It only exists in a water-filled cavern whose bottom has never been found, a mysterious creature prowling mysterious depths. 

The thing is small, averaging around an inch in length — about the size of a paperclip. 

It’s the world’s rarest fish, an endangered species, with only around 170 of them remaining in their natural habitat at last count in 2019. 

They live in but one place on Earth: A geothermal pool in Nevada’s Amargosa Valley, about 90 miles northwest of Las Vegas, with the heavy metal-worthy handle "Devils Hole."

Behold the Devils Hole pupfish, the thing that (probably) should not be, a luminous blue minnow whose lifespan averages between 10-12 months, which can survive in its low-oxygen waters by going hours without the stuff due to a process called paradoxical anaerobism. 

“It’s a cool adaptation,” said Frank van Breukelen, professor and director of UNLV’s School of Life Sciences, who participated in the research that discovered this pupfish's unique technique. “They don’t live very long if they’re in Devils Hole, but they live long enough. Evolution was never about anything that was best, it was really about what was simply good enough.” 

That this curious creature continues to chart its unique course in the animal kingdom, though, is due in large part to the efforts of another UNLV professor: renowned biologist and environmentalist James Deacon, who passed away in 2015 at age 80. 

Beginning in the late ’60s, Deacon fought to preserve the Devils Hole pupfish’s only habitat, which would later become part of the Ash Meadows National Wildlife Refuge, a battle that went all the way to the U.S. Supreme Court. It’s a story that encapsulates one of modernity’s great debates, as civilizations continue to expand into areas once untouched by humankind: to develop or not develop? 

And at what cost? 

“Devils Hole pupfish is a great example of what’s been happening over the last 50 years, really, to biodiversity on Earth,” Deacon said in a 2006 interview done by the UNLV Oral History Research Center as part of its UNLV at 50 Oral History Project. “And it will continue to be — provided it survives.” 

Save the pupfish! Kill the pupfish! 

If it wasn’t for a research project on the fish of the Southwestern United States six decades ago, the Devils Hole pupfish might not be here today. 

James Deacon wrote said paper while he was a grad student at the University of Kansas, hipping him to the region. He’d then be hired at UNLV in 1960. 

“As soon as I got here, I began looking around for getting a research program started, and the first place to go was Ash Meadows,” Deacon recalled in a 2008 interview for the Boyer Early Las Vegas Oral History Project. “The most fascinating species was this little guy that occurred in only one place: Devils Hole.” 

Why was it so fascinating? 

In part large because its entire native range is confined to a single locality, the smallest range of any vertebrate, making it incredibly vulnerable to extinction. As such, it would become one of the first species protected under the Endangered Species Act in 1967. 

That same year, however, cattle ranch Spring Meadows, Inc. began purchasing tracts of land in Ash Meadows. 

“Spring Meadows immediately started developing their irrigated agriculture and one of the wells that they drilled was within about two feet of the 40-acre boundary of Devil’s Hole, on their land,” Deacon said in the interview. “They did a test pump, and it was as if they had a pipe directly to Devils Hole.” 

In the years that followed, water levels dropped at Devils Hole, threatening its pupfish. 

Deacon helped found the Desert Fishes Council, an organization formed, in part, to protect the species. In 1971, the U.S. Department of Justice took Spring Meadows Inc. to court to stop the company from using a trio of wells negatively impacting Devils Hole, eventually earning an injunction in favor of the government in 1973 as the case worked its way to the Supreme Court in 1976.

Public opinion, though, remained hotly divided on the issue. 

In a scathing editorial on March 8, 1976, the Elko Daily Journal Free Press brands preservationists “ruckus-makers,” dismissing as “silly” and “insidious” their efforts to save the “tiny fish that no one can ever see.” The piece culminates by suggesting that the piscicide rotenone be used to eradicate the “problem” fish. 

Nevertheless, in the landmark case Cappaert v. United States the Supreme Court upheld the injunction. 

The Devil’s Hole Pupfish was saved — at least for time being. 

A hard-fought future 

In 1980, Ash Meadows was sold to a property development company, Preferred Equities Corp., which planned to build a large housing tract on the land. 

“Preferred Equities started by saying, ‘Let’s develop this in a way that won’t do a lot of damage so that we can actually have a development,” Deacon recalled in the 2008 interview. “They asked me to help them identify some of the things that they could do, and that turned out to be just a nightmare.” 

Deacon recalled a meeting with the company’s owner, who took him out in the field and boasted that he was going to build himself a house incorporating rare natural artifacts in his living room. 

“This guy will never get it,” Deacon remembered thinking at the time. 

But after some protected pupfish were found dead in the area, Preferred Equities was shuttered in 1982, according to The Mojave Project documentary and curatorial series. 

The nonprofit group Nature Conservancy raised enough money to buy the land from Preferred Equities, in cooperation with the U.S. Fish & Wildlife Service, and in 1984, the Ash Meadows National Wildlife Refuge was born, which is currently home to at least two-dozen plants and animals found nowhere else in the world. 

Including the Devils Hole Pupfish. 

Keeping an eye on the pups

How many of them exist today? 

The official numbers currently are unknown, as biologists have been unable to do their normal twice-a-year count due to the pandemic. In September, however, they’ll dive into Devil’s Hole once more and resume their work in the field. 

The species is being maintained, in part, at the U.S. Fish and Wildlife Service’s Ash Meadows Fish Conservation Facility, where new pupfish are born in a series of tanks, including one designed to mimic the conditions of their native habitat. 

For van Breukelen, the efforts to maintain the pupfish population resonates beyond said species: In the battle to preserve Devils Hole, the Ash Meadows Refuge was created. 

And so in saving the pupfish, dozens of other species have met with the same fate. 

“I think the most important thing that’s happened conversation-wise is not just Devils Hole, it’s the conservation of all of Ash Meadows,” van Breukelen said. “The efforts in order to try to expand and restore Ash Meadows has been tremendous. 

“Ash Meadows is the number one spot for endemism in North America," he said, referring to when a species is solely found in a single geographic region. "There’s more unique species in Ash Meadows than there are anywhere else in North America.

"That’s pretty frightening to think that that was close to being made into a housing tract.”