Orestias (fish)

Orestias is a genus of pupfish. Older systematics classified them into the own family Orestiidae. They are found in lakes, rivers and springs in the Andean highlands of South America, and several species are considered threatened. They are egg-laying fish that feed on small animals and plant matter. The largest species can reach a total length of , but most remain far smaller. Their most characteristic feature is the absence of the ventral fin, although this is shared by a few other pupfish. Despite their moderate to small size, they are important to local fisheries and a few species are farmed. Several species are locally and colloquially known as carache. The name of the genus is a reference to Orestes, a Greek mythological character who Valenciennes described as the "nymph of the mountains". Orestias is restricted to freshwater habitats at an altitude of in the Andes of central and southern Peru, western Bolivia, and northeastern Chile. 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. Of the 45 recognized species of Orestias, the majority are found in Lake Titicaca (including 23 endemics to its basin), with the remaining from other Altiplano lakes, rivers or springs. 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 ), and some pelagically in the open water. Orestias species found elsewhere than Lake Titicaca often have very small ranges. Relatively little is known about the behavior of Orestias. They feed on small crustaceans (such as amphipods and cladocera), aquatic insects and larvae (such as chironomids), snails, small fish, fish eggs, algae, macrophyte seeds and plant detritus.