The desert pupfish (Cyprinodon macularius) is a small fish, less than three inches long, with a rounded body shape and silvery background with narrow dark vertical bars on the sides. A remarkably tolerant species, it can survive high temperatures and salinities, including low dissolved oxygen concentrations. It feeds on invertebrates, plants, algae, and detritus.

Populations of naturally occurring desert pupfish are only found in two stream tributaries to, and in shoreline pools and irrigation drains of the Salton sea in California. It also naturally occurs in Mexico. The desert pupfish is a federally endangered species.