Taxonomy & naming
Astyanax bourgeti was described by Carl H. Eigenmann in 1908, in the Bulletin of the Museum of Comparative Zoology at Harvard College, the same paper that introduced several related species including A. anterior, A. asymmetricus, and A. symmetricus. The valid name, as maintained in Eschmeyer's Catalog of Fishes (California Academy of Sciences), is Astyanax bourgeti Eigenmann, 1908. Because the species was described within Astyanax and remains there, no parenthetical is used around the authority.
Astyanax is the largest genus in the family Characidae and one of the most species-rich vertebrate genera in the Americas, spanning an enormous range from Texas to Patagonia. The genus has long been a subject of taxonomic study, and species boundaries within it remain an active area of revision. FishBase notes the family placement as Acestrorhamphidae in some recent treatments of American tetras, but the Catalog of Fishes and the original description place the species in Characidae, which is the family used here per the site's data standard.
Morphology
Astyanax bourgeti is a typical small Astyanax in body plan: a moderately deep, laterally compressed, silver-bodied characid with the standard complement of fin rays for the genus. Eigenmann's original morphometric data, as summarised by FishBase, record a head length fitting 3.33 times into standard length and a body depth fitting 2.33 times — proportions indicative of a somewhat deep-bodied but not extreme form within the genus.
The most readily noted external character is the black pigmentation of the lower fins, recorded as distinctive in the original description and noted in the FishBase account. Fin-ray counts recorded for the species include D.11 and A.34, the latter (a long anal fin) being characteristic of many Astyanax species. Beyond these points, morphological data on the species in the published literature are sparse, and detailed meristic tables are not widely reproduced outside the original 1908 work.
Habitat
Astyanax bourgeti is a freshwater, benthopelagic species endemic to the upper Amazon basin, with the type locality in the Amazonas main-channel drainage. FishBase classifies the species as tropical and benthopelagic, indicating a tendency to occupy mid-water to near-bottom zones in slow or standing water rather than fast-flowing rocky streams.
Detailed field ecological data for this species specifically are not well documented in the accessible literature. As a member of the upper Amazon fauna, it inhabits a region characterised by warm, often soft and slightly acidic waters typical of lowland Amazonian rivers, though the exact microhabitat preferences of A. bourgeti within that system have not been formally described. The IUCN assessment notes that the species is not well studied for either conservation threats or the aquarium trade, but records it as widely distributed within the upper Amazon.
Feeding
FishBase records a trophic level of 2.9 for Astyanax bourgeti, placing it in the lower-omnivore range and consistent with the broad omnivory typical of the genus. Astyanax species as a group are opportunistic feeders that consume small invertebrates, plant material, algae, and particulate organic matter depending on availability, with diet composition varying by season and locality.
No species-specific dietary study of A. bourgeti is available in the accessible literature. By analogy with better-studied congeners — including the well-researched A. mexicanus and various South American Astyanax — the species is expected to feed on microinvertebrates, insect larvae, zooplankton, and plant matter in proportion to local abundance. The relatively high population resilience noted in the FishBase account (minimum doubling time less than 15 months) is consistent with the energetic efficiency of omnivorous feeding strategies.
Mating
No published study of reproductive behaviour specifically for Astyanax bourgeti is available. The genus Astyanax as a whole reproduces by egg-scattering, and all well-studied Astyanax species are non-guarding open spawners that scatter adhesive eggs among fine-leaved vegetation or substrate without forming pair bonds or providing any parental care.
Males in Astyanax species typically pursue females and initiate spawning drives in the water column or among plants. Spawning in the wild is thought to be triggered by rainy-season conditions — rising water levels, cooler temperatures, and increased food availability — as is common across Characidae. Absent species-specific field data, A. bourgeti is assumed to follow this general Astyanax reproductive pattern.
Breeding
Astyanax bourgeti has not been documented in the aquarium hobby literature as a species bred in captivity, and no dedicated husbandry account exists for it in accessible sources. Based on the reproductive biology of the wider genus and of Characidae generally, breeding would be expected to follow the pattern common to Astyanax: egg-scattering over fine-leaved plants or a substrate, adhesive eggs that hatch within 24 to 48 hours at tropical temperatures, and free-swimming fry that initially require very fine foods such as infusoria or rotifers before graduating to newly hatched brine shrimp.
Parental care is absent in Astyanax, and adults will consume their own eggs if left with them; breeders of related species routinely separate spawning adults from the eggs immediately after spawning. The high population resilience index recorded for the species (minimum doubling time less than 15 months, per FishBase) is consistent with a reproductive strategy of frequent, relatively large spawns rather than few large-investment eggs — the typical pattern for small characids.
In the aquarium
Astyanax bourgeti is essentially unknown in the mainstream aquarium hobby. No commercial imports or dedicated breeding programmes are documented, and it does not appear in the trade literature or specialist hobbyist resources. It is a scientific name in the ichthyological literature rather than a fish available to aquarists at present.
Should the species become available, the broad husbandry template of the genus Astyanax would apply: a spacious, well-filtered aquarium with warm (75–82 °F), soft to moderately hard water and a slightly acidic to neutral pH, kept in a school of six or more, and fed a varied omnivore diet of quality flake, micro-pellets, and frozen or live invertebrates. The black-finned coloration noted in the original description could make it an attractive aquarium subject, but its availability is presently nil outside scientific collection.
Conservation
Astyanax bourgeti is assessed as Least Concern (LC) on the IUCN Red List, with the assessment dated 04 March 2021. The listing reflects the species' apparently wide distribution within the upper Amazon basin and the absence of documented population-level threats sufficient to qualify it for a threatened category. The IUCN assessment notes that the species is not well studied and is not recorded from the aquarium trade.
The upper Amazon basin, while not uniformly pristine, still supports large areas of intact freshwater habitat, and wide-ranging Amazonian characids are generally considered resilient compared with range-restricted endemic species. Continued monitoring of Amazonian freshwater biodiversity remains important as deforestation, mining, and dam development affect river systems across the region, but no specific threat targeting A. bourgeti has been identified in the literature.