's general profile: many of the "minor characins" in this family are opportunistic grazers and foragers rather than specialised predators, in contrast to the genuinely predatory Brycon or Salminus elsewhere in the wider characin assemblage.
In the aquarium, SeriouslyFish describes the species as unfussy at the surface, taking commercial dry and flake foods readily alongside live and frozen insects and occasional fruit-based foods, mirroring its natural diet. Feeding at or near the surface suits its body plan and behaviour, and a varied diet reflecting its wild omnivory is the safest approach.
Mating
The cache does not document courtship behaviour for Triportheus angulatus, and no reliable account of pairing, colour change or spawning ritual for this species turned up in the available sources. FishBase notes sexual dimorphism in size — females reach a larger common length (around 7 in TL) than males (around 5.5 in TL) — which is the clearest documented sex difference, but there is no described external marker beyond that size difference, and no clear picture of courtship behaviour to report.
Breeding
SeriouslyFish states plainly that breeding has not been achieved in aquaria and remains undocumented in captivity for this species, and the cache does not offer any wild spawning account either. Rather than guess at a mode, the honest position is that Triportheus angulatus is essentially unbred and unstudied in this respect: hobbyists should not expect to reproduce it, and any claim to the contrary should be treated with scepticism until better documented.
Given the size dimorphism between the sexes (larger females, smaller males) and its position among open-water river characins, an egg-scattering strategy typical of many Characiformes would not be surprising, but this is inference rather than a documented fact, and the species should not be described as a confirmed egg-scatterer without a real source behind that claim.
In the aquarium
Triportheus angulatus is a peaceful, fast-moving shoaling fish and should always be kept in a proper group rather than alone or in a pair — SeriouslyFish recommends a minimum tank of around 30 US gal (roughly 48 x 12 x 12 inches) sized more for surface area and swimming length than for depth, matching the fish's surface-dwelling habits. Water parameters given are broad and forgiving: 72–86 °F and pH 5.0–7.5 with soft to moderately hard water (0–20 °H), well within reach of most home setups.
The single biggest practical hazard is jumping: this is an active surface fish with the same skittering reflex as its hatchetfish relatives, and an uncovered tank all but guarantees losses, so secure lid coverage is essential. At a maximum of roughly 9.5 in, it stays well within reach of a standard home aquarium — no risk of outgrowing the tank the way pacus or wolf fish do — and it makes an active, undemanding addition to a peaceful South American community provided tankmates are not fin-nippers and the group size is respected.
Conservation
Triportheus angulatus is assessed as Least Concern by the IUCN Red List, consistent with its wide distribution across the Amazon, Orinoco, Guiana and Paraguay drainages and the absence of any known major threat to the species as a whole. GBIF occurrence data confirm a broad, multi-basin South American range, and the species is also noted as a minor bait and subsistence-fishery resource in parts of that range rather than a target of concentrated commercial harvest.
As with many widespread Amazonian floodplain fish, localized pressures such as deforestation, damming and water-quality change in specific tributaries are long-term watch items for the broader ecosystem even though they do not currently threaten the species' overall conservation status.