At the southeastern base of Deacon Peak, a crevasse in the rocks reveals the water-filled opening of a cave. Divers have descended to over 400 feet yet still have not discovered the cavern’s bottom. The water temperatures at the surface register a constant 92° F. Just below the water surface on the south end of the cave opening lying about one foot underneath is a rock shelf. The shelf measures 11.5 by 16.6 feet with the pool above measuring 11.5 by 42 feet. Welcome to the world of the Devils Hole pupfish – Cyprinodon diabolis.
RAREST OF THE RARE?
The only natural home for the Devils Hole pupfish is here. Biologists consider the species to have the smallest habitat of any vertebrate species in the world. This fact helped put up the fish as a founding member of the US Endangered Species list when it was created in 1967.
Devils Hole pupfish feed mostly on algae growing on the rock shelf. Their numbers vary with the seasons. More in spring and summer and less in winter when for several months, the sun does not touch the water’s surface diminishing algal growth. Less algae means less pupfish. Life on an 11 by 16 rock shelf remains a delicate matter no matter what the season.
The name “pupfish” comes from observations by early scientists watching the fish skittering about. The scientists likened the fish interplay to puppies. That the skittering about really was not related to “play” at all. Male pupfish chasing other fish away from their spawning grounds was initially missed by the fish discoverers. The name, however, stuck.
KILLIFISH COUSINS
Pupfish, as mentioned in an earlier post, are a killifish, members of the Cyprinodon genus. There are many other species and subspecies of pupfish beyond those here living in this cavern pond. The Devils Hole pupfish closely resemble other species of pupfish found in spring pools in the surrounding Ash Meadows National Wildlife Refuge. They are a bit smaller, less than one inch in length with a slightly larger head than their cousins. They also do not have pelvic fins. Pupfish at the Hole are less aggressive than other pupfish. But they are ever bit as much as survivors as the other pupfish species. Dissolved oxygen levels in the waters are much reduced. High water temperature, low oxygen and reduced light all in turn reduce the algal growth. Reduced food sources have been shown to reduce the size of the fish as is the case here.
THE AQUIFER
When you look down into Devils Hole, you are looking directly into an aquifer. The roof of the cavern collapsed sixty thousand years ago, creating a window to the vast underground lake. Water in the aquifer, the Ash Meadows Refuge brochure describes as “fossil water”. Coming from as far away as 100 miles to the northeast – interesting question is whether any changes to the “fossil water” has occurred secondary to the nuclear testing in the 1950-1960s – the water seeps through the ground taking literally thousands of years to reach the Amargosa Valley. A geologic fault acts as an underground dam. The waters then seep to the surface in over 50 seeps and springs mostly located in the Ash Meadows Refuge. Over 10,000 gallons per minute flow year-round from seven major springs.
PRESENT AND FUTURE
Through its springs, the aquifer provides the water source for the perennial nature of the Amargosa River, seen above ground around Beatty, Nevada and Tecopa, California. Much of the recharge of the aquifer occurs in the Spring Mountains. These mountains rise above 11,000 feet just to the west of the Las Vegas basin. The aquifer in recent years lies under siege especially from urbanization in especially the Pahrump Valley, but also Las Vegas. Pahrump’s growth to over 35,000 people pumps far more out of the aquifer than recharges fill the aquifer back up. Protection of the aquifer also remains confused because of the various agencies spread out federally and over the states of California and Nevada. Legal actions resulted in protection of water usage in the Amargosa Valley, but, again, the recharge of the aquifer comes from areas farther afield.
legalisms
While the big legal battles of the late 20th century centered around potential development in the immediate Amargosa Valley, the main problem currently lies further to the southeast in Pahrump. Driving in on Nevada Highway 160 from Las Vegas, you are greeted by various billboards advertising real estate agents. The valley also does not lie entirely within Nevada. Within the California section, a very ambitious Charleston View project looks to significantly increase the population meaning also the groundwater depletion. Both states have erratic histories when it comes to urban development. Further increases in the Pahrump Valley could easily deplete the aquifer destroying thousands of years of evolutionary development for the benefit of more single and double-wide homes. As to the legal battles entailing water more locally to Devils Hole, I send you to Kevin Brown’s excellent study Devils Hole Pupfish.
Cyprinodon diabolis
On 20 March 1891, Theodore Palmer visited Devils Hole and scooped up ten “small fish” from the pool. The fish remain preserved at the Smithsonian Institute in Washington, DC. Palmer’s actions provided the first push to create a unique species. That speciation, proving rare, subsequently influenced many of the decisions allowing the fish to survive the 20th century. Interestingly, Palmer was not in the desert looking for fish, but for birds. In his report, the episode relating to his findings in Devils Hole rated one paragraph.
Subsequent ichthyologists noted the fish Palmer – and others who followed – collected were truly unique to the Amargosa-Death Valley region. Without such a classification, the Devils Hole pupfish, as well as the other pupfish, might not have made it far into the 20th, let alone, the 21st centuries. Sometimes the collections went a bit far as in the case of the exhibit USNM 94266 located in the Smithsonian – these exhibits are only open to scientists – where the accompanying note explains the 43 specimens collected on 26 March 1930 represented 30% of the entire known species at the time of collection.
THE LITTLE FISH
The small little fish demonstrates a smaller size, absence of pelvic fins, less aggressive behavior and a low fecundity. All of these differences come about either through genetic divergence or in response to the extreme conditions found in Devils Hole. For example, other pupfish placed in conditions similar to the Hole grow in similar, smaller ways.
Like other pupfish, Cyprinodon diabolis feed mainly on algae, in this case, algae growing on the rock shelf on the south end of the cavern opening. They also will eat diatoms and small insects which have the misfortune of falling in the water. Their lifespan is only one year. They breed and lay eggs onto the shelf. Numbers of the fish vary with the season, dropping in the winter when food – algae – becomes much less with the lack of direct sunlight. Those numbers varied between 200 fish in the spring to 300-500 in the fall, though recent counts – counts are done from the surface and with scuba divers – have counted as few as 35 fish.
FISH IN A HOLE
The fish depend on water levels being maintained within the cave. Developers tried to change the landscape in the 1960-early 1970s with the development of a series of wells dug around the area hoping to bring about an agricultural transformation to the Amargosa Valley. Devils Hole found itself included into Death Valley National Monument – now Park – in 1952. President Harry Truman signed the act thinking, as did scientists of the time and many still do, the fish lived in Devils Hole for many thousands of years, becoming isolated with the shrinkage of the Ice Age lakes. Recent studies indicate the age of the Devils Hole pupfish to be of a more recent onset – hundreds instead of thousands of years. More genetic testing and comparisons with the other Amargosa pupfish are needed.
The question also arises how did the pupfish get here in the first place? The shores of the former lakes never got as high as Devils Hole for one thing. And if the age of habitation is only hundreds of years, again, how did the pupfish come to live in such an extreme environment? Some thinking utilizes either human or bird vectors bringing eggs in somehow. Native Americans had knowledge of Devils Hole far back into the past. The pupfish found in Owens Valley near Bishop, California even used to figure in the diets of Paiute tribespeople.
REFUGES JUST IN CASE
Cyprinodon diabolis’ classification in the taxonomical world lies as a distinct species today, not as a subspecies of the Amargosa pupfish family – Cyprinodon nevadensis. Isolated from other pupfish for centuries, hybridization with the Devils Hole and Ash Meadows pupfish have occurred. On a couple of occasions, concrete pools have been constructed to try and build a larger population – one at the base of Hoover Dam and another at the Point-of-the-Rocks spring to the south of Devils Hole. Accidentally, other pupfish got into the pools and breeding did occur between the outsiders and Devils Hole fish. The hybrids were considerably larger than the Devils Hole fish. Again, the question is genetics or environment?
REFUGIA
In earlier reports comparing fish taken out of Devils Hole and placed in a refugium established below Hoover Dam, increased size and a smaller head proportion became noted in comparison to the Devils Head population. Again, environment and genetics at work. While the population at Hoover Dam showed the fish to be reproducing, problems with the equipment and contamination led to the closure of the refugium though efforts appear underway to overhaul the refugium.
Refugia also went up at School Springs and Point-of-the-Rocks Springs. Equipment failure occurred at School and hybridization at Point-of-the-Rocks. At the cost of $4.5 million a 100,000-gallon refugium – Ash Meadows Fish Conservation Facility – was built about a half mile west of Devils Hole on the former site of the School Springs facility. This tank includes a replica of the Devils Hole habitat including a rock shelf replica. Work aims at building a self-sustaining population of Cyprinodon diabolis. Eggs from Devils Hole get collected and incubated at the facility. After hatching, the juveniles are raised in aquaria and stock the main tank as young adults. Neither the facilities at Ash Meadows nor Hoover Dam are open to the public.
VISITING DEVILS HOLE
Truman’s 1952 proclamation made 40 acres around the cavern entrance part of Death Valley National Monument – the Monument became a National Park in 1994. Reasoning for the proclamation noted a “peculiar race of desert fish … which is found nowhere else in the world, evolved only after the gradual drying up of the Death Valley Lake System isolated this fish population from the original ancestral stock that in Pleistocene times was common to the entire region.” The Park Service neglected the Hole for much of the first 15 years afterwards. It was only threats by developers in the Amargosa Valley when preservation of the Hole and its unique pupfish began taken more seriously eventually leading to a US Supreme Court decision ending in part the water depletion attempts.
In 1984, secondary to political movements and new threats to develop Ash Meadows into something like what has occurred in the nearby Pahrump Valley, the Ash Meadows National Wildlife Refuge developed. Ash Meadows NWR represent one of the first organized to protect endangered species – of which there are several species beyond the Devils Hole pupfish at play here. The land was acquired by the Nature Conservancy the year before with funds reimbursed by the federal government.
ASH MEADOWS NATIONAL WILDLIFE REFUGE
Ash Meadows sits west of the Longstreet Inn on Nevada Highway 373. Turn east off 373 onto Spring Meadows Road about a mile north of the Inn-Casino which is located on the California-Nevada border. Four mile of dirt road – graded and accessible by normal vehicles except for periods of rain where mud can factor in – leads to the Ash Meadows NWR Visitor Center. Another access routes you from the south off Bell Vista Road coming west from the north end of Pahrump or east from Death Valley Junction, about three miles south from the Longstreet Inn. Either way is about four miles to the Center.
The Center includes stories about the various endangered species in the refuge. At the time of our visit, it was closed because of the 2025 government shut down. There is a 0.9-mile boardwalk we walked behind the Center which loops across the alkali floor to Crystal Springs. The boardwalk sets up high enough so you cannot really see any pupfish – here, they are Ash Meadows Amargosa pupfish, Cyprinodon nevadensis mionectes – without binoculars. Afternoon winds made possible sightings even more difficult on our visit. The trail loops back to the Visitor Center along the springs outlet before recrossing the alkali.
DEVILS HOLE
Driving further on the road from the Center, you turn south until you find an intersection with the road heading east continuing on to Devils Hole – about a half mile further. For Devils Hole, park on the side and walk in on a trail-road to the fenced-off area around the collapsed cave-pool. Walking through a squirrel cage meant to keep visitors and fish separate, you come to an observation point some 40-foot above the pool.
Note the array of monitoring equipment set out to keep track of visitors, water levels, and water chemistry. Without a good pair of binoculars, you will not be able to see the fish, but you still gain a good sense of isolation.
Something to note; if you see white patches on the surface of the shelf, these are for the purpose of gathering eggs which, because of the season, would not normally hatch. Those eggs are gathered up and taken to the Ash Meadows Fish Conservation Center to replenish their stocks. You might notice the occasional pupfish skittering across the pads.
seiche
A seiche is a standing wave occurring in an enclosed body of water. They can occur in lakes, swimming pools and – important here – caves. Often imperceptible to observers, low level seiches are normally present on larger lakes but remain unnoticeable lost among other wave patterns. Seiches caused by wind can lead to seiches of up to 16 feet high at the end of Lake Eire due to wind directions and the shallowness of the lake. The effects mimic hurricane storm surges though a seiche can oscillate from one side of the lake to the other for a much longer time causing flooding in both directions.
In earthquake-prone regions, lakes remain at risk from seiches. Swimming pools demonstrate seiches induced by earthquakes which can occur locally or thousands of miles away. Such is the case at Devils Hole following a 7.6 earthquake in western Mexico about 1,500 miles away. This earthquake – 19 September 2022 – resulted in a seiche at Devils Hole up to 4 feet high. If you watch the National Park Service video of the event, you notice the back-and-forth nature of a seiche – unlike a tsunami which is a different phenomenon. This sloshing atop the surface wreaks havoc with the shallow nature of the algal shelf on which the pupfish lives depend. Other seiches have been noted in 2012, 2018, 2019 and 2024 following other earthquakes.
FINALLY, SOME PUPFISH
Backtrack and turn south – this is the road in from Bell Vista – another 0.3-mile brings you to the road going east to the Point-of-the-Rocks. This is the best spot where you can observe the pupfish – again Cyprinodon nevadensis mionectes. A short 0.5-mile boardwalk takes you through meadows created by several springs, the most obvious being at King’s Pool. Here, from the edge of the pool, look carefully down under the water to see the pupfish feeding on algae. You can also note the occasional Western Mosquitofish – Gambusia affinis. The trail continues a short way to a hilltop viewpoint looking out over the surrounding desert.
