Taxonomy & naming
Chilobrycon deuterodon was described by Jacques Géry and Laurent de Rham in 1981. It is the only species in the genus Chilobrycon, a monospecific placement that itself signals how distinctive and geographically isolated this fish is — there is no cluster of close congeners to compare it against, only the species itself and its narrow home range.
The cached sources place it within the broader minor-characin assemblage rather than among the well-known piranhas, pacus or silver dollars of Serrasalmidae. As with much of this group, the finer points of its taxonomic placement rest on the Catalog of Fishes (Eschmeyer, California Academy of Sciences) as the standing authority for the valid genus and species combination; nothing in the cached research suggests a pending revision or synonymy for Chilobrycon deuterodon.
Morphology
Chilobrycon deuterodon is a small characin, with FishBase recording a maximum published length of 4.5 in standard length for male or unsexed individuals — modest by the standards of the wider "Piranhas & Pacus" assemblage, which also contains fish that reach a metre or more. No female-specific maximum size is documented in the cached sources.
Detailed morphological description — body shape, fin structure, colouration — is not covered in the available cache. Data on these traits is sparse in the accessible literature, and rather than guess at field marks this account limits itself to what the sources actually confirm: a small-bodied, pelagic freshwater characin restricted to a single Peruvian river drainage.
Habitat
The species is endemic to the Tumbes River drainage on the Pacific slope of northern Peru, confirmed independently by FishBase, the IUCN Red List, iNaturalist occurrence records and OBIS occurrence data. This is a Pacific-draining system rather than part of the Amazon or Orinoco basins that host most of the characins in this atlas — an important distinction, since Pacific-slope drainages in this part of South America are short, comparatively small watersheds with limited connectivity to neighbouring river systems.
FishBase classifies it as a tropical freshwater pelagic species. Beyond that classification, specific data on preferred microhabitat, water chemistry and seasonal behaviour within the Tumbes drainage is sparse in the cached sources; this account does not speculate beyond what has been documented.
Feeding
No diet data for Chilobrycon deuterodon was found in the cached research. FishBase and the other cached sources do not document stomach-content studies or field observations of feeding behaviour for this species specifically.
Given the sparse documentation, no diet claim is made here rather than extrapolating from other, better-studied minor characins. Prospective keepers or researchers should treat feeding ecology as an open question pending further study.
Mating
Courtship and pairing behaviour for Chilobrycon deuterodon is not documented in the cached sources. No dedicated aquarium or field account of spawning behaviour, sexual dimorphism, or courtship display was located.
As with several other data points for this species, the honest position is that this remains unrecorded in the accessible literature rather than a trait that can be inferred from its more thoroughly studied relatives.
Breeding
Breeding mode and parental care for Chilobrycon deuterodon are not documented in the cached research. There is no evidence in the available sources of aquarium breeding, commercial propagation, or field-observed spawning behaviour for this species.
Given how narrow and specialised its native range is, and the complete absence of an aquarium care profile (SeriouslyFish, for instance, has no dedicated entry for it), it is reasonable to treat this species as essentially unknown in captive breeding terms. This account does not assign a breeding mode by analogy to other minor characins, since doing so would risk misrepresenting a fish that may never have been bred or even closely observed spawning.
In the aquarium
Chilobrycon deuterodon has no dedicated aquarium care documentation in the cached sources — SeriouslyFish, the usual reference point for hobby care profiles of minor characins, has no species-specific entry for it, and none of the other cached sources address tank size, water parameters for captive care, or compatibility. It does not appear to be an established aquarium trade fish.
What can be said with confidence is that its modest adult size (4.5 in SL maximum) would not, on its own, rule out a modest home aquarium, in contrast to many other genera in this group that outgrow standard tanks entirely. But without documented water-chemistry or behavioural data, any specific stocking or care recommendation here would be guesswork rather than grounded advice — this account declines to invent one.
Conservation
The IUCN Red List assesses Chilobrycon deuterodon as Near Threatened (NT), an assessment carried out by T.J. Lyons and dated 17 July 2020, under criterion B1ab(iii) — a criterion tied to a small, restricted range combined with an observed, estimated, inferred or projected decline in the extent, area or quality of habitat. The core driver of concern is straightforward: the species is confined entirely to the Tumbes River drainage on the Pacific slope of northern Peru, so any degradation of that single watershed affects the entire known population.
The cached sources do not detail specific threats such as damming, water abstraction or pollution within the Tumbes drainage, but single-river endemism of this kind is inherently precarious regardless of the exact pressure, since there is no second population elsewhere to buffer a local decline. There is no evidence in the cached sources of a significant aquarium trade in this species, so collection for the hobby does not appear to be a relevant conservation factor here.