Taxonomy & naming
Astyanax daguae was first described by Carl H. Eigenmann in 1913, originally placed in the genus Astyanax as Astyanax daguae. The species was later transferred to Tetragonopterus, which Cuvier established in 1816 for South American characids characterised by a compressed, roughly rectangular body outline. Eschmeyer's Catalog of Fishes (Catalog of Fishes, California Academy of Sciences) recognises the valid name as Astyanax daguae (Eigenmann, 1913); the parenthetical authority reflects the genus transfer from the original description.
A genus-level revision of Tetragonopterus — covering South American species and describing several new taxa — confirmed that A. daguae belongs within the genus, though the full morphological details of that revision were not retrievable during research. The species name daguae refers to the Dagua River drainage in the Colombian department of Valle del Cauca, which is the type locality region; Córdoba, Colombia has been cited in connection with the original collection, and the drainage lies along the Pacific versant of the western Andes.
This fish was long listed as Tetragonopterus daguae; Eschmeyer's Catalog of Fishes places the species in Astyanax, and the current combination Astyanax daguae is followed here.
Morphology
Astyanax daguae is a small fish, reaching approximately 1.6 in total length. Like other members of the genus it has the laterally compressed, deep-bodied profile that the name Tetragonopterus — from the Greek for 'four-cornered' or 'square-sided' — describes: the body is noticeably rectangular or rhomboidal in outline rather than the more fusiform shape typical of many other characids.
Detailed morphological data for this species beyond size and the characteristic genus-level body form are sparse in the available literature. As a benthopelagic freshwater species it likely occupies the mid-water and near-bottom zones in its native rivers, and the body plan is consistent with this. Low fishing vulnerability scores from FishBase indicate a slow life history relative to commercially targeted species, consistent with a small, deep-bodied characid.
Habitat
Astyanax daguae is a freshwater species native to Colombia, where it is endemic. Its distribution is centred on river drainages of the Pacific slope of the Colombian Andes, associated with the Dagua River and surrounding systems in the Valle del Cauca region. These rivers drain the western Andean foothills into the Pacific lowlands, a zone of high biodiversity and significant endemism among freshwater fishes.
Water chemistry data from FishBase indicate a preference for slightly acidic to neutral freshwater: pH 6.5–7.2, temperatures 75–81 °F (75–81 °F). The benthopelagic habitat classification suggests the species uses both the water column and the near-substrate zone, likely associated with river margins, vegetation, or slower reaches. The restricted range — confined to a limited area of western Colombia — is the central ecological fact underlying its Endangered status.
Feeding
Specific feeding ecology data for Astyanax daguae are not well documented in the accessible literature. Members of the genus Tetragonopterus are generally regarded as omnivores or generalised predators on small invertebrates, which is typical for the broader Characidae. Given the small body size of A. daguae (approximately 1.6 in TL), the diet likely consists of small aquatic invertebrates, zooplankton, and possibly algae or organic detritus, as is common among small river-dwelling characids of the Andean foothills.
FishBase classifies the species as harmless to humans, consistent with the small, non-predatory guild of tetras rather than any piscivorous or scale-eating behaviour. In the aquarium, small-sized omnivore tetras of this body plan typically accept standard fine-grade prepared foods, live and frozen microfoods, and small invertebrates.
Mating
No species-specific information on the mating behaviour of Astyanax daguae is documented in the available sources. As a characid, the species is expected to be an egg-scattering, open spawner with no parental care — the reproductive mode that characterises the great majority of the family Characidae. Spawning in characids typically involves courtship chasing among males and females, culminating in paired or group spawning over vegetation, substrate, or open water.
Adhesive or semi-adhesive eggs are deposited among fine-leaved aquatic plants or onto submerged surfaces in many small characid species; in river-dwelling forms, eggs may be scattered into the current. Without specific observations for A. daguae, the general characid pattern is the most defensible baseline.
Breeding
Breeding data specific to Astyanax daguae are absent from the available literature. It has not been reported in the aquarium trade or bred in captivity in any documented accounts. Based on the standard characid reproductive plan, breeding would involve egg scattering over fine vegetation or substrate, with adhesive or slightly adhesive eggs receiving no parental care and adults posing a predation risk to their own eggs and fry.
Incubation times, clutch sizes, and fry development parameters are unknown for this species. The general approach to breeding similar small characids in captivity — conditioning with live foods, spawning over dense fine-leaved plants or synthetic mops, removing adults promptly after spawning, and raising fry on infusoria then newly hatched brine shrimp — would apply if captive stock were ever established, but this remains speculative given the species' rarity in collections.
In the aquarium
Astyanax daguae is essentially absent from the aquarium hobby. Its Endangered status, restricted range in western Colombia, and apparent absence from trade records mean that captive specimens are extremely unlikely to be encountered. There is no established husbandry literature for this species, and it should not be collected from the wild.
If captive specimens were to become available through legitimate conservation breeding, the water chemistry parameters derived from its native range — pH 6.5–7.2, temperatures 75–81 °F (75–81 °F) — would be a reasonable starting point. As a small characid endemic to Andean Pacific-slope rivers, it would likely benefit from clean, well-oxygenated water with moderate flow, a densely planted environment, and live or frozen foods to supplement the diet. Any responsible husbandry would need to be coordinated with conservation programmes given the species' threatened status.
Conservation
Astyanax daguae is assessed as Endangered (EN) on the IUCN Red List, with the assessment conducted in October 2014 under criteria B1ab(iii). These criteria indicate that the species has a restricted extent of occurrence, that its range is severely fragmented or limited to a small number of locations, and that there is a continuing decline in the quality of its habitat — specifically the area, extent, or quality of its freshwater habitat.
The species is endemic to Colombia and is confirmed on official checklists of Colombian endemic freshwater fishes. The Pacific-slope rivers of the Colombian Andes are under sustained pressure from agriculture, deforestation, water extraction, and infrastructure development in the Valle del Cauca region. For a narrow endemic with no reservoir population outside its native drainage, any sustained habitat decline translates directly into population decline. The species is not known to be held in captivity in significant numbers, which limits any ex-situ conservation buffer. Protection of the Dagua River watershed and adjacent drainages is therefore the primary lever for this species' survival.