Taxonomy & naming
Creagrutus ortegai was described by Richard P. Vari and Alain S. Harold in their 2001 revision of the genus Creagrutus, a major revisionary work that brought order to one of South America's more taxonomically complex characid groups. The type locality is within the Huallaga River basin of Peru. Eschmeyer's Catalog of Fishes records the valid name as Creagrutus ortegai Vari & Harold, 2001.
Creagrutus belongs to the family Characidae, the largest family of freshwater fishes in the Western Hemisphere. The genus is defined by a suite of osteological and meristic characters rather than by any single obvious external feature; species identification within the group typically requires examination of scale counts, lateral-line pore series, and gill-raker numbers. FishBase places C. ortegai under the subfamily context that some earlier classifications rendered as Stevardiinae, though Catalog of Fishes treats Characidae broadly as the governing family name.
The specific epithet ortegai is a patronym in the genitive singular, honouring Dr Hernán Ortega Torres, an ichthyologist at the National University of San Marcos in Lima whose decades of fieldwork have enormously expanded knowledge of Peruvian freshwater fish diversity.
Morphology
Creagrutus ortegai is a slender, laterally compressed characid reaching a maximum recorded standard length of 3 in, with most individuals in the 2.5–3 in range. Like other Creagrutus, it has a moderately elongated body, a small terminal mouth, and the adipose fin typical of the order Characiformes.
The overall coloration is silvery-argent, with a dark lateral stripe running along the mid-body flank. The pattern is described as tricolore — a silver ground, a black or dark stripe element, and lighter areas above and below — giving it a crisp appearance common to fast-water stream characins. Fins are generally clear to lightly pigmented. Sexual dimorphism is subtle: both sexes share the same pattern, but females develop a noticeably more rounded abdomen when in breeding condition, a reliable though not absolute field character.
Habitat
Creagrutus ortegai is known from the Huallaga River basin and the headwaters of the Aguaytia River in Peru, both of which drain the eastern slopes of the Andes into the upper Amazon system. These are montane and sub-montane drainages where streams run fast and cold relative to Amazonian lowland waters, tumbling over rocky and sandy substrates.
The species favours well-oxygenated water with strong current, including rapids and swift runs near waterfalls. Substrate in such habitats typically consists of sand, gravel, pebbles, and rock, with organic humus accumulating in slower side channels and behind boulders. Water temperatures in the Andean foothills fall in the range of roughly 70–79 °F; pH is near neutral, around 6.5–7.0, reflecting the mineral composition of the catchment. These conditions — cool, fast, clean, and moderately soft-to-neutral — are characteristic of stream-adapted Creagrutus across the genus range.
Feeding
FishBase records a trophic level of 2.3 (±0.1) for Creagrutus ortegai, placing it near the base of aquatic food webs as a consumer of small invertebrates and organic material rather than as a predator of other vertebrates. The diet in the wild likely consists of small aquatic insects and their larvae, microcrustaceans, and other benthic or drifting invertebrates typical of fast-water streams, supplemented by terrestrial insects falling to the surface.
In an aquarium context, this dietary profile translates to an uncomplicated feeder that accepts a wide range of small prepared and live foods. Good-quality small flake, micro-pellets, and frozen foods such as Daphnia, brine shrimp nauplii, and bloodworm all suit the species well. Offering a varied diet maintains condition and coloration.
Mating
Creagrutus ortegai has not been the subject of dedicated reproductive studies, but the broader biology of the genus and the information available for this species points to a pattern typical of many small stream characins: open-water egg scattering with no parental care. In the wild, spawning likely occurs over sandy or gravelly substrates or among fine-leaved aquatic vegetation, triggered by seasonal water-level and temperature cues associated with Andean rainfall patterns.
The species is gregarious and shoaling — sources recommend groups of at least ten individuals — and social cohesion is likely important in bringing fish into reproductive condition. Females are distinguished by a more rounded abdomen during the breeding period, suggesting that males and females in a group will interact and pair off when conditions are suitable. As with most characids of this ecological type, courtship displays are brief and fish scatter eggs with minimal ceremony before returning to the school.
Breeding
Specific aquarium breeding accounts for Creagrutus ortegai are sparse, and the species is uncommon in the hobby outside specialist circles. Based on genus-level biology and the general characid pattern, it is expected to be an egg-scattering, open-water spawner that deposits small, slightly adhesive eggs among fine-leaved plants or over the substrate, with no parental care provided by either sex.
Conditioned adults in a species tank with fine-leaved plants, a sandy base, and good water movement are the likely starting point for any breeding attempt. Lowering the temperature slightly or simulating a small water-level change may help trigger spawning, mimicking Andean seasonal cues. Eggs and fry would need to be separated from adults immediately to prevent predation. First foods for the fry would follow the standard small-characin protocol: infusoria or commercial liquid fry food, progressing to freshly hatched brine shrimp nauplii as the fry grow. Incubation and larval details remain undocumented in published sources.
In the aquarium
Creagrutus ortegai is a specialist's fish rather than a mainstream aquarium species, though its modest size, peaceful disposition, and preference for cool, well-oxygenated water make it an interesting subject for Andean biotope or foothill-stream community tanks. It is described as diurnal and gregarious, and should be kept in groups of at least ten individuals to express natural shoaling behaviour and to reduce stress.
The species' habitat requirements — strong current, high oxygenation, clean water, and temperatures in the 70–79 °F range — are important to replicate. A well-filtered tank with powerheads or spray bars to create surface agitation and current suits it well; stagnant or warm water is likely to cause stress and suppress immune function. Water chemistry near neutral (pH 6.5–7.0) over sand and gravel substrate with some smooth rocks will create a natural-feeling environment. Suitable tankmates are other cool-water, peaceful stream-dwellers of similar size. The species is peaceful and will not harass neighbours, but its current and temperature requirements may limit compatibility with many standard tropical community fish.
Conservation
Creagrutus ortegai is assessed as Least Concern (LC) on the IUCN Red List, with the assessment completed on 22 April 2014. No active threats to the species have been documented, and its population in remote Peruvian headwater streams is considered stable at the time of assessment.
The species' distribution in the Huallaga and upper Aguaytia drainages places it in upland Andean foothill systems that have historically been less subject to intensive agricultural conversion than lowland Amazonian habitats, which partly explains the favourable conservation outlook. Nevertheless, deforestation for coca cultivation and other land-use pressures in the Peruvian montane zone have altered some foothill stream catchments, and ongoing monitoring of Creagrutus populations in the region would be prudent. The IUCN assessment predates more than a decade of land-use change in the region, and a reassessment would help clarify whether Least Concern remains appropriate.