Genus · Tetras

Astyanax

Astyanax is a genus with 152 species in this atlas, catalogued in the Tetras section, recorded from Brazil, Argentina, Colombia and 18 more countries. Adult sizes run from 1 in to 10 in. Every species below links to a full researched profile.

Species in atlas: 152
Adult sizes: 1–10 in
IUCN assessed: 152 of 152 · 16 threatened
Recorded from: 21 countries

About the genus

Astyanax is a large genus of characins in the tetra family Characidae, found across freshwater habitats from the southern United States borderlands down through Mexico and Central America into much of South America. The atlas covers 152 species, with strongest representation in Brazil, Argentina, Colombia, Mexico, Peru, Bolivia, Guatemala and Venezuela, reflecting a genus that has diversified into nearly every river system on the continent. Most species share the classic tetra silhouette: a laterally compressed, silvery body with a forked tail, though many carry a dark humeral spot or shoulder mark and a stripe along the flank. Adults range from about 1 in in the smaller stream species up to roughly 10 in in the largest river forms, considerably bigger than the tetras most aquarists picture.

A number of Astyanax are established in the aquarium and pond trade under names like the banded tetra (A. aeneus) and the yellowtail tetra (A. altiparanae), valued as hardy, adaptable schooling fish that tolerate a wider range of water conditions than many South American tetras. Because the genus is so widespread and includes so many superficially similar silver species, taxonomy within Astyanax has a long history of revision, and species boundaries in some regional groups are still debated. Conservation status is mixed and, for many species, simply unassessed. The atlas tally includes a substantial Data Deficient and Not Evaluated share alongside smaller numbers of Vulnerable, Endangered and Critically Endangered species, consistent with a genus whose diversity is still being sorted out.

IUCN Red List: Critically Endangered · 3 Endangered · 4 Vulnerable · 9 Near Threatened · 8 Least Concern · 56 Data Deficient · 26 Not Evaluated · 46

The 152 species

Every Astyanax recorded in this atlas. Each card links to a full researched profile — distribution, water parameters, and aquarium care, cited to primary sources. 1 has hobbyist breeding reports (◉).