Devils Hole: The Desert Cave Where a Rare Fish Survives, Nevada

In the Amargosa Desert of southern Nevada, a narrow crack at the base of a small limestone hill opens into a pool of still, blue water. It doesn't look like much from above: the surface is only about 22 meters long and a few meters wide. But below it, a flooded cavern drops into the earth. Divers have mapped it to a depth of nearly 450 feet, and the bottom has never been found. The water in Devils Hole is warm, a constant 93 degrees Fahrenheit in the deeper reaches, and low in oxygen. It's fed by groundwater moving through the limestone. Near the entrance, a small, sunlit rock shelf lies just below the surface. That shelf is the key to the only population of one of the rarest fish on Earth. The Devils Hole pupfish is a tiny, iridescent blue fish that lives nowhere else in the wild. It survives mostly in the top 80 feet of the cavern, feeding on algae that grows on the sunlit shelf, making this the smallest known range of any vertebrate species on the planet. Before the 1990s, spring counts found around 200 to 250 fish. The hole is so connected to the deep crust that distant earthquakes reach it. When large quakes strike hundreds or even thousands of miles away, the water in Devils Hole sloshes back and forth in waves, called seiches. In September 2022, a magnitude 7.6 earthquake in Mexico sent 4-foot waves through the pool. A magnitude 7.0 quake off northern California, about 500 miles away, set the water surging within minutes. The fish have always been vulnerable. In 1976, the U.S. Supreme Court protected the water level in Devils Hole to keep the habitat from being drained by nearby groundwater pumping. Since 1972, biologists from the National Park Service, the U.S. Fish and Wildlife Service and the Nevada Department of Wildlife have counted the fish nearly every spring and fall, diving to count them in the cavern while others count from the surface. In spring 2024, they counted 191 fish, the highest spring count in 25 years. Then a series of earthquakes disturbed the habitat and its food supply, and the spring 2025 count found just 38. For the first time, biologists released captive-raised pupfish from the nearby Ash Meadows Fish Conservation Facility into Devils Hole. By spring 2026, the count was back up to 77 fish, with young fish showing they were breeding again.