Taxonomy & naming
Harttia fowleri was originally described by Jacques Pellegrin in 1908, in the Bulletin de la Société Zoologique de France (volume 33, number 6/7, page 126), from material collected in the Camopi River of French Guiana. The species has had an unusually mobile generic history. It was placed at various points in Oxyloricaria and then in Cteniloricaria before the Catalog of Fishes (Eschmeyer, CAS) and subsequent loricariine revisions settled it as the valid combination Harttia fowleri, with Cteniloricaria fowleri and Oxyloricaria fowleri treated as synonyms. The parenthetical authority — (Pellegrin, 1908) — reflects exactly this: the species was named in a genus other than the one it now occupies.
The shuffle was not arbitrary. Morphologically, H. fowleri is intermediate between Cteniloricaria maculata and Harttia surinamensis, which is precisely why earlier workers found it hard to place and why its eventual home in Harttia required the broader genus to be re-circumscribed. Within the family Loricariidae it belongs to the subfamily Loricariinae, the slender, depressed-bodied 'whiptail' lineage characterised by a long caudal peduncle and a ventral mouth flanked by paired barbels. In the aquarium trade the species carries the code L040.
Morphology
Harttia fowleri reaches about 8.5 in standard length, making it one of the larger species in the genus. The body follows the Loricariinae plan: strongly depressed (flattened top to bottom), tapering to a long, slender caudal peduncle, and clad in the overlapping bony scutes typical of the armoured catfishes. This dorsoventral flattening is an adaptation to life pressed against the substrate in flowing water, where a low profile reduces drag.
The mouth is ventral and disc-like, modified into a suckermouth that both anchors the fish in current and serves for grazing. Its overall form is, as noted by earlier authors, intermediate between Cteniloricaria maculata and Harttia surinamensis. Detailed coloration and meristic descriptions beyond the original account are sparse in the accessible literature; no reliable data on sexual dimorphism specific to this species has been published, though many Harttia males develop hypertrophied odontodes (bristle-like dermal teeth) on the head and pectoral fins during breeding condition.
Habitat
The species is a rheophile — a current-loving fish of the rapids. It is known from the coastal rivers of the Guianas, principally the Oyapock and Camopi systems along the French Guiana–Brazil border. In FishBase it is recorded as taken from rapids alongside Metaloricaria paucidens, placing it firmly among the fast-water specialists of the Guiana Shield.
These are clear to lightly tannin-stained waters running over rock and gravel in shallow, well-oxygenated rapids. Specific physico-chemical field measurements (temperature, pH, conductivity) for this species are not published in the accessible sources, but Guiana Shield rapids habitats are generally warm, soft, and slightly acidic to neutral. The flattened body and powerful suckermouth allow H. fowleri to hold position on rock surfaces where the current is strongest and dissolved oxygen highest.
Feeding
No detailed dietary study of Harttia fowleri has been published. As a rapids-dwelling loricariine with a ventral suckermouth, it is presumed to graze the aufwuchs — the film of algae, diatoms, biofilm, and associated micro-invertebrates — that coats rock surfaces in fast water, supplemented by fine organic detritus. This is the typical feeding mode for substrate-grazing Loricariinae and is consistent with its morphology, but it should be treated as inference rather than documented observation. There is no evidence that Harttia species are obligate wood-eaters in the manner of Panaqolus or Panaque.
Mating
Courtship and mating behaviour for Harttia fowleri have not been documented in the accessible literature. Within the genus more broadly, several Harttia species are known to be substrate egg-layers in which the male guards the clutch, and breeding males commonly develop hypertrophied odontodes on the snout and pectoral-fin rays. Whether H. fowleri follows this pattern has not been confirmed by published observation, and no aquarium breeding reports for the species were located. No data published.
Breeding
No breeding account for Harttia fowleri exists in the accessible sources, whether from the wild or in captivity. By analogy with congeners that have been bred, one would expect substrate spawning with adhesive eggs deposited on a flat rock or hard surface and guarded by the male, who fans the clutch until the fry hatch and become free-swimming. This is, however, extrapolation from related species rather than recorded fact for H. fowleri itself; the species is rare in the hobby and its reproduction remains undocumented.
In the aquarium
Harttia fowleri is seldom seen in the aquarium trade and appears only occasionally as the L040 code. As a large rapids specialist it has demanding requirements: a long tank with a strong, well-oxygenated current, a substrate of smooth rocks and gravel, and pristine water with zero ammonia and nitrite. Loricariines of this type are intolerant of warm, stagnant, oxygen-poor conditions, so high flow and good aeration are essential rather than optional.
Given its adult size of over 8.5 in and its need for swimming and grazing space across open rockwork, a spacious aquarium is required. Soft, slightly acidic to neutral water at tropical temperatures is appropriate based on its Guiana Shield origins, though exact maintenance parameters for this species are not documented. It should be regarded as a fish for the experienced keeper able to replicate a fast-flowing river rather than a general community subject, and its diet should centre on a steady supply of algae-based and biofilm grazing opportunities.
Conservation
The IUCN Red List assessed Harttia fowleri as Least Concern in 2020. It is a rheophilic species of Guiana Shield rapids with no major range-wide threats identified at the time of assessment. Its distribution across the Oyapock and Camopi systems spans relatively remote coastal-river habitat that has so far escaped large-scale industrial alteration. As with other rapids specialists of the region, the principal future concern would be any hydroelectric development or gold-mining sedimentation that altered flow regimes or smothered the rocky substrates on which the species depends, but no such threat is currently documented as significant for this fish.