Taxonomy & naming
Creagrutus calai was described by Richard P. Vari and Allison S. Harold in 2001 as part of a comprehensive phylogenetic revision of the Neotropical fish genera Creagrutus Günther and Piabina Reinhardt, published in the Smithsonian Contributions to Zoology (volume 613, pages 1–239). That monograph treated all cis-Andean species and placed Creagrutus within the family Characidae, order Characiformes. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) records the valid name as Creagrutus calai Vari & Harold, 2001, with the authority unparenthesised because the species was described in its current genus.
FishBase references the species under the family Stevardiidae, reflecting a post-2001 reclassification of some clade-level boundaries within Characiformes; however, the top-level family assignment used throughout this atlas follows Vari & Harold's treatment and the Characiformes checklist of Buckup and colleagues, which places Creagrutus firmly within Characidae. Regardless of the precise family boundary, the genus Creagrutus is one of the most species-rich in the order — exceeding one hundred valid species — and comprises small, often cryptically similar characids distributed across lowland and piedmont drainages of South America from Colombia south to Bolivia.
Morphology
Creagrutus calai is a small fish, reaching a maximum recorded standard length of approximately 2.5 in. Like the majority of the genus, it is a slender, laterally compressed characid with the typical Creagrutus body plan: a somewhat elongate profile, a terminal or slightly subterminal mouth, and the family's adipose fin set between the dorsal and caudal. Coloration in life is not well documented in the aquarium literature; preserved specimens of Creagrutus species typically show a silvery ground colour with a faint to moderately distinct lateral stripe, and pigmentation of the scales along the dorsum.
The original description by Vari & Harold (2001) provides detailed meristic and morphometric data distinguishing C. calai from its congeners within the cis-Andean assemblage. As with many species in the genus, field identification without microscopic examination of meristics is unreliable, and the species complex as a whole remains challenging to identify to species level in the field.
Habitat
Creagrutus calai is known from Colombia, with the type locality in the Pacific versant — specifically the San Juan River basin in the Chocó department near Istmina — and additional records from the western Meta River basin on the Andean piedmont in Meta department. These two drainage systems sit on opposite sides of the Andes, suggesting the species' distribution may be broader than the few collection records imply, or that the records reflect more than one population.
Based on what is known of Creagrutus ecology broadly and the habitat associations documented for C. calai, the species is benthopelagic and occupies fast-flowing, well-oxygenated clear-water streams typical of Andean foothill and piedmont drainages. The Rio Meta system near Villavicencio flows through lowland savanna terrain fed by Andean runoff and is characterised by warm, relatively clear water. The Chocó is one of the rainiest regions on Earth; streams there are typically soft, acidic, and cool relative to lowland Amazonian sites. Water-parameter data specific to C. calai collection sites have not been published in accessible sources.
Feeding
No diet study specific to Creagrutus calai has been published. FishBase assigns a trophic level of 2.4 to the species based on its size and the diet composition of close relatives, placing it near the base of the food web as a consumer of small invertebrates, organic detritus, and microorganisms.
Creagrutus species studied in other drainages are known to take small aquatic insects, crustaceans, and plant matter; a benthopelagic lifestyle in fast-flowing streams is consistent with foraging on drifting invertebrates and bottom-associated prey. Feeding biology for this species specifically must be considered data-sparse pending dedicated gut-content studies.
Mating
No mating observations have been published for Creagrutus calai. As a characid, it would be expected to practise egg-scattering spawning without parental care — the mode typical of the vast majority of Characiformes. In many small characids, spawning is associated with the rainy season when rising water levels and increased food availability trigger reproductive activity.
Spawning behaviour specific to Creagrutus is undescribed in the accessible literature. Like other egg-scattering characids, females likely deposit adhesive or semi-adhesive eggs among fine-leaved aquatic vegetation or over substrate, with males fertilising in immediate pursuit. No sexual dimorphism has been documented for C. calai.
Breeding
Creagrutus calai has not been bred in captivity in any documented account, and no breeding data are available in the hobbyist or scientific literature. The general biology of the genus would suggest a typical small-characid reproductive strategy: egg-scattering over vegetation or substrate, with no parental care and eggs developing independently after fertilisation.
Incubation period, clutch size, and fry development are all unknown for this species. Given that it has not entered the aquarium trade and no captive populations are recorded, empirical breeding data are unlikely to emerge in the near term. Any aquarist working with wild-collected specimens would be working in essentially uncharted territory for this species.
In the aquarium
Creagrutus calai does not appear in the aquarium hobby literature and is not available in the ornamental trade. It has been collected only from wild localities in Colombia and has not been maintained in captivity in any documented setting. No husbandry data — tank size, water chemistry, diet in captivity, compatibility, or behaviour — are available.
By inference from the ecology of the species (fast-flowing, clear piedmont streams, benthopelagic habits) and from what is known of Creagrutus generally, a specimen kept in captivity would likely require well-oxygenated, moderate-flow water, modest temperatures appropriate to Andean foothill streams, and a diet of small live or frozen invertebrates. These are extrapolations, not documented observations, and prospective keepers should treat them accordingly.
Conservation
Creagrutus calai was assessed as Least Concern (LC) on the IUCN Red List on 9 October 2020. The assessment reflects the absence of evidence for major population decline, range restriction, or specific threats sufficient to trigger a higher threat category, rather than positive evidence of abundance or security. As a micro-endemic species with a restricted and incompletely documented range in Colombia — known from the San Juan River basin (Chocó) and the western Meta drainage — it belongs to a category of data-sparse Neotropical species for which the LC listing is a precautionary default.
Deforestation, agricultural expansion, and artisanal gold mining are documented pressures on both the Chocó river systems and the Andean piedmont drainages of Meta department, and their effects on small, range-restricted stream fishes are poorly monitored. No targeted conservation measures for C. calai are on record. The species benefits from no collection pressure via the ornamental trade and is not a target of fisheries, but its long-term security depends on the integrity of its stream habitats in what are increasingly threatened landscapes.