Taxonomy & naming
Harttia fluminensis was described by Covain and Fisch-Muller in 2012, within a major treatment of the Harttiini of the Guianas (Covain, Fisch-Muller, Montoya-Burgos, Mol, Le Bail & Day, Cybium volume 36, number 1, pages 115–161). The Catalog of Fishes (Eschmeyer, CAS) recognises it as a valid species of Harttia (species id 72282).
The genus Harttia is a member of the subfamily Loricariinae — the slim, flattened 'whiptail' loricariids without an adipose fin. The specific epithet fluminensis derives from the Latin flumen, 'river', a reference to the species' rheophilic life in the main river channel. The original description distinguishes H. fluminensis from its congeners (other than H. tuna and H. trombetensis) by an incomplete abdominal plate cover and by a specific DNA barcode (GenBank JF292263); it is separated from H. tuna by a deeper head and from H. trombetensis by caudal-fin colour.
Morphology
Harttia fluminensis reaches about 6 in standard length, making it one of the larger species treated here. The body is elongate and depressed in the typical Loricariinae manner, with a single dorsal spine and seven soft dorsal rays, and a single anal spine with five soft anal rays.
A diagnostic feature is the incomplete abdominal cover: bony plating on the belly is restricted to the preanal and abdominal lateral plates, with a row of small platelets joining the two series rather than a continuous shield. The caudal fin bears a large dark band at its base — a marking that distinguishes the species from the closely related H. trombetensis, which instead shows a dark rounded blotch. Relative to H. tuna, H. fluminensis has a deeper head.
Habitat
Harttia fluminensis is known only from the Coppename River drainage in Suriname. It is a main-channel fish, frequenting rocky and sandy bottoms in fast-flowing water — a strongly rheophilic habitat. This preference for swift current over hard substrate is consistent with its flattened body form and is reflected in its name. No detailed water-chemistry measurements for the species are given in the sources available here, beyond its tropical, freshwater, demersal classification.
Feeding
No dedicated dietary study has been published for Harttia fluminensis in the sources available here. FishBase lists an estimated trophic level of about 2.5, indicating a low-trophic diet typical of the genus. As with other Loricariinae, it most likely grazes biofilm, algae and fine organic matter from rocks and sand in the river channel, but no direct feeding observations are documented.
Mating
No information on the courtship or mating behaviour of Harttia fluminensis has been published in the sources reviewed. Loricariinae are generally substrate spawners with male egg-guarding, but no species-specific account exists for this fish.
Breeding
No breeding has been documented for Harttia fluminensis, in the wild or in aquaria, in the sources available here. The species is not established in the hobby and no captive reproduction reports are known. While many Harttia are presumed paternal substrate spawners, applying that to H. fluminensis specifically would be speculation; no data has been published.
In the aquarium
Harttia fluminensis is essentially unknown in the aquarium trade, and no established husbandry guidance exists for it. Any care recommendations would be inferred from other large, rheophilic Harttia: a tank with strong, well-oxygenated flow, a substrate of sand and smooth rock, and clean, clear water at tropical temperatures, with enough length to accommodate a fish approaching 6 in. Because no genuine captive data is available, such guidance should be treated as provisional.
Conservation
The IUCN Red List assessed Harttia fluminensis as Least Concern (assessment dated 9 October 2020). Although the species is presently known only from the Coppename drainage, the assessment found no evidence of significant population decline warranting a threatened category. The Coppename basin lies largely within protected areas of central Suriname and remains relatively intact, which is favourable for a narrowly distributed, flow-dependent endemic; continued protection of its river habitat is nonetheless important to its long-term security.