The Devils Hole pupfish is one of the world’s most unique species of desert pupfishes. It has survived in Devils Hole, a submerged cave system that provides a window into the aquifer, for at least hundreds and possibly tens of thousands of years. Devils Hole pupfish have a beautiful, iridescent blue color that stands out against the stark landscape of Devils Hole. Males especially exhibit this striking coloration, which can appear particularly vibrant during breeding seasons. Additionally, this is the only pupfish known to lack an entire set of fins— the pelvic fins.
Despite the harsh conditions in Devils Hole, the Devils Hole pupfish has a natural food source. They eat algae, microorganisms, and aquatic invertebrates that live in the water. However, the warm water, low dissolved oxygen, and nutrient-poor environment limits the diversity of these organisms within the spring. The water in the deeper areas of the cave is consistently 92-93 degrees Fahrenheit (33-34 degrees Celsius) and can be even warmer in shallower areas. Further, sunlight only hits the water surface part of the year. All these characteristics coalesce to provide one of the most inhospitable habitats for any fish species.
The pupfish spawn on a single shallow rock shelf just under the water’s surface that provides critical habitat for the fish.. This shelf is only about 2 meters wide by 6 meters long— not much larger than a medium-sized walk-in closet! It is often said that the Devils Hole pupfish has one of the most restricted habitats of any vertebrate species.
The plight of the Devils Hole pupfish has attracted both national and international attention. In addition to its state (Nevada) and federal (United States) endangered species status, the International Union for Conservation of Nature (IUCN) includes the Devils Hole pupfish on its Red List of Threatened Species as “Critically Endangered”. Additionally, in 1976 the United States Supreme Court established a minimum water level requirement for Devils Hole to help ensure the species’ persistence in the wild.