Taxonomy & naming
Acestrocephalus boehlkei was described by the Brazilian ichthyologist Naércio A. Menezes in 1977 in the journal Papéis Avulsos do Departamento de Zoologia (São Paulo), volume 30, number 13, pages 185–193, under the title 'Acestrocephalus boehlkei, a new and disjunct Cynopotamine from Ecuadorean and Peruvian Amazon.' The type locality is the Punino River, a tributary of the Payamino River in the Napo drainage, collected above the town of Coca, Ecuador. Paratypes included material from the same drainage, among them a mature male of 3.5 in standard length deposited at the Museu de Zoologia da Universidade de São Paulo (MZUSP 12993).
The genus Acestrocephalus belongs to the subfamily Cynopotaminae, a group of characteristically elongated, predatory characids distributed across tropical South America. Eschmeyer's Catalog of Fishes recognises Acestrocephalus boehlkei Menezes, 1977 as the valid name; the authority is not parenthesised because the species was originally described in Acestrocephalus, the genus where it still resides. The species has a notably disjunct distribution across the upper Amazon system — a pattern that Menezes noted in the original description title and that the IUCN assessment subsequently confirmed across the Madre de Dios, Urubamba, Ucayali, Marañón, Napo-Pastaza, and broader Amazon basins of Peru and Ecuador, with possible records from Venezuela.
Morphology
Acestrocephalus boehlkei reaches a maximum recorded standard length of 5.5 in — a figure consistent with the predatory Cynopotaminae, which tend toward slender, torpedo-shaped bodies suited for pursuit hunting in current. The body is elongated and laterally compressed, with a pointed snout, a large mouth armed with sharp teeth, and a forked caudal fin. Like other cynopotamines it has the characteristic large eyes and streamlined profile that mark an active, visual predator in clear water.
Detailed meristic and morphological data were established by Menezes in the original 1977 description. The species lacks the bold lateral stripe that marks some of its congeners and is distinguished from related Acestrocephalus species by a combination of characters including fin-ray counts, body proportions, and dental arrangement. Coloration in life is not extensively documented in the available literature; the fish is likely silvery to pale with the subdued, countershaded pattern common to open-water characid predators of clear streams. Sexual dimorphism, if present, is not described in detail in the sources consulted.
Habitat
Acestrocephalus boehlkei occupies fast-flowing, clear streams at elevations of approximately 150 to 350 metres above sea level across the upper Amazon basin. The IUCN assessment describes the habitat as streams with gravel substrates and bank vegetation — conditions typical of Andean-foothill and sub-Andean drainages where current velocity remains high and dissolved oxygen is correspondingly elevated. The water is clear rather than black or white, suggesting moderate to low tannin load and reasonable transparency.
The confirmed drainage systems include the Punino River (Napo system, Ecuador), and records extend across the Napo-Pastaza basin of Ecuador and into the Madre de Dios, Urubamba, Ucayali, and Marañón basins of Peru, with possible occurrence in Venezuela. This relatively wide foothill distribution, yet at restricted elevation bands, places the species in habitat that is vulnerable to Andean deforestation, agriculture, and oil-extraction activity — the same pressures the IUCN flagged as localised threats in its 2014 assessment.
Feeding
As a cynopotamine, Acestrocephalus boehlkei is a predator rather than the opportunistic omnivore that characterises most popular aquarium tetras. The genus Acestrocephalus is adapted for piscivory and invertebrate predation: the elongated body, large mouth, and sharp dentition are all consistent with pursuit hunting of smaller fishes and large invertebrates in clear, fast water. Specific stomach-content data for this species are not widely reported in the accessible literature, but the subfamily ecology strongly indicates a diet dominated by small fish and large aquatic invertebrates.
In captivity, Cynopotaminae generally require meaty foods and do not thrive on dry-only diets. Live or frozen fish, large invertebrates, and meaty frozen foods such as river shrimp or silversides are more appropriate than standard flake. The species is not suited to a community aquarium with smaller fishes that would be regarded as prey.
Mating
Specific mating behaviour for Acestrocephalus boehlkei has not been described in the available literature. As a member of the Characidae, the species is presumed to be a broadcast spawner like the majority of the family — releasing adhesive or semi-adhesive eggs among fine-leaved vegetation, submerged roots, or gravel, with no parental care following spawning. Sexual behaviour in predatory characids typically involves brief courtship chases, with the male pursuing a gravid female before simultaneous release of eggs and sperm.
The cynopotamine breeding season in the wild is thought to align with seasonal water-level and temperature fluctuations in sub-Andean drainages, though precise spawning triggers for this species are undocumented. The presence of mature males at 3.5 in SL in the type-series paratypes suggests the species reaches reproductive maturity at a relatively modest size relative to its maximum length.
Breeding
There are no published accounts of Acestrocephalus boehlkei being bred in captivity in the sources available for this article. Given the general biology of Cynopotaminae and related predatory characids, breeding would likely require a large aquarium, conditioning with live or meaty foods, and possibly a simulated seasonal trigger — a drop in temperature, increased water flow, or a water change simulating rainfall — to prompt spawning. Eggs, if the pattern of the subfamily holds, would be scattered and adhesive, deposited among vegetation or substrate, with no parental care and a risk of egg cannibalism by the adults.
The species' rarity in the hobby and its predatory nature make captive breeding reports unlikely to be widespread. Aquarists interested in attempting to breed it should consult experience with related cynopotamines such as Roeboides or other Acestrocephalus species, which follow broadly similar reproductive patterns, and be prepared for the possibility that data on incubation period, fry size, and first foods remain undocumented for this particular taxon.
In the aquarium
Acestrocephalus boehlkei is an uncommon aquarium fish, encountered mainly through specialist importers dealing in unusual South American characids rather than through mainstream retail. Its predatory nature makes it unsuitable for community tanks with small fish; it should be housed only with species of similar or larger size that it cannot consume. A biotope-style setup replicating sub-Andean clear streams — clean, well-oxygenated water, moderate to strong current, a gravel or sand substrate, and minimal decor that does not impede open swimming — is the most appropriate approach.
Water quality must be excellent: as a clear-stream species from fast-flowing habitats, it is likely sensitive to organic load and poor oxygenation. The IUCN reports the species from elevations of 492–1148 ft, suggesting it may be more comfortable at slightly lower temperatures than many lowland Amazonian species — a range in the low-to-mid 20s Celsius is plausible, though precise aquarium data are sparse. Feeding should consist of meaty live or frozen foods. Because the species is rarely kept and seldom written about by hobbyists, keepers should treat available care information as provisional and observe their fish closely to refine husbandry.
Conservation
Acestrocephalus boehlkei is assessed as Least Concern (LC) on the IUCN Red List, with the evaluation published in 2016 and based on an assessment dated 8 October 2014. The assessors noted a stable population and no major threats to the species as a whole. However, they identified localised habitat modification from agriculture, livestock grazing, and oil extraction as pressures on parts of the range — threats consistent with the ongoing degradation of Andean-foothill stream systems across Ecuador and Peru.
The species' relatively wide distribution across multiple drainages in Ecuador and Peru — and possibly Venezuela — gives it a broader buffer than a single-drainage endemic would have, which underlies the LC assessment. Nevertheless, sub-Andean clear-water streams are among the more threatened freshwater habitats in the upper Amazon basin, and localised declines are possible even where the species-level status remains favourable. No specific conservation measures are recorded for A. boehlkei, and its commercial rarity in the aquarium trade means collection pressure is not a significant factor.