They are found in lakes, rivers and springs in the Andean highlands of South America, and several species are considered threatened.

[8] Orestias is restricted to freshwater habitats at an altitude of 2,800–4,600 m (9,200–15,100 ft) in the Andes of central and southern Peru, western Bolivia, and northeastern Chile.

[2] Although freshwater habitats at low and middle altitudes in the Andes are relatively rich in fish, few are found in the highest, with Orestias and the catfish Astroblepus and Trichomycterus being the primary—in many places only—native genera.

[2] In addition to differences in feeding, the many species in Lake Titicaca segregate by habitat preference, with some living among totora reeds, some among submerged macrophytes, some at the bottom in water too deep for macrophytes (deeper than 10 m or 33 ft), and some pelagically in the open water.

[3][11][12] There are significant variations depending on exact species, especially in Lake Titicaca where there is a degree of niche differentiation, including some that mainly feed on zooplanktonic organisms, two (O. albus and O. cuvieri) that are particularly willing to take other fish, primarily smaller Orestias (fish eggs are regularly consumed by a wider range of species), several that mainly feed on small bottom- or plant-living organisms, and some that are generalists that will feed on a wide range of things,[3][4][10][12] sometimes varying depending on season.

[13][14] In the 1960s, an expedition to Lake Titicaca led by Jacques Cousteau reported seeing many dead Orestias and when studied they were found to be infected by a disease introduced with the trout.

[18][19] Despite their moderate to small size, some species are important to local fisheries, but they are overfished, there are few regulations and limited enforcement of the rules that do exist.

[14] Because of pollution, studies have revealed levels of metals in Orestias of Lake Titicaca that exceed the internationally recommended safety thresholds for human consumption.

[21] O. agassizii and O. luteus are also farmed and spawned in captivity; both to supply the food market and for release to support their vulnerable wild populations.