Taxonomy & naming
Creagrutus peruanus was described by Franz Steindachner in 1876. Because Steindachner placed it in a genus other than Creagrutus, the authority appears in parentheses — (Steindachner, 1876) — indicating a subsequent generic transfer. The Catalog of Fishes (Eschmeyer, CAS) treats Creagrutus peruanus (Steindachner, 1876) as the valid name.
Creagrutus is a large genus of small characids sometimes placed in the subfamily Stevardiinae within Characidae, and FishBase tracks the family as Stevardiidae for this group; however, broader usage and the Catalog of Fishes continue to treat this lineage within Characidae. The genus is characterized by a benthopelagic lifestyle and relatively undifferentiated body form that makes species-level identification difficult without meristic counts and direct comparison with type specimens. A related congener, Creagrutus yanatili, was described from the same Urubamba drainage system, illustrating how the genus has diversified across Andean drainages in southeastern Peru.
Morphology
Creagrutus peruanus reaches a maximum recorded size of 3.5 in standard length. It has the typical Creagrutus body plan: a slender, moderately compressed form with a subterminal or slightly inferior mouth suited to picking food items from or near the substrate. Coloration in preserved specimens is silvery to pale yellowish with indistinct lateral pigmentation; live fish likely show more contrast, but detailed live color descriptions are sparse in the literature.
Like its congeners, it lacks the bright hues that attract hobbyist attention — Creagrutus are understated fish, their interest lying in their ecology and the complexity of the genus rather than in striking ornamentation. Sexual dimorphism is not well documented for this species specifically, though many small characids show subtle differences in body depth or fin shape between mature males and females.
Habitat
Creagrutus peruanus inhabits the Apurimac and Urubamba river basins of Peru — both major headwater systems of the Amazon, draining the eastern slopes of the Andes. It is classified as a freshwater, benthopelagic species, meaning it lives and feeds at or near the riverbed rather than in open water. The Andean foothills setting suggests fast-flowing, well-oxygenated, relatively cool water with a cobble or gravel substrate.
The Urubamba and Apurimac drainages cut through cloud-forest and montane-forest zones before descending toward the Amazon lowlands, providing a mosaic of habitats. The closely related Creagrutus yanatili, described from the Rio Urubamba drainage of southeastern Peru, occupies a similar habitat context, confirming that this stretch of Andean river supports multiple Creagrutus species living in sympatry or near-sympatry.
Feeding
FishBase records a trophic level of 2.3 for Creagrutus peruanus, placing it at the herbivore/detritivore end of the omnivore spectrum rather than as a predator of significant prey items. This is consistent with a benthopelagic lifestyle in which the fish picks organic material, algae, and small invertebrates from the substrate surface or the water column just above it.
In captivity, small characids of this lifestyle typically accept a range of fine-particle foods — finely crushed flake, small pellets, and frozen or live invertebrates such as Daphnia, micro-worms, and cyclops. No specific aquarium feeding data exist for this species, and hobbyist literature on Creagrutus husbandry in general is sparse.
Mating
No detailed behavioral observations of courtship in Creagrutus peruanus appear in the published record. Based on the biology of small, non-migratory Andean characids and the general Creagrutus body form, the species is presumed to be an open egg-scatterer with no parental care — the reproductive mode typical of most small characids without specialized breeding structures.
Congeners and close relatives generally spawn among fine-leaved vegetation or over gravelly substrates, with females broadcasting adhesive or semi-adhesive eggs that settle without any guarding by either parent. Reproductive seasonality in Andean foothills streams is likely tied to rainfall and runoff cycles rather than photoperiod alone.
Breeding
Captive breeding of Creagrutus peruanus has not been documented in the hobbyist or scientific literature available for this article. By analogy with other small open-spawning characids, breeding would likely require soft, slightly acidic to neutral water, a temperature in the mid-20s Celsius, and fine-leaved plants or spawning mops as egg-deposition sites. Eggs would be expected to be small, adhesive, and unattended by either parent, with adults liable to eat any eggs they encounter.
Given the species' rarity in the trade, aquarium observations and breeding accounts — should they exist — would constitute a meaningful contribution to knowledge of the genus. Hobbyists who obtain specimens from specialist importers should document behavior and water parameters carefully.
In the aquarium
Creagrutus peruanus is a rare import that seldom appears in the trade outside of specialist shipments targeting Peruvian fauna. Aquarists interested in the species would source it through importers dealing in wild-caught Peruvian characids, where it might appear as a bycatch item alongside more sought-after species from the same river systems.
Care requirements are inferred from habitat data and the biology of similar Andean small characids: clean, well-oxygenated water with moderate to brisk flow, temperatures in the low-to-mid 20s Celsius, and a natural-style aquascape with fine substrate and shaded areas would replicate the mountain-foothill stream environment. The species' benthopelagic habit means some competition for bottom space should be anticipated if kept with other substrate-oriented fish. Its small size and modest temperament suggest compatibility with other peaceful, similarly sized species.
Conservation
The IUCN Red List assessed Creagrutus peruanus as Least Concern (LC) on 22 April 2014. The species has a restricted but apparently stable range within the Apurimac and Urubamba river systems of Peru, and there is no evidence of a rapid population decline meeting threshold criteria for a threatened category. Key Biodiversity Area assessments have also recorded the species as LC (2024), consistent with the IUCN position.
That said, a species confined to Andean headwater drainages is inherently exposed to threats from deforestation in cloud-forest catchments, mining activity, agricultural runoff, and the downstream effects of dam construction. Monitoring in high-Andean river systems lags behind that in lowland Amazonian habitats, so population trends for range-restricted species such as Creagrutus peruanus are poorly tracked. The Least Concern listing reflects the current absence of evidence of decline rather than a deep evidence base confirming population health.