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Devils Hole Pupfish

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Updated November 2013... The Devils Hole pupfish (Cyprinodon diabolis) was listed as endangered in 1967. This iridescent blue inch-long fish's only natural habitat is in the 93 degree waters of Devils Hole, located within the Ash Meadows National Wildlife Refuge, Nye County, Nevada, which is a detached unit of Death Valley National Park.

Photo: Devils HoleA count in April 2013, estimated 35 Devils Hole pupfish remain in their natural habitat.  A September count estimated 65 fish. These record low spring and fall counts indicate that this small, inch-long, iridescent blue fish could now be at significant risk of extinction.

A Harsh Environment

Devils Hole pupfish is one of the world’s rarest fishes, spending most of its life in the top 80 feet of the 93 degree waters of cavern in the middle of the Mojave Desert. Its habitat is one of the smallest natural ranges known for any vertebrate. 

Devils Hole is an extreme environment, with water temperatures and dissolved oxygen concentrations near their lethal limits for fish. It is thought this fish has survived and adapted to these harsh conditions for thousands of years.

Although the surface of the Devils Hole pool is small, it is an aquifer over 400 feet deep that is linked to groundwater important to Nevada and California. Scientist have recently discovered a connection with Devils Hole to earthquakes thousands of miles away.   In 2012, violent pressure waves (mini-tsunami) were recorded in Devils Hole as a result of earthquakes as far away as El Salvador and Mexico.

The Downward Trend

Endemic species with limited distribution like the Devils Hole pupfish are at greatest risk of extinction since they do not have the flexibility to change locations to adapt to changing environments. 
This short-lived species (approximately one year) has a natural high and low cycle, with the population in the fall decreasing from 35-65 percent in the spring due to natural die-off.  When population counts began in 1972 pupfish numbered around 550 individuals.

From the late1970’s through 1996, the population appeared to be relatively stable with an average count of 324 individuals.  In 1997, fall counts started to indicate a downward trend for unknown reasons.  The number of pupfish counted from 1997 to 2004 declined from an average of 275 individuals to 171 fish.  A count conducted in November 2005 indicated 84 individuals, and an April 2006 count of only 38 adult pupfish, the lowest count on record at that time.  A dive into Devils Hole in September 2006 resulted in 85 adult pupfish indicating they were recruiting and reproducing in their natural environment.

Over the next six years the number of pupfish initially increased to 126 fish as supplemental feeding began, but has since declined again. The September 2012 count of Devils Hole pupfish determined the number of pupfish had dropped to an estimated 75 fish followed by the spring 2013 count that resulted in an all-time low count of 35 fish. 

The lowest fall count on record of 65 fish occurred in the fall 2013.  This fall count is predicted to drop in spring of 2014 by 35-65 percent, consistent with the species population trends, bringing Devils Hole pupfish even closer to extinction.

The reason(s) for the decline of Devils Hole pupfish is unclear. The environment in Devils Hole has changed in a variety of ways, some of which scientists do not fully understand. Although the Devils Hole environment is small, changes can be subtle and complex, making it difficult to identify specific factors influencing the fish’s population from year to year.

Efforts To Stop The Decline

A Management Oversight Team that includes the Service, National Park Service and the Nevada Department of Wildlife, is evaluating possible processes to analyze the risk of future management options that may be implemented. Possible short-term actions for 2013 include:

1) Keep feeding pupfish in Devils Hole;
2) Increase early life state pupfish (ELS) hiding cover on the shallow shelf using artificial and natural cover packets;
3) Do a survey of ELS every two weeks to ascertain reproduction;
4) Prepare the Ash Meadows Fish Conservation Facility (AMFCF) to accept eggs, ELS or adult pupfish; and
5) Move pupfish eggs to the AMFCF to reduce the risk of extinction by establishing an additional population outside of Devils Hole.

Establishing A Refuge Population

Previous attempts to maintain captive populations of pure Devils Hole pupfish in 2006 and 2007 failed.  A captive hybrid population of Ash Meadows Armargosa pupfish crossed with Devils Hole pupfish, however, has continued to thrive and remains at Shark Reef at Mandalay Bay.

Biologists are hopeful a new Ash Meadows Fish Conservation Facility will more closely mimic the conditions in Devils Hole will provide a stable environment to establish a refuge population of the species.
The Service and its partners have developed protocols and procedures for operation of the facility and the scientific work it will host. This includes protocols (when, how, why, etc.) for moving pupfish, including their eggs and larvae, from Devils Hole to the man-made habitat in an attempt to establish a captive population. 

The first eggs were successfully moved to the facility this fall.  As of November 2013, some larvae have successfully hatched and are feeding and growing at the facility.

The Regulations

The Endangered Species Act (ESA) was enacted in 1973 to ensure protection for species determined to be threatened or endangered with extinction. The law does not provide for the abandonment of conservation actions on behalf of any listed species. Devils Hole pupfish has been at the forefront of, and has played a pivotal role in conservation in the past 50 years.  It has become an iconic species for conservation, much like the bald eagle, the polar bear, and the blue whale.

In 1976, the U.S. Supreme Court ruled a Presidential Proclamation issued to establish Devils Hole as a National Monument reserved water rights necessary to the purposes of the monument, including preservation of the pool and its fish. 

Devils Hole pupfish was listed as endangered in 1967.

Why Does It Matter

Devils Hole pupfish has much to teach scientists about adaptation to adverse conditions. It has adapted to survive in very warm water with very low oxygen content. 

Envision each living thing on Earth, including humans, as being a thread in a piece of cloth. Each time a species goes extinct, a thread is removed and the fabric is weakened. As more threads disappear, one-by-one, the strands separate and fall away. Eventually, the original piece of cloth falls apart and disappears.

All living things are part of a complex, often delicately balanced network called the biosphere. The earth’s biosphere, in turn, is composed of countless ecosystems, which include plants and animals and their physical environments. No one knows how the extinction of organisms will affect the other members of its ecosystem, but the removal of a single species can set off a chain reaction affecting many others.  Only time will tell.

If you would like additional information about the Devils Hole pupfish and recovery actions, please contact the Las Vegas field office at 702-515-5230


Last updated: May 23, 2018