Taxonomy & naming
Sternarchorhynchus montanus was described by de Santana & Vari in 2010 as part of a broad taxonomic revision of the genus Sternarchorhynchus, within the family Apteronotidae — the ghost knifefishes — in the order Gymnotiformes, the New-World electric knifefishes. Gymnotiformes are bony fish but unusual ones: they are defined by a weak electric organ used for electrolocation and communication, and by a long ribbon-like anal fin that provides essentially all of their propulsion, since they lack both a dorsal fin and a conventional tail fin. Within the order, the Apteronotidae are set apart by an electric organ built from modified nerve cells rather than muscle, giving them the fastest, most continuous discharges of any knifefish family.
The species epithet montanus is Latin for 'of the mountains', referring to its type locality in the Andean cordillera foothills of Peru. The genus Sternarchorhynchus is one of the largest and least-known in the family, characterized by an elongated, downward-curving tubular snout unlike the shorter face of aquarium species such as the black ghost (Apteronotus albifrons). These New-World electric knifefishes are unrelated to the superficially similar Asian featherback and clown knifefishes (Chitala, Notopterus), a case of convergent body shape rather than kinship. The Catalog of Fishes is the authority for the valid name.
Morphology
Sternarchorhynchus montanus has the elongated, laterally compressed, blade-like body typical of ghost knifefishes, but is immediately distinguished from most relatives by its long, narrow, decurved snout — a tubular extension of the face that gives the genus its common description as 'tube-snouted' knifefish. As in all Apteronotidae, there is no dorsal fin and no true caudal fin; locomotion comes from a single long anal fin run as a travelling wave along the underside of the body, letting the fish move forward or backward with equal ease. The skin is scaleless.
Females reach a larger maximum size than males: FishBase records a maximum total length of 10 in for females against 9 in for males, a modest size for the genus. Running the length of the body is the electric organ, paired with sensory pores across the skin that read the field it produces — the sensory system this species, like its relatives, relies on far more than eyesight. Sexes are not reliably distinguished by color or pattern; the size difference noted on FishBase is the only documented external clue.
Habitat
This species is known from the Andean foothill drainages of Peru, where the type series was collected in cordillera streams — freshwater, benthopelagic habitat in the tropical zone. It is one of many narrow-range Sternarchorhynchus species restricted to a limited stretch of Andean-influenced river system rather than the wide Amazon-basin distribution seen in trade species like the black ghost.
As with other ghost knifefishes, it is presumed to favor flowing water over deep river channels and margins, active mainly at night and relying on electrolocation rather than vision in dim or turbid conditions. Specific temperature, pH and current data for S. montanus have not been published; broader Sternarchorhynchus biology points to warm, soft, near-neutral to acidic Neotropical river water, but this should be treated as generalization from the genus rather than a documented figure for this species.
Feeding
Published diet data specific to Sternarchorhynchus montanus are sparse, but the genus as a whole is well characterized: the long, decurved, tubular snout is a specialization for probing into riverbed sediment and among debris for aquatic insect larvae and small burrowing invertebrates, taken with a grasp-and-suction feeding action rather than by biting. FishBase places the species at a trophic level around 3.3, consistent with an intermediate predator of small invertebrates rather than a fish-eater.
Like other Apteronotidae, it almost certainly hunts primarily at night, using its electric sense to detect the faint electrical signatures of prey hidden in sediment or root tangles where sight is of little use. Beyond this genus-level picture, no feeding studies specific to S. montanus have been published.
Mating
No courtship or mating behavior has been documented specifically for Sternarchorhynchus montanus. What is known comes from the wider Apteronotidae, where the wave-type electric organ discharge doubles as a social signal: work on related ghost knifefishes has shown discharge frequency shifting during social encounters, forming a kind of electric 'duet' between courting fish and distinctive interruptions between rivals, with discharge frequency itself carrying information about a fish's identity and sex. It is reasonable to expect similar electric signaling plays a role in this species' courtship, but this has not been studied or confirmed for S. montanus itself.
Data on pairing, spawning site selection or any physical courtship display are entirely lacking for this species; the genus is simply too poorly observed in the wild, and it has no meaningful presence in the aquarium trade where such behavior might otherwise be recorded by hobbyists.
Breeding
Sternarchorhynchus montanus is presumed to be an egg-layer, consistent with the rest of the Apteronotidae, but no breeding has been documented in the wild or in captivity, and the species is not part of the aquarium trade. Ghost knifefishes in general are only rarely bred even under aquarium conditions, and almost all trade specimens of the family are wild-caught or farm-produced under hormonal induction rather than through natural spawning in a tank — this species has never featured in that trade at all.
Given the complete absence of reproductive data, nothing can responsibly be said about spawning site, egg number, incubation or parental care beyond the general expectation, drawn from its relatives, of scattered eggs among cover and no meaningful parental care afterward. Data sparse.
In the aquarium
Sternarchorhynchus montanus is not an aquarium fish. It is not established in the ornamental trade, and there is no body of hobbyist husbandry experience to draw on for this species, unlike its more familiar relative the black ghost knifefish. Any care information would have to be extrapolated from the genus and family, and doing so with any confidence would risk asserting details that are not actually known for this fish.
What can be said generally about ghost knifefishes applies in principle: they are scaleless and so require great care with medications, particularly avoiding copper-based treatments and reducing doses of others; they are sensitive to ammonia and nitrate and need mature, well-filtered water; and as nocturnal electrolocating predators they need cover and dim lighting to feel secure. But none of this has been verified against a captive S. montanus, and the honest position is that this species belongs to Andean field surveys and museum collections, not to home aquaria.
Conservation
Sternarchorhynchus montanus is assessed as Least Concern on the IUCN Red List, an assessment made in 2014. This reflects the absence of documented major threats rather than a well-studied, thriving population — as with many narrow-range Andean-drainage fish, the assessment is based on limited data about a species restricted to a modest stretch of Peruvian foothill streams.
Narrow-range single-basin endemics of this kind are generally the more vulnerable members of the genus when habitat change, damming, deforestation or pollution affect their limited range, even where a Least Concern listing currently applies. No specific conservation programs or threats have been documented for this species; it is not targeted by the aquarium trade, which removes one common pressure on knifefishes but leaves habitat integrity in its home streams as the main long-term consideration.