Taxonomy & naming
Creagrutus pearsoni was described by Volker Mahnert and Jacques Géry in 1988. The type locality is the Beni River at Villa Bella, within the Amazon drainage of Bolivia. Eschmeyer's Catalog of Fishes recognises the valid name as Creagrutus pearsoni Mahnert & Géry, 1988, and the species has not been synonymised or transferred to another genus.
Creagrutus is a large Neotropical genus in the family Characidae. Its members are predominantly small, benthic to benthopelagic stream fishes of South American lowland and foothill rivers, often collected in rainforest tributaries with swift currents. The genus is taxonomically complex, with dozens of formally described species and many others awaiting description; C. pearsoni belongs to a group spanning the upper Amazon basin and its Andean foothills.
The specific epithet pearsoni is a patronym. According to ETYFish, it honours Nathan Everett Pearson (1895–1982), an American ichthyologist associated with Indiana University.
Morphology
Creagrutus pearsoni is a compact, fusiform characid with the moderately deep body and small adipose fin typical of the genus. FishBase records a maximum standard length of 1.5 in for male or unsexed specimens, placing it among the smaller Creagrutus species.
Like other members of the genus, it displays the generally silvery colouration with subtle darker markings along the flanks that characterise many small Amazonian characids. Detailed meristic data are not widely available in non-specialist literature; the original description by Mahnert and Géry provides the diagnostic characters separating it from congeners. The species is benthopelagic in habit, suggesting an association with the lower water column and substrate.
Habitat
The IUCN assessment places C. pearsoni in the Beni, Mamoré, Madeira, Madre de Dios, and Grande river basins of Bolivia, and in the Urubamba, Ucayali, and Madre de Dios basins of Peru — collectively the upper Madeira drainage and its Andean tributaries. The species occurs at elevations from approximately 919–2,953 ft above sea level, situating it in both lowland rainforest and premontane zones.
Its habitat is characterised as small rainforest streams with mud and rocky substrates, moderate to swift currents, and moderate to significant turbidity. This is typical foothill-stream habitat in southwestern Amazonia: shaded by closed-canopy forest, fed by seasonal rains, and subject to variable flow. Water chemistry in such streams tends toward soft and slightly acidic to near-neutral, though specific parameters for C. pearsoni have not been widely published.
The species is considered rare in field surveys, and its population trend is listed as unknown on the IUCN Red List.
Feeding
The IUCN assessment records the diet of Creagrutus pearsoni as detritus and insects, a combination typical of small, benthic Amazonian characids that forage along the substrate and in the drift. Detritivory and invertebrate predation are common feeding strategies in foothill-stream communities where allochthonous organic input from the surrounding rainforest forms a major energy source.
No detailed dietary studies appear to have been published for this species specifically. Its small size and benthopelagic habit suggest it feeds on fine organic particles, insect larvae, and small invertebrates encountered on and near the substrate, consistent with what is known of Creagrutus feeding ecology more broadly.
Mating
No specific observations of reproductive behaviour have been published for Creagrutus pearsoni in the primary literature available to hobbyists. Like other small Neotropical characids, it is presumed to be an egg-scattering open spawner with no parental care — the reproductive mode that characterises the vast majority of the Characidae.
Males of small Creagrutus species may show subtle secondary sexual characters, and seasonal breeding tied to Amazonian flood cycles is likely, though specific data for this species are absent from the available sources.
Breeding
Creagrutus pearsoni has not been bred in the aquarium hobby with any documented regularity, and no captive-breeding protocols have been published. As with most small wild-caught South American characids presumed to be egg-scatterers, spawning in captivity would likely involve conditioning adults on live and frozen foods, providing fine-leaved vegetation or spawning mops, and separating adults from eggs to prevent predation.
Given the rarity of the species in the hobby and the limited published data, any attempt to breed it would require direct observation and experimentation rather than a known recipe.
In the aquarium
Creagrutus pearsoni is essentially unknown in the ornamental fish trade and is not an aquarium species in any practical sense. It is occasionally collected incidentally during ichthyological surveys in Bolivia and Peru but does not appear in hobby literature or commercial import lists.
Should specimens become available, the husbandry template for small, soft-water Amazonian stream characids would apply: a well-filtered aquarium with subdued lighting, some current, and a dark substrate, kept at tropical temperatures in the low-to-mid 20s Celsius and slightly soft, near-neutral water. A small group would be preferable to a solitary individual, and peaceful tankmates of comparable size would be appropriate. Its small size (under 1.5 in) means it is vulnerable to predation by larger fish.
Conservation
Creagrutus pearsoni is assessed as Least Concern (LC) on the IUCN Red List, with the assessment published in 2016 based on an evaluation dated April 2014. The listing reflects a range that, while not enormous, spans portions of both Bolivia and Peru within the upper Madeira system, and includes habitat within two protected areas: Parque Nacional Isiboro Sécure in Bolivia and Reserva Natural Tambopata in Peru.
The IUCN notes no major threats to the species at the time of assessment. Its population trend is listed as unknown, and the species is described as rare in field collections. The intact rainforest stream habitats it occupies in both countries remain broadly functional, though long-term deforestation and agricultural expansion in the Bolivian and Peruvian Amazon represent background pressures on this and all small endemic stream fishes in the region.