Taxonomy & naming
Hypostomus fonchii was described by Weber and Montoya-Burgos in 2002 in the Revue Suisse de Zoologie (volume 109, number 2, pages 355–368), with figures 2 and 3 illustrating the holotype (MHNG 2617.045). The type locality is given as the lower part near the mouth of Río Pauya, at coordinates 6°36'7.0"S, 75°56'26.3"W, in Quebrada John, Ucayali department, Peru, at an elevation of approximately 1181 ft. The species is accepted under the combination Hypostomus fonchii Weber & Montoya-Burgos, 2002 in the Catalog of Fishes (Eschmeyer, CAS), with no synonyms currently listed.
The original description places H. fonchii within the large, diverse genus Hypostomus Lacepède, 1803, subfamily Hypostominae, family Loricariidae. Subsequent records have extended the known range into the Río Mamoré basin of Bolivia, suggesting the species occupies upper Amazon drainages across parts of western South America. The authors noted a close relationship with H. hemicochliodon and other Peruvian Hypostomus, though a full species-group placement awaits broader phylogenetic treatment of the genus.
No L-number or trade code has been assigned to this species.
Morphology
Hypostomus fonchii is a small member of the genus, reaching approximately 5.5 in standard length (SL) — 6 in SL per FishBase records. The body bears the typical loricariid covering of interlocking bony scutes arranged in rows. The ventral surface is described as largely naked (unplated) in the type description, a feature shared with several Peruvian Hypostomus species and useful in distinguishing groups within the genus.
In the genus Hypostomus generally, the suckermouth is ventrally positioned and armed with numerous slender, bi- or multi-cusped teeth suited to rasping periphyton from hard substrates. Coloration in the genus is highly variable; no detailed colour description is available in the secondary sources consulted here beyond what is visible in the original description's figures.
Sexual dimorphism in Hypostomus follows the general loricariid pattern: males typically develop more pronounced odontodes (spine-like dermal denticles) on the cheeks and pectoral spines than females, and gravid females become noticeably broader-bodied when viewed dorsally. Whether these features are well-developed in H. fonchii specifically is not documented.
Habitat
The type locality — a quebrada (small stream) near the mouth of the Río Pauya in Ucayali, Peru — sits at around 1181 ft elevation in the sub-Andean foothills of western Amazonia. This zone is characterised by clear to lightly turbid streams running over rocky substrates with sand and clay benches, draining through forested slopes before joining the larger Huallaga and Marañón systems of the upper Amazon. FishBase records habitat notes of clear-water streams with rocky substrate over sand, clay, and shingle, with temperatures in the range of 77–79 °F at collection.
Subsequent records from the Río Mamoré basin of Bolivia (a distinct upper Amazon drainage farther south) indicate the species tolerates some degree of environmental variation across drainages. Like all Loricariidae, H. fonchii is likely dependent on well-oxygenated, flowing water and benthic hard substrates that support the biofilm communities on which it feeds.
Feeding
No diet data specific to H. fonchii are published. Its morphology — ventrally placed suckermouth, multi-cusped rasping teeth — is consistent with the typical Hypostomus feeding mode: scraping aufwuchs (periphyton, diatoms, filamentous algae, bacterial and fungal biofilm, and fine detritus) from rock surfaces and submerged wood. Some Hypostomus species also ingest quantities of sand during substrate feeding, which passes through the digestive tract. High rates of algal and biofilm grazing characterise the genus in well-lit, current-swept rocky habitats.
Mating
No behavioural observations exist for H. fonchii. The mating system in Hypostomus is not formally studied for this species. In the genus broadly, males are territorial around shelter sites during the breeding season and develop elaborated odontodes that appear to function in male–male competition and, potentially, in tactile courtship. The male typically selects and defends a cavity — a crevice between boulders or a hollow beneath a root mass — into which a gravid female is eventually coaxed.
Breeding
No breeding records exist for H. fonchii in captivity or the wild. The species has not been documented in aquarium collections, and no keeper or spotter reports appear in the literature or in the PlanetCatfish database. Cave-spawning with paternal guarding is the reproductive mode documented across Hypostomus and the wider Loricariidae; this can be stated as the expected pattern for the genus but not as a confirmed attribute of this species.
In the aquarium
Hypostomus fonchii has not been recorded in the ornamental trade and no aquarium husbandry data are available. At a maximum documented size of approximately 5.5–6 in SL, it would fall into a manageable size range for a mid-to-large community aquarium if it were ever collected and exported. The clear, cool-to-moderate temperature streams of the upper Amazon foothills (around 77–79 °F) suggest water chemistry preferences broadly similar to many other Andean-foothill plecos: well-oxygenated, moderately soft, neutral to slightly acidic water with good flow.
Without direct observation or keeper records, nothing more specific can be stated about its aquarium requirements.
Conservation
The IUCN Red List assessed Hypostomus fonchii as Least Concern in 2014. The range spans upper Amazon tributaries in Peru (Ucayali, Huallaga, Marañón, and Cushabatay systems) and extends to the Río Mamoré basin of Bolivia, and no major threats have been identified. Population trend is not known.
The upper Amazon foothill zone faces ongoing pressure from agricultural expansion, logging, and infrastructure development, particularly road-building into previously remote river systems. These pressures can increase sedimentation and alter the clear-water rocky stream habitats that Hypostomus species depend upon. At the time of its last IUCN assessment, H. fonchii was not considered at elevated risk, but no reassessment has been published since 2014.