Taxonomy & naming
Spatuloricaria atratoensis was formally described by Leonard Peter Schultz in 1944 in Copeia (number 3, page 155), based on specimens from Río Truando, a tributary of the Río Atrato, Colombia. No synonyms are recorded; the name has remained stable since the original description, and the Catalog of Fishes (Eschmeyer, CAS) recognises Spatuloricaria atratoensis Schultz, 1944 as the valid combination.
The genus Spatuloricaria belongs to the subfamily Loricariinae — the whiptail catfishes — a diverse group united by the strongly depressed body, the ventrally placed sucking mouth, and the loss of the adipose fin. The genus name joins Latin spatula (flat-bladed implement) with Latin lorica (body armour), pointing both to body shape and to the family's characteristic bony scute covering. The species epithet atratoensis is a toponym derived from the Río Atrato, the Colombian river in whose tributary system the type specimens were collected.
Morphology
Adults reach 13.5 in standard length (SL). The body follows the Spatuloricaria ground plan: extremely depressed and elongate, covered in bony scutes, with a projecting spatulate snout overhanging the fully ventral mouth. The overall silhouette in life is ribbon-like, allowing the fish to lie flush against the substrate.
As in other members of the genus, S. atratoensis exhibits clear sexual dimorphism in adults. Viewed from above, the male head forms an isosceles triangle — narrower and longer in the rostral axis — while the female head is more equilateral in outline. Males also develop more pronounced odontodal growth on the cheeks (interopercular odontodes) and possess pectoral fin spines that are shorter and thicker than those of females. These dimorphic characters are shared with congeners including S. curvispina and allow reliable sex determination in mature individuals.
Habitat
Spatuloricaria atratoensis is confined to the Atrato River drainage in north-western Colombia. The Río Atrato is a notable system: it drains one of the wettest regions on Earth (the Chocó bioregion), flows northward through lowland rainforest, and empties into the Gulf of Urabá on the Caribbean coast — making it hydrologically distinct from the Magdalena, despite their geographic proximity. The Atrato is characterised by high discharge, heavy rainfall year-round, and dark, tannin-stained water in its forested headwaters.
The type locality, Río Truando, is a western tributary of the Atrato flowing through Chocó-type lowland rainforest. No water chemistry measurements specific to this species are available in the published literature. Loricariine whiptails in comparable Chocoan drainages typically inhabit sandy and gravel river beds in slow to moderate current, pressing themselves flat against the substrate. Given the Chocó's soft, acidic runoff from heavily forested catchments, water in the Río Truando likely tends toward low conductivity and mildly acidic pH, though this is inferred from regional hydrology rather than species-specific records.
Feeding
No feeding studies specific to S. atratoensis exist. On the basis of its family position within Loricariinae, its ventrally directed oral disc, and the modest trophic level recorded for congeners on FishBase, the species is presumed to be a detritivore and aufwuchs grazer — rasping biofilm, fine algae, and organic detritus from sand, gravel, and hard substrates with its specialised, ventrally placed teeth.
In the aquarium, the dietary approach appropriate for large whiptail loricariids generally applies: sinking algae wafers, spirulina-based pellets, and blanched vegetables (courgette, spinach, cucumber). The fish should be given opportunity to forage across a fine sandy substrate, which is the natural feeding platform for this group.
Mating
No breeding observations for S. atratoensis have been reported in aquarium literature or field studies. The species' pronounced sexual dimorphism — particularly the divergent head shapes and the odontodal elaboration in males — is consistent with male–male competition for females or territory during the breeding season, mirroring the reproductive ecology inferred for congeners.
Beyond these morphological inferences drawn from shared genus-level characters, the mating behaviour of S. atratoensis remains entirely undocumented.
Breeding
No captive breeding of Spatuloricaria atratoensis has been recorded in the hobbyist or scientific literature. The species is rarely if ever encountered in the ornamental trade, and its large adult size (nearly 13.5 in SL) would in any case demand a substantial aquarium for any breeding attempt to be feasible.
Based on the general biology of Loricariinae, egg deposition on firm surfaces with some degree of parental guarding is plausible, but this has not been documented for this species. Observations from anyone holding adult pairs would represent a genuine contribution to knowledge.
In the aquarium
Spatuloricaria atratoensis is effectively absent from the ornamental trade. It has no registered L-number, no widely used common name, and appears on no commonly maintained fish list. Any specimens that reach aquarists would be exceptional wild-caught individuals and should be treated accordingly — with careful attention to quarantine, appropriate tank sizing, and water conditions reflecting the soft, warm, likely acidic waters of its Chocó origin.
At 13.5 in SL, this is a large loricariid requiring a tank footprint of at least 150 × 19.5 in, ideally larger, with a fine sandy substrate, strong filtration, and good water movement. Temperature in the range of 75–82 °F and soft to moderately hard, near-neutral to mildly acidic water would be appropriate based on regional hydrology. The fish should be offered ample open sandy floor space for foraging alongside a few flat rocks or pieces of driftwood as resting stations.
Conservation
The IUCN Red List assessed Spatuloricaria atratoensis as Data Deficient (DD) in 2014. This classification reflects the near-complete absence of population data, trend information, or precise range estimates for the species — not a determination that it is secure. A Data Deficient listing is explicitly not equivalent to Least Concern; the true status could be considerably worse once targeted surveys are conducted.
The Río Atrato basin is among the most biodiverse freshwater systems in north-western South America and is simultaneously subject to severe anthropogenic pressure. Illegal gold and platinum mining — widespread throughout the Chocó — causes massive sedimentation and mercury contamination in the Atrato and its tributaries. Armed conflict in the region has historically limited scientific access, contributing to the data gap. Deforestation for agriculture and cattle ranching further degrades tributary habitats. For a substrate-specialist whiptail endemic to a geographically limited drainage, these cumulative pressures are a genuine concern even in the absence of species-specific decline data.