It can be found in a variety of environments, including lakes, rivers, ponds, and slightly brackish locales like lagoons.

Despite a comparatively-short reproductive period, individuals also demonstrate high fecundity, which assists in maintaining a stable population.

[7] Occasionally, nuptial tubercles (small fleshy extensions on the anal or pelvic fins of male specimens) may develop; these are sometimes bifid.

[3] Body weight and standard length are positively correlated with the relative fecundity of specimens; in other words, large individuals are more likely to be capable of reproduction.

For instance, populations of A. aeneus in the Champotón river mate the most during the stretch from April to July, and if water quality is poor, they can respond by transferring energy from the liver to increase gamete production, allowing year-round spawning.

[7] Astyanax aeneus is considered a keystone nutrient recycler, partially because of its varied appetite, and this specifically applies to phosphorus, which can limit the health of a given ecosystem (especially in neotropical streams like the ones it inhabits).

One example is the Champotón river in southwestern Mexico, which is poorly studied but is under pressure from natural phenomena (like hurricanes) and anthropogenic hazards (like agriculture).

Changes include "eye and pigmentation regression, as well as modifications in brain morphology, behaviors, heart regenerative capacity, metabolic processes, and craniofacial organization" (as described by geneticist William R.

[17] There are at least two populations of A. aeneus that are stygobitic (living solely in underground water sources, like caves or aquifers), but far more of A. mexicanus (more than 30).

[2] In turn, A. aeneus is sometimes a food source for human populations in rural areas, and is also subject to infestation by gill parasites from the flatworm family Monogenea; species include Anacanthocotyle anacanthocotyle, Characithecium costaricensis, Diaphorocleidus kabatai, Palombitrema heteroancistrium, and Urocleidoides strombicirrus.

Closely related species Astyanax cocibolca lives syntopically with A. aeneus in Lake Nicaragua.

)[22] Reportedly, A. aeneus is among the various species of Astyanax available for purchase in the aquarium trade, though their presence appears to be sparse.

[26] Astyanax aeneus is considered a species of least concern by the IUCN due to its wide range and generally adaptable nature.

Though its range was once wider due to accepted synonymy of species that are now considered separate, its population levels remain high and stable without signs of an imminent decrease or catastrophe.

[1] This may change, given its status as a cryptic species;[3] if more speciation is revealed through study, then the range of A. aeneus may shrink as different populations are renamed entirely.