Devils Hole Pupfish

Cyprinodon diabolis

## Basic Info

The **Devils Hole pupfish** (*Cyprinodon diabolis*) is a critically endangered species of the family Cyprinodontidae (pupfishes) found only in Devils Hole, a water-filled cavern in the US state of Nevada. It was first described as a species in 1930 and is most closely related to *C. nevadensis* and the Death Valley pupfish (*C. salinus*). The age of the species is unknown, with differing analyses offering ranges between one thousand and sixty thousand years. It is a small fish, with maximum lengths of up to 30 mm (1.2 in). Individuals vary in coloration based on age and sex: males are bright metallic blue while females and juveniles are more yellow. A defining trait of this species is its lack of pelvic fins. The pupfish consumes nearly every available food resource at Devils Hole, including beetles, snails, algae, and freshwater crustaceans, with diet varying throughout the year. It is preyed on by the predaceous diving beetle species *Neoclypeodytes cinctellus*, which was first observed in Devils Hole in 1999 or 2000. Reproduction occurs year-round, with spikes in the spring and fall. Females produce few eggs, though, and the survivorship from egg to adult is low. Individuals live 10–14 months.

Devils Hole is more than 130 m (430 ft) deep, though pupfish are only found in the upper 24 m (80 ft). The water is a constant temperature of 33 °C (91 °F) and dissolved oxygen levels are low. A small, shallowly submerged rock shelf provides critical feeding and spawning habitat for the pupfish. Nearby agricultural irrigation in the 1960s and 1970s caused the water to drop in Devils Hole, resulting in less and less of the shelf remaining submerged. Several court cases ensued, resulting in the Supreme Court case *Cappaert v. United States*, which determined that the preservation of Devils Hole as a National Monument in 1952 implicitly included preservation of adequate groundwater to maintain the scientific value of the pool and its fauna. Other threats faced by the species include flash floods, earthquakes, and vandalism.

Devils Hole Pupfish sign

As its entire native range is a single locality, efforts to create other populations have proceeded since the 1960s and 1970s, most of which have failed. Three refugia were created in 1972, 1973, and 1990, though all were closed by 2007 as a result of maintenance failures, hybridization, and small founder populations. In the early 2010s, an exact replica of the uppermost 6.7 m (22 ft) of Devils Hole was constructed at Ash Meadows Fish Conservation Facility, which was populated with eggs taken from Devils Hole in winter months when development into adults is unlikely. Efforts to conserve the wild population have included removing sediment from the shallow shelf, adding supplemental food, and installing fences and security cameras to keep unauthorized people away. Conservation efforts have been costly and divisive. During the legal battle over ground water in the 1960s and 1970s, bumper stickers were distributed that read "Kill the Pupfish" or "Save the Pupfish". Some have argued that the species should be allowed to go extinct, while others have said this would be akin to "bombing the Louvre to make way for a parking lot".

Population counts are conducted twice a year, in the spring and fall, with the fall population usually much larger. Since 1972, population counts have peaked at around 550 individuals. The April 2013 count showed only 35 remaining in the wild, but by April 2022, the count showed a total of 175 observed wild pupfish. The Devils Hole pupfish has been listed as endangered by the US federal government since 1967 and critically endangered by the International Union for Conservation of Nature since 2014.