Pupfish is the common name for small killfish that make up the Cyprinodontidae family of fish. The ray-finned fish are well-known for hardiness, and are often found in waters that most other fish would die in. There are approximately 100 different species of pupfish, most of all are found exclusively in the United States. All species of the fish are small, the biggest reaching a length of about 8 inches (22 cm), and nearly all thrive best in brackish freshwater lakes although some species are found in coastal marine areas.
As mentioned before, pupfish are routinely found in areas that most would assume would be uninhabitable for most fish. Species of pupfish have been found in the shallow, hot and extremely salty waters of Death Valley, making them the only species of fish that is known to survive in the harsh desert. These pupfish are very small, usually only growing to about 2.5 inches (6.5 cm) in length.
It is silver in appearance, with dark coloration covering its sides. The fish is scaled and its mouth is upturned, traits shared by many other species in the family. It is a short-lived species as well, and most don't make it to a full year. During the winter months is usually lies dormant by burrowing holes in the muddy waters until spring comes, which is spawning season.
Another prominent species of pupish is the Devil's Hole pupfish, named after its only known location, the Devil's Hole, a large geothermal limestone cavern found in the Amargosa Desert in Nevada. This species of pupfish is the smallest desert pupfish and is less than an inch (2.5 cm) in length. It is similar in appearance to other species of the fish otherwise, and have large dorsal and caudal fins that a blue in color, just like the body of the fish.
The water of Devil's Hole is extremely hot, usually peaking around 93 degrees Fahrenheit (33 degrees Celsius), making the pupfish one of the few fish species that is known to survive in near-boiling water conditions. Devil's Hole is the only place where this species is known to live, making it a very rare fish. Since wildlife groups began monitoring the fish in the 1990s the maximum population observed has been around 500 and numbers have dropped as low as 38. Efforts to help maintain the population by introducing a foreign food supply seems to have helped stem off further declines.