A biological puzzle surrounds how the Devil’s Hole Pupfish has endured for decades in a spa-like cavern enclosed by a bare granite mountain in Death Valley National Park.
The lowest geographic range of any vertebrate, the shallow end of an oxygen-deprived pool 10 feet wide, 70 feet long, and more than 500 feet deep, is home to the world’s rarest, most inbred fish.
Biologists believed the species, long seen as a representation of the desert conservation movement, would become extinct within a year as its numbers fell to 35 at the beginning of 2013.
But since then, the fish has managed to pull itself back from the edge, reaching a total population of approximately 475 this spring the busiest time for breeding in both the wild and in captivity.
“It gives me goose bumps knowing that their numbers have risen,” said Kevin Wilson, aquatic ecologist for Death Valley National Park. As he gazed into the exposed aquifer that has been their home since perhaps the end of the Ice Age, scores of the inch-long iridescent blue fish were browsing lazily, or nipping at each other’s tails.
“The ranks of Devil’s Hole pupfish have swelled to numbers high enough,” Wilson said, to attempt the previously unthinkable: collecting samples of gut contents, fin clippings and tissue from live specimens for DNA sequencing. With management plans that take diseases and complex genetic features into consideration, this knowledge could assist increase survival rates.
Such treatments were not feasible when the population was in danger of going extinct. As a result, putrefied tissue samples from dead pupfish that National Park Service employees gathered were used in laboratory experiments.
“The prospect of providing answers to old mysteries makes the bumper crop of pupfish even more gratifying,” Wilson said.
If this fish went extinct on my watch. I’d be haunted for the rest of my life by this question: ‘What didn’t I do?’Kevin Wilson
Among basic questions that remain unresolved: Exactly how and when did the fish end up in the pool, about 90 miles northwest of Las Vegas?
With a lifespan of 12 months and the lowest genetic diversity ever documented in the wild, what are its chances of surviving continuing threats from flash floods, earthquakes and the Mojave Desert’s changing climate?
Within 15 minutes of an earthquake somewhere in the world, waves as high as 6 feet tall wreak havoc upon the fish’s isolated domain.
A 2015 genetic study led by Christopher Martin, a professor at the University of California, Berkeley specializing in the origins of biodiversity, referenced previous research suggesting that the probability of Devil’s Hole pupfish extinction within 50 years exceeded 80%.
“It’s exciting to see that this fish is doing well and not going to go extinct in a few years,” Martin said.
“We want to know as much as we possibly can about them,” he added. “So, as their numbers improve in the wild and in the facility, we can begin to think about raising a colony in the laboratory.”
Michael Schwemm, a senior fish biologist for the U.S. Fish and Wildlife Service, agrees. A pupfish revival, he said, “allows more opportunity for study and to explore new management options.”
A strategic management plan created by wildlife officials restricts human encounters with wild Devil’s Hole pupfish. It would only permit intrusive study if the population reached 300 or more for three straight years.
“It may be time to adjust those rules,” Wilson said.
Despite a decadeslong rescue effort however, the Devil’s Hole pupfish lives a solitary life in the turquoise waters of a subterranean fissure at the bottom of a limestone depression that makes protecting it a challenge.
The secret to its existence is an ancient 23-square-yard block of rock that protrudes into the pool just a few feet below the surface. The slab where the fish spawn is coated in a thin layer of green algae meadows, which are their main food supply.
Females lay their eggs in the geothermically heated pool that has been a constant 93 degrees, which is approaching the upper physiological limit for the species.
In 1952, President Harry S. Truman had the unique fish and its pocket ecology added to Death Valley as a protective measure.
The Devil’s Hole pupfish thrived until the late 1960s, when the water level and the numbers of fish began to fall precipitously because of irrigation pumping.
Conservationists, who wanted to stop the pumping to save the fish, and townspeople, who placed a higher priority on economic growth, engaged in a classic environmental conflict as a result of the population crash.
Two popular bumper stickers at the time declared “Save the Pupfish” and “Kill the Pupfish.” The dispute resulted in a significant 1976 ruling by the U.S. Supreme Court upholding federal groundwater rights over the fish’s vulnerable habitat.
Federal officials surrounded the pit with 10-foot fencing topped with barbed wire, surveillance cameras, and radio antennas in an effort to protect the fish’s future. But the pupfish’s troubles were far from over.
Subsequent decades saw a gradual decline in population and the pupfish crisis of Sept. 11, 2004: Empty fish traps had been stacked by researchers on dry land, but a flash flood sent them tumbling into the pool. The traps ended up on the shelf with 80 expired fish in them.
Later, a trespassing incident led to the arrests of three men on felony charges in connection with a drunken rampage at Devil’s Hole, where a pupfish was found dead. They left behind plenty of evidence: beer cans, underwear, vomit, a cellphone and a wallet.
In 2013, a panic set in when it seemed extinction was imminent. Wildlife authorities installed clumps of aquarium plants where babies could hide from predatory adults.
In a collaborative effort involving the U.S. Fish and Wildlife Service, the National Park Service and the Nevada Department of Wildlife, biologists collected a batch of Devil’s Hole pupfish eggs and took them to the newly constructed Ash Meadows Fish Conservation Facility nearby.
The facility includes research tanks and a $4.5 million 100,000-gallon tank constructed as a duplicate of the natural rock tub. Their objective was to create a captive colony of the fish there.
Now, “we’re developing plans to breed large numbers of Devil’s Hole pupfish,” said Jennifer Gumm, manager of the facility.
In the meantime, Devil’s Hole pupfish in the wild still face serious problems due to their precarious life cycle and the environmental extremes that visit their hellish habitat.
“If this fish went extinct on my watch,” said Wilson, “I’d be haunted for the rest of my life by this question: ‘What didn’t I do?’”