| Devils Hole pupfish | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Cyprinodontiformes |
| Family: | Cyprinodontidae |
| Genus: | Cyprinodon |
| Species: | C. diabolis |
| Binomial name | |
| Cyprinodon diabolis Wales, 1930 |
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The Devil's Hole pupfish, Cyprinodon diabolis, is a species of fish native to Devil's Hole, a geothermal (92 °F/33 °C), aquifer-fed pool within a limestone cavern, in the Amargosa Pupfish Station of the Desert National Wildlife Refuge Complex east of Death Valley National Park.
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The Devil's Hole Pupfish is the smallest desert pupfish species in the Cyprinodon Genus.
Devil's Hole pupfish are less than 25 millimeters (1 in) long and resemble other pupfish in shape. They are the smallest of the desert pupfish species, averaging 19 millimetres (0.75 in) in length. They lack pelvic fins and have large heads and long anal fins. Breeding males are solid deep blue and have a black band on the caudal fin.
Devil's Hole and the pupfish are located in the Amargosa Desert ecosystem, in the Amargosa Valley, of southwestern Nevada, USA, east of Death Valley and the Funeral Mountains and Amargosa Range. The Amargosa River is part of Devil Hole's and the region's aquifer hydrology.
Devil's Hole pupfish have been the subject of considerable attention and litigation, due to their ancient origins, unusual habitat and precarious existence. A 22-thousand-year-old species, these pupfish depend on a shallowly submerged limestone shelf of only 2 metres (6.6 ft) by 4 metres (13 ft) in area for spawning as well as for much of their diet (primarily diatoms). Natural threats from flash floods to earthquakes have been known to disrupt this fragile ecosystem, but the major threat has been groundwater depletion due to agricultural irrigation.
C. diabolis was first noticed in 1890 but only identified as a unique and highly divergent species by Joseph Wales in 1930. Formal protection of the species began in 1952 when Devils Hole was made part of Death Valley National Monument (now Death Valley National Park). Endangered species designation occurred in 1967, followed by the formation in 1969 of the Desert Fishes Council to fight agricultural interests for the protection of the fish. Water rights litigation went all the way to the US Supreme Court who in the 1976 Cappaert v. United States decision ruled against neighboring land developers.
A number of artificial "refugia" (concrete tanks approximating conditions in Devil's Hole) have been established to ensure species survival should the natural population at Devil's Hole die out: one at Hoover Dam established in 1972 (reported 2004 population, 79), and two near Devil's Hole itself within the Ash Meadows National Wildlife Refuge established in 1980 and 1991 that comprise the Amargosa Pupfish Station (with populations fluctuating between 90 and 120 depending on season).
In May 2005, nine pupfish were moved from the hole and a federal hatchery to both a Las Vegas Strip casino aquarium, at Mandalay Bay, and another federal hatchery in hopes of augmenting the population.[2]
In November 2005, divers counted just 84 individuals in the Devils Hole population, the same as the spring population, despite observations of egg-laying and baby fish during the summer. As many as 80 fish – one third of the population – was estimated to have been destroyed during the summer of 2004 when a flash flood pushed a quantity of scientific equipment (fish traps) into the hole; later about 60 cubic feet (1.7 m3) of debris, washed into the cave by floods, was removed. Reasons for the continued decline are primarily related to the continued removal of the pupfish and their relocation to refugia where the population has either died, cross bred with other species, or evolved into a unique species. In 2008, the pupfish began to be fed a special food to attempt to restore the population. In May 2009, the National Park Service announced that the latest count of pupfish ranged from 56 to 83, with an average of 70. While this population is well below the genetic viability limit of 200 pupfish (estimated by fish biologists during the Cappaert litigation), it is an improvement of the 2008 average of only 45 pupfish.
Five younger pupfish were moved to the Willow Beach National Fish Hatchery in Arizona in order to establish the pupfish in aquaria. 36 adults are believed to still reside in the hole after the moves. Willow Beach National Fish Hatchery no longer has Pupfish.
In 2007 there were between 38 and 42 fish left in Devils Hole.[3] The Devils Hole pupfish count rose in the autumn of 2008 to one hundred twenty six, the first steady increase in more than ten years.[4] The average number of pupfish estimated in April 2011 was 104.[5]
The natural population at Devils Hole fluctuates depending on the season.[6] Low algae growth and other winter conditions cause spring populations to range only from 150 to 250; while they swell to 400 to 500 individuals in the Autumn.[7] All the various surviving local Cyprinodon species and subspecies (Pupfish), including the Devils Hole pupfish, are on the IUCN Red List - endangered species.
Several other populations of Devils Hole pupfish have been established in artificial refuges that mimic the environment of Devils Hole, with only limited success. These populations also fluctuate by season and are monitored regularly. The Amargosa Pupfish Station includes Devil's Hole and others, all in the Ash Meadows National Wildlife Refuge, within the larger Desert National Wildlife Refuge Complex, which along with the Devils Hole-Ash Meadows, also includes the Moapa Valley National Wildlife Refuge, the Desert National Wildlife Refuge, and the Pahranagat National Wildlife Refuge.
The water level in Devils Hole is monitored daily by the National Park Service and occasionally by the U.S. Geological Survey. During the late 1960s, the water level dropped dramatically in response to pumping in the Ash Meadows area, in the immediate vicinity of the cavern. After the cessation of pumping near Devils Hole, the water levels recovered until about 1986, when the water level began to decline. Pronounced changes in the water level resulted in response to the 1992 Landers/Little Skull Mountain earthquakes and the 1999 Hector Mine earthquake. Since December 2005, the water level in Devils Hole has been rising and, by December 2008 the water level had risen to its highest level since 1993. That the water level has risen in spite of the fact that water use has increased in the region suggests that climate and other factors may have a greater impact on the water level in Devils Hole than groundwater pumping.
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