General: Pupfish (Cyprinodon) and Poolfish (Empetrichthys) are small, minnow- or guppy-like fish that live in springpools and streams in the Mojave Desert; some even live in the bottom of Death Valley. All of these species are in danger of extinction.

During the last ice age (which ended only about 10,000 years ago), what is now the desert was wetter and cooler, and streams and lakes were common in the bottom of most large valleys. Even Death Valley was covered by a huge lake. A few species of fish lived in the streams and lakes, but most were lost when the climate changed and the desert dried out.

Some species, however, were small enough and hardy enough to survive in the small streams that remained after the lakes dried up. As the streams dried further, some of these fish found themselves isolated in the spring pools and short outflow streams that once fed the larger streams and lakes.

The pupfish habitat we see today (small, isolated springs and streams) is left over from the large, interconnected ice-age streams and lakes. As a result of drying and isolation, the remaining small populations of fish have speciated, and in most places where they occur today, the species are unique to each place.

One species, the Devils Hole Pupfish, occurs only in Devils Hole, a tiny spot of water at the bottom of a hole. This species has the smallest habitat of any animal in the world.

Several pupfish refugia have been established around the southwest. A refugia is a place where humans have built ponds, tanks, or large aquariums and stocked them with pupfish and other small desert fish. There is a refugia at Boulder Dam that I have never seen, and there is another at Corn Creek on the Desert National Wildlife Range that is open to the public.