Taxonomy & naming
Sternarchorhynchus kokraimoro was described by Cristiano Moreira de Santana and Richard P. Vari in 2010, one of many Sternarchorhynchus species the pair described or redescribed as they revised the genus. It belongs to the family Apteronotidae, the ghost knifefishes, within the order Gymnotiformes — the New-World electric knifefishes, a group of bony fish defined by an electric organ and a single long anal fin used for propulsion rather than a tail. Apteronotidae are set apart within the order by an electric organ built from modified nerve cells rather than muscle tissue, which produces an unusually fast, steady wave-type discharge and the most refined electrolocation of any knifefish family.
The genus Sternarchorhynchus is large — 32 recognized species — and characterized by a long, tubular, downturned snout; it accounts for roughly two-fifths of all Apteronotidae species, and more than two-thirds of its species are restricted to the Amazon basin and the neighbouring Tocantins drainage. The species epithet honours the Kokraimoro, a group within the Kayapó people whose ancestral lands include the type locality on the Xingu. As with all valid names in this family, the Catalog of Fishes (Eschmeyer, CAS) is the taxonomic authority. Despite the shared common name "knifefish", Sternarchorhynchus and its relatives are not related to the Asian featherback or clown knifefishes (Chitala, Notopterus), which belong to an entirely different order and only resemble gymnotiforms by convergent body shape.
Morphology
Sternarchorhynchus kokraimoro is a small, elongate, laterally compressed fish reaching about 8 in total length in males and unsexed individuals, with females slightly smaller at around 6.5 in — modest even by the standards of a genus of generally slender-bodied fish. Its most obvious feature, shared with the rest of the genus, is a long, tube-like snout that curves downward, an adaptation for probing into crevices and coarse substrate for hidden prey rather than hunting in open water.
As in all ghost knifefishes it has no dorsal fin and no functional tail fin; locomotion comes from a long anal fin run in travelling waves along the underside of the body, letting it move forward or backward with equal ease. The skin is scaleless, and an electric organ runs the length of the body beneath a field of sensory pores that read the weak electric field it generates — the basis of the refined wave-type electrolocation typical of the family. Specific details of coloration and fin proportions for this species are not well documented in the available literature.
Habitat
The species is known only from the Rio Xingu in Pará state, Brazil, specifically the rapids at Cachoeira de Kaituká — its type locality and, as far as recorded collections show, the only place it has been found. This is fast, turbulent, rocky river habitat rather than the still backwaters or flooded forest more often associated with Amazonian fish, and it places S. kokraimoro among the many Sternarchorhynchus species that are narrow-range endemics tied to a single stretch of river.
FishBase classifies it as a freshwater, benthopelagic species of tropical rapids, living and foraging near the riverbed in fast-flowing water. Beyond that classification, published detail on its specific microhabitat, water chemistry or seasonal movements is sparse — consistent with a poorly-studied, single-locality rapids specialist rather than a well-collected species.
Feeding
Direct dietary data for Sternarchorhynchus kokraimoro is not available, but FishBase places the species at a trophic level of 3.3±0.3, consistent with a carnivore feeding on small invertebrates rather than on plant matter or detritus. This fits the pattern for the genus as a whole: Sternarchorhynchus species use their long, downturned snouts to probe benthic sediment and rock crevices for aquatic insect larvae and other small invertebrates, locating prey largely through electrolocation in the fast, often turbid water of rapids and river channels where vision is of limited use.
As a rapids-dwelling species, it likely forages close to the substrate among rocks rather than in open water, working the same kind of habitat, and probably by the same means, as its better-documented relatives in the genus. Specific feeding behaviour and any dietary breakdown for this species have not been published; the picture above is inferred from the genus rather than confirmed for S. kokraimoro itself.
Mating
Nothing specific to Sternarchorhynchus kokraimoro has been published on courtship or spawning behaviour. As in other ghost knifefishes, the wave-type electric organ discharge almost certainly plays a role in social signalling — encoding identity, sex and possibly reproductive state — since this is well established across Apteronotidae and is one of the defining features of the family's electrosensory system. Whether this species shows the kind of frequency-shifting electrical courtship documented in better-studied relatives such as the brown ghost knifefish is not known.
Data on this species' reproductive biology is sparse to the point of being essentially absent from the literature; any account of its mating behaviour beyond the general pattern for wave-type Apteronotidae would be speculation rather than fact.
Breeding
There is no published record of Sternarchorhynchus kokraimoro breeding in captivity, and the species does not appear to be established in the aquarium trade at all — it is a poorly known, single-locality rapids fish rather than an ornamental species. Ghost knifefishes as a family are egg-layers that spawn among cover such as roots and crevices, generally without substantial parental care, but this species' own reproductive mode, spawning triggers and any parental behaviour are undocumented.
Given how little is known even about its basic biology, breeding data for this species should be treated as data sparse rather than filled in from assumption; nothing here should be read as a viable protocol.
In the aquarium
Sternarchorhynchus kokraimoro is not a species found in the aquarium hobby. It has no documented history in the trade, and as a narrow-range rapids endemic collected — as far as is recorded — only from a single site on the Rio Xingu, it is unlikely to appear as anything but an occasional scientific specimen rather than a commercially available fish.
Were it ever to be kept, the general husbandry principles that apply to its family would still hold: as a scaleless gymnotiform it would need careful attention to water quality and medication dosing (no copper-based treatments, and reduced doses of anything harsh), a nocturnal, electrolocation-driven lifestyle suited to dim lighting and secure cover, and — given its rapids origin — well-oxygenated, flowing water rather than a still tank. None of this has been tested for the species specifically, and it should not be treated as a care sheet.
Conservation
The IUCN Red List assesses Sternarchorhynchus kokraimoro as Vulnerable, an assessment from 2018 driven by its extremely restricted known range: the species is recorded only from the rapids at Cachoeira de Kaituká on the Rio Xingu, a single-locality distribution that leaves it inherently exposed to any disturbance at that site. Narrow-range endemism of exactly this kind is common among Sternarchorhynchus species, many of which are tied to single rivers or even single rapids within the Amazon and Tocantins basins.
The Xingu has been the focus of major hydroelectric development, most notably the Belo Monte dam complex, which has altered flow regimes and rapids habitat across large stretches of the river; rapids-dependent, single-site endemics are exactly the kind of species most exposed to that sort of change, though no site-specific impact assessment for S. kokraimoro itself is cited in the available sources. Its status should be read as a reflection of extreme range restriction rather than of any documented population decline.