Taxonomy & naming
Creagrutus barrigai was described by Richard P. Vari and Adam S. Harold in 2001, placed in the neotropical characid genus Creagrutus — one of the largest and most taxonomically challenging genera in the family Characidae. Vari and Harold undertook extensive revisionary work on Creagrutus across the 1990s and 2000s, untangling a complex of small, morphologically similar species distributed from Central America to the southern Amazon. The genus currently sits within Characidae in the broad sense, and the Catalog of Fishes records the valid name as Creagrutus barrigai Vari & Harold, 2001.
Creagrutus belongs to the subfamily Stevardiinae (or is closely allied to it depending on the phylogenetic framework adopted), a large clade of characins that includes many small stream fishes of South and Central America. The genus is diagnosed principally by osteological and meristic characters rather than by colour pattern, which makes species-level identification challenging in the field and in the aquarium. Creagrutus barrigai is one of many species in the genus described from Peruvian and Ecuadorian Amazonia, a region with exceptionally high characid diversity.
Morphology
Creagrutus barrigai is a small, slender-bodied characin reaching a recorded maximum of 2 in standard length. The body plan is typical of the genus: fusiform, moderately compressed, with a somewhat pointed snout, a terminal to slightly inferior mouth, and the adipose fin characteristic of characins. The caudal fin is forked. Coloration in preserved specimens — as with most described Creagrutus — is a pale to silvery tan, often with a faint lateral stripe or midlateral band running from behind the head to the caudal peduncle, and with darkening along the dorsal surface.
Live coloration has not been described in detail in the primary literature for this species, and most accounts derive from museum material. The group as a whole shows little of the bright pigmentation associated with aquarium tetras, presenting instead the cryptic, silver-olive tones of a small stream predator. Sexual dimorphism has not been formally documented for C. barrigai; in Creagrutus generally, females tend toward slightly greater body depth when gravid, but differences are subtle.
Habitat
Creagrutus barrigai inhabits rivers and streams of the western Amazon basin, with confirmed records from northeastern Peru, northeastern Ecuador, and western Brazil. Within Ecuador, the species has been documented in the Napo River system, including the ichthyologically diverse waters of Yasuní National Park — one of the most species-rich freshwater fish assemblages on Earth, encompassing white-water, black-water, and clear-water drainages across the lowland Amazonian biome.
The genus Creagrutus as a whole favours small to medium-sized streams and river margins with clear to mixed waters, often with structural complexity provided by leaf litter, submerged wood, and riparian vegetation. Specific microhabitat data for C. barrigai are sparse in the published literature. The Napo drainage in which it occurs spans a wide altitudinal gradient from the Andean foothills into the lowland Amazon plain; records from Yasuní place the species in the lowland rainforest zone at low elevation. Water parameters for the occupied streams are not established for this species in the available sources.
Feeding
Specific dietary data for Creagrutus barrigai have not been published. Across the genus, Creagrutus species are understood to be carnivorous to omnivorous, feeding primarily on small aquatic invertebrates, zooplankton, insect larvae, and small crustaceans. The relatively small, terminal to subterminal mouth and fusiform body of these fishes are consistent with active pursuit of small, mobile prey in the water column and near the substrate.
In the aquarium — where the species is essentially unknown in the trade — the feeding behaviour of the genus suggests that small live and frozen foods (Daphnia, Cyclops, micro-worms, small bloodworm) would be accepted, along with fine-grade dry foods. As with other small characins of stream origin, overfeeding should be avoided and water quality maintained carefully.
Mating
No species-specific mating observations have been published for Creagrutus barrigai. Based on the reproductive biology of the broader Characidae and Stevardiinae, the species is presumed to be a free-spawning egg-scatterer, with males competing for or courting females without forming lasting pair bonds. There is no evidence of parental care in Creagrutus, and the group as a whole is not known for complex courtship displays.
Most small neotropical characins of comparable size and habitat scatter adhesive or semi-adhesive eggs among fine-leaved aquatic plants, submerged roots, or leaf litter, where the eggs develop without further attendance. Whether C. barrigai exhibits any habitat preferences for spawning sites in the wild remains undocumented.
Breeding
Creagrutus barrigai has not been bred in captivity under documented conditions, and no breeding accounts appear in the hobbyist or scientific literature. By analogy with other small, stream-dwelling Characidae, captive breeding would likely require soft to moderately soft, warm, well-oxygenated water with fine-leaved plants or spawning mops, a balanced or slightly male-skewed group, and conditioning on live or frozen foods.
Egg development and larval care details are unknown for this species. Given that the species is effectively absent from the aquarium trade, practical breeding information does not yet exist. Any captive attempt would represent new documentation for the genus in this region of its range.
In the aquarium
Creagrutus barrigai is not an established aquarium fish and is essentially unknown in the ornamental trade. Members of the genus Creagrutus occasionally appear in shipments of wild-caught Amazonian fishes — typically under generic labels such as 'Amazonian tetra' — but species-level identification is difficult without microscopic examination of meristic characters, and few importers or hobbyists pursue it.
Should the species become available, a species aquarium or a biotope setup reflecting the clear-water streams of the Napo drainage would be the appropriate approach: a well-filtered, moderately warm tank with tannin-stained or clear water, a dark substrate, driftwood, and fine-leaved plants or leaf litter. Given their small size and likely retiring nature, tankmates should be chosen carefully; similarly sized, peaceful small tetras or Corydoras catfish from overlapping Amazonian drainages would be contextually appropriate. Water parameter specifics for this species are not established.
Conservation
Creagrutus barrigai is assessed as Least Concern (LC) on the IUCN Red List, most recently evaluated in 2025 (assessment ID 159299661, taxon ID 49830076). The Least Concern designation reflects the species' relatively broad distribution across the western Amazon basin — spanning northeastern Peru, northeastern Ecuador, and western Brazil — and the absence of evidence for population declines of a magnitude that would trigger a threatened category under IUCN criteria.
The species' presence within Yasuní National Park in Ecuador provides a degree of habitat protection within its range, though much of its distribution lies outside formally protected areas. As with many small Amazonian stream fishes, the primary threats to species in this group are broad-scale habitat degradation through deforestation, agricultural runoff, and changes to hydrology in Andean-influenced drainages. No species-specific conservation actions are known to be in place for C. barrigai.