10
Loading video...
By Emma Marsden
Reporter
0
Share
Newsweek is a Trust Project member
See more of our trusted coverage when you search.Prefer Newsweek on Googleto see more of our trusted coverage when you search.
One of the world's rarest fish is making a remarkable comeback after its population plunged to dangerously low levels, prompting conservationists to intervene.
The Devils Hole pupfish is a tiny, endangered fish found naturally in just one location in the world. Biologists counted 137 fish during a National Park Service survey on October 10—nearly double the 77 recorded in spring 2026, the NPS said.
During the fall survey, divers and surface observers from the National Park Service and U.S. Fish and Wildlife Service counted fish both in the cavern's deeper waters and along the shallow limestone shelf where they feed and reproduce. The agencies have used these monitoring methods to track the population since 1972.
Read More on News
The latest reported figures also represent more than twice the 69 fish counted in fall 2025, offering fresh hope for a species that recently faced the prospect of extinction.
Newsweek contacted the National Park Service via email on Monday for comment and awaits a response.
Where Does the World's Rarest Fish Live?
The rare species lives exclusively in Devils Hole, a water-filled limestone cavern within Death Valley National Park in Nevada. The park spans parts of both California and Nevada. The entire wild population of the pupfish depends on an extraordinarily small habitat; this makes it particularly vulnerable to environmental changes.
The tiny fish measures just 0.9 inches long on average, with the largest recorded specimen reaching 1.7 inches. Males develop a striking, iridescent blue coloring, particularly during spawning, while females are generally olive-green.
...
How Does the Devils Hole Pupfish Survive?
The species has evolved to survive in an unusual environment. Water temperatures in the cavern remain between approximately 91 and 93 degrees Fahrenheit (33 to 34 degrees Celsius) throughout the year. Oxygen and nutrient levels are relatively low, creating an environment in which relatively few fish could survive.
The fish spend much of their time feeding on algae and tiny invertebrates growing on a shallow limestone shelf. Measuring just 215 square feet, the shelf is also where the pupfish reproduce and lay their eggs.
That dependence on such a small area makes the species especially susceptible to disruption.
What Caused the Pupfish Population to Decline?
In December 2024 and February 2025, earthquakes triggered waves inside Devils Hole, washing away algae, organic material and fish eggs from the shelf. The disruption contributed to a dramatic population decline, with biologists counting just 38 fish during the spring 2025 survey, compared with 191 a year earlier. The total included 19 captive-raised fish released into Devils Hole in an emergency conservation effort.
In response, conservationists took the unprecedented step of releasing captive-raised Devils Hole pupfish into their natural habitat. Between March 2025 and February 2026, 72 fish were transferred from the Ash Meadows Fish Conservation Facility, which maintains a backup population to help prevent the species from becoming extinct.
Scientists also provided supplemental food while algae recovered.
...
Conservation Efforts Help World's Rarest Fish Recover
The latest survey suggests those efforts are paying off. Given that Devils Hole pupfish typically live for just 10 to 14 months, biologists believe most of the 137 fish counted in October were born and raised inside the cavern, rather than being among the captive-bred fish released there.
However, the recovery remains fragile.
An earthquake in Panama on October 9, almost 3,000 miles away, initially caused signs of stress among the fish. Although they appeared healthier during a subsequent visit, the incident highlighted how vulnerable their isolated habitat remains to disturbances thousands of miles away.
While the latest increase is encouraging, officials say continued monitoring, research and habitat management will be essential to ensuring the Devils Hole pupfish survives for generations to come.
"It's exciting to see Devils Hole pupfish numbers increase so significantly over the past year," said Death Valley National Park Superintendent Mike Reynolds.
"These results reflect the dedication of our scientists and conservation partners working to protect this extraordinary species. While challenges remain, we're encouraged by this progress and committed to its long-term survival."
Contact Newsweek editors on this story: John Fitzpatrick and James Debens
View 0 Comments
Submit Correction
View Editorial & AI Guidelines