Taxonomy & naming
Acestrorhynchus isalineae was described by the Brazilian ichthyologist Naércio Menezes and the French ichthyologist Jacques Géry in 1983. It belongs to the genus Acestrorhynchus, the pike characins, which older literature sometimes placed within Characidae but which is now treated as its own family, Acestrorhynchidae, within the characiform radiation. The genus is defined by an elongate, compressed body, a long jaw armed with prominent canine-like teeth, and a predatory, pursuit-based lifestyle that sets it apart from the deep-bodied, omnivorous or herbivorous serrasalmids (piranhas, pacus and silver dollars) that share its broader neighbourhood in the characin family tree.
As with several range-restricted Acestrorhynchus species, published information on A. isalineae specifically is sparse outside of the original description and aggregator databases such as FishBase; there is no substantial secondary taxonomic literature reviewing the species since 1983. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the governing authority for the valid name and genus placement, and nothing in the available sources suggests a synonymy or reclassification affecting this species.
Morphology
Acestrorhynchus isalineae is a small member of its genus, with FishBase recording a maximum standard length of 4 in — modest even by the standards of the pike characins, several of which exceed 8–12 in. Like its relatives it carries the characteristic Acestrorhynchus build: a slender, laterally compressed, torpedo-like body built for rapid acceleration, a pointed head with an underslung or terminal jaw lined with well-developed teeth, and a deeply forked tail. The trophic level recorded for the species (around 3.8) places it as a mid-level predator consistent with a diet of smaller fish.
No detailed account of colour pattern or fin morphology beyond the genus-typical form is available in the cached sources; the common name "striped barracuda tetra" implies the longitudinal banding typical of several congeners, but a dedicated colour description was not found and should not be asserted beyond that. As with other Acestrorhynchus, the skin and fins are thin and easily torn, a practical point covered further under "In the aquarium".
Habitat
Acestrorhynchus isalineae is known from the Rio Madeira basin in Brazil, one of the Amazon's largest southern tributaries. Beyond that basin-level distribution, the cached sources do not provide a detailed account of its specific microhabitat, so no claim is made here about channel versus floodplain preference or substrate association.
Water conditions reported for the species are warm and mildly acidic to near-neutral: roughly 75–82 °F and pH 6.0–7.5, with moderate hardness (18–215 ppm reported in the aquarium literature). These figures are consistent with typical Amazonian lowland river conditions rather than extreme blackwater, though the range quoted is broad enough that it should be read as an aquarium-keeping guideline rather than a precise field measurement.
Feeding
Acestrorhynchus isalineae is an obligate piscivore — a fish-eating predator, not an omnivore that can be coaxed onto flake or pellet as a staple. In the wild this almost certainly means pursuit or ambush predation on smaller fish sharing its habitat, consistent with its recorded mid-level trophic position.
In the aquarium this translates into a genuinely demanding feeding requirement: the species needs live or thawed (frozen) whole fish, and keepers are specifically cautioned against substituting feeder fish sourced from unclean stock (disease risk) or fatty mammalian and avian meat, which is nutritionally inappropriate for a fish adapted to a fish-based diet. Weaning an obligate piscivore like this onto prepared foods is difficult and not reliably documented for this species.
Mating
No courtship behaviour specific to Acestrorhynchus isalineae is documented in the available sources. Pike characins as a group are big-water, open-habitat fish, and nothing in the cache describes pairing, territoriality or breeding conditioning for this species.
Breeding
Acestrorhynchus isalineae has no established aquarium breeding record. What is documented for the genus and reflected for this species is an open-water broadcast spawning strategy with no parental care — eggs are released and fertilised in open water rather than deposited on a guarded nest or substrate, the pattern typical of big-river pursuit predators such as the payara and other Acestrorhynchus. This is consistent with the general pattern for large-river predatory characins, which are essentially not bred in the home aquarium.
Given the complete absence of hobbyist or commercial breeding reports for this species, any specimens in the trade should be assumed to be wild-caught, and prospective keepers should not expect to breed it.
In the aquarium
Acestrorhynchus isalineae is one of the more approachable pike characins on paper because of its small adult size — around 4 in — but it remains a fast, nervous, obligate predator that is a poor fit for a typical community tank. It is a strong jumper and requires a securely covered aquarium with generous open swimming space; a tight lid is not optional. Juveniles are reported to school, but individuals become progressively more solitary with age, and cannibalism is a real risk if a group contains fish of noticeably different sizes — keepers maintaining a group should aim for even sizing and adequate room to disperse.
The species is generally described as peaceful toward tankmates too large to be swallowed, but its obligate-piscivore diet means anything small enough to fit in its mouth is at risk, and its skin and fins are thin and prone to damage from rough handling, sharp decor or aggressive tankmates — net captures should be handled gently, ideally with a soft container rather than a mesh net. Because it needs live or thawed whole fish rather than prepared foods, it is a genuinely higher-commitment fish to feed correctly than most community characins, and its complete lack of an aquarium breeding record means the hobby depends on wild-collected stock.
Conservation
The IUCN Red List assesses Acestrorhynchus isalineae as Least Concern, an assessment dated 2018. As a narrow-range endemic of the Rio Madeira basin rather than a widespread Amazonian generalist, its LC status should be read as a reflection of currently adequate population data and no known major threats, rather than an indication that the species faces the same negligible pressure as basin-wide fish; the Madeira basin itself has been substantially affected by large hydroelectric dam construction in the past two decades, though no assessment tying that development specifically to this species' population trend was found in the available sources.
No aquarium-trade collection data or export volume specific to this species is available in the cached sources, so no claim is made about trade pressure beyond noting that, absent any captive-breeding record, all specimens reaching the hobby are presumed wild-caught from the Madeira system.