Taxonomy & naming
Astyanax yariguies was first described in 2012 by Torres-Mejia, Hernández, and Senechal, originally under the genus name Astyanacinus, as Astyanacinus yariguies. Subsequent review of Astyanacinus — a genus whose limits have long been uncertain relative to the sprawling Astyanax — led to the species being reassigned to Astyanax, where it currently stands. The authority is therefore written in parentheses, reflecting the change of genus from the original description.
Astyanax is one of the most species-rich genera in the family Characidae and one of the most widely distributed freshwater fish genera in the Americas, ranging from the southern United States deep into South America. The genus is notoriously difficult taxonomically: dozens of species have been described, many are known from few specimens, and the group has been subject to repeated revisions. A. yariguies falls within the South American contingent of the genus and is distinguished by characters assessed at the time of its description, though detailed published information on its morphological diagnosis remains sparse in widely available literature.
Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) is the governing authority for the valid name Astyanax yariguies.
Morphology
Published data for Astyanax yariguies are limited. FishBase records a maximum size of 3 in standard length, placing the species in the small-to-medium range for the genus. Like other members of Astyanax, it is presumed to have the typical characid body plan: moderately compressed laterally, with a well-defined adipose fin, a forked caudal fin, and the series of small teeth characteristic of the family.
No detailed published account of its colouration or meristics is available in widely accessible sources. Astyanax species from the Magdalena system and adjacent Colombian drainages often show a silvery body with a dark lateral stripe or humeral spot, but specific diagnostic characters for A. yariguies cannot be stated with confidence from the available cache. Data on this species remain sparse, and a thorough morphological description awaits broader dissemination of the original 2012 publication.
Habitat
Astyanax yariguies is known from tributaries of the Río Cascajales within the Río La Colorada basin, itself part of the larger Río Magdalena drainage system of Colombia. The Río Magdalena is the principal river of Colombia, draining the Andean highlands westward to the Caribbean, and its middle and lower reaches support an exceptionally diverse freshwater fish fauna.
No detailed microhabitat data for A. yariguies are available in current literature. Given the geography of the Río Cascajales watershed — foothill and lowland tributaries flowing through a region that was historically forested — the species likely occupies clear to moderately turbid streams with moderate current, though this is inferred from regional context rather than published field records. Specific water-chemistry data (pH, temperature, hardness) for its collection sites have not been documented in accessible sources.
Feeding
No published dietary study for Astyanax yariguies is known. Members of the genus Astyanax are broadly omnivorous, consuming invertebrates, plant material, and small fishes depending on body size and local food availability. Species from Colombian Magdalena tributaries of comparable size typically feed on aquatic invertebrates, fallen terrestrial insects, algae, and plant detritus.
In the aquarium, Astyanax species of similar size generally accept a wide range of prepared foods — flake, small pellets, and granules — along with frozen and live invertebrates such as Daphnia, brine shrimp, and bloodworm. A varied diet is appropriate, though formal aquarium-keeping data specific to A. yariguies are not available.
Mating
No published mating observations specific to Astyanax yariguies exist in the available literature. Members of Astyanax are egg-scattering, open-water or plant-associated spawners with no parental care, a pattern consistent across the genus and the broader characid family. Males and females in breeding condition typically scatter adhesive or semi-adhesive eggs among fine-leaved aquatic vegetation or over the substrate, with spawning triggered by rain events or rising water levels in the wild.
Sexual dimorphism in Astyanax species of this size class often involves females becoming noticeably fuller in the abdomen when gravid, while males may be slightly slimmer. No specific courtship or pairing behaviour has been documented for this species.
Breeding
No captive breeding records for Astyanax yariguies are known from available sources. By analogy with other small Astyanax, breeding in captivity would likely follow the egg-scattering pattern typical of the genus: a group of conditioned adults spawning over fine-leaved plants or a spawning mop, depositing adhesive eggs that the adults would subsequently eat if given access. Removal of eggs or adults after spawning and rearing fry separately on infusoria followed by small live foods would be the standard approach.
Given the species' limited distribution and the lack of documented importation into the hobby, captive specimens are almost certainly absent from the aquarium trade at present. Breeding data specific to A. yariguies remain to be established.
In the aquarium
Astyanax yariguies is not known to be available in the ornamental fish trade. No aquarium-keeping records or care guides specific to this species have been published. As a small Astyanax from a Colombian foothill river, it would likely be kept similarly to other tetras of comparable size: a well-filtered aquarium of moderate length, soft to moderately hard water in the tropical range, kept in a school of six or more individuals, and offered a varied diet of prepared and live or frozen foods.
Any aquarist who encounters this species should note its Data Deficient IUCN status and restricted range, and consider that wild-caught specimens would represent a scientifically significant collection. The species is included here for completeness of the Colombian and Magdalena fauna covered by this atlas; practical hobby data are absent.
Conservation
The conservation status of Astyanax yariguies has not been formally assessed by the IUCN; FishBase lists the species as Data Deficient (DD), meaning insufficient data exist to determine its risk category. Its known range is restricted to tributaries of the Río Cascajales in the Río Magdalena system of Colombia — a narrow distribution that, if accurate, would make it potentially vulnerable to habitat degradation in the Magdalena basin.
The Río Magdalena catchment faces substantial anthropogenic pressure: deforestation, agricultural runoff, mining, and dam development have degraded water quality and altered hydrology across much of the basin. How A. yariguies responds to these pressures, and whether its range extends beyond the Río Cascajales tributaries, remains unknown. A formal population survey and IUCN assessment would be valuable. The species' common name honours the Yariguíes people, who inhabited the Río Cascajales watershed and defended it against colonial incursion for roughly 400 years; the Yariguíes were subjected to violent campaigns of extermination in the mid-twentieth century. Naming the fish after them is an act of commemoration as much as geography.