Rare Pupfish Population Jumps From 20 to 77 in Death Valley

A tiny blue fish swimming in a sunken pool of hot water in Death Valley just got a lifeline that worked beyond scientists' wildest hopes.

The Devils Hole pupfish lives in one of the world's smallest habitats for any vertebrate: a single cavern pool in Death Valley National Park where 93-degree water has been their only natural home for thousands of years. Last year, their population plummeted to a terrifying 20 fish.

Wildlife managers made an unprecedented decision. For the first time in the species' conservation history, they released captive-bred pupfish from a backup population into Devils Hole, starting with 19 fish and later adding 50 more.

The gamble paid off. This spring, biologists counted 77 fish swimming in the cavern.

"We're breathing a lot easier at 77 than 20," says Olin Feuerbacher, a biologist with the U.S. Fish and Wildlife Service who manages the backup population. The drop was especially shocking because just months earlier, in fall 2024, the population was booming at 212 fish after several years of strong growth.

Scientists have been preparing for this moment since 2013, when they started breeding pupfish in a massive 100,000-gallon tank designed to perfectly replicate Devils Hole. The tank sits at the Ash Meadows Fish Conservation Facility and has served as an insurance policy for over a decade.

"It's in our strategic plan as an option but it's one that nobody really wanted to talk about because we never thought that we would be in that position," Feuerbacher explains. Releasing captive fish into the wild isn't done lightly since captive populations differ slightly from wild ones.

The Bright Side

The successful introduction shows that careful long-term planning can save even the most vulnerable species. Death Valley National Park biologist Kevin Wilson notes that Devils Hole is "probably the smallest known habitat for a vertebrate species," with nutrient-poor, oxygen-poor water that most fish couldn't survive in.

Scientists have spent decades protecting these iridescent little fish with fences and video surveillance. Since 2007, they've added supplemental food to the water to help the population thrive.

"I think we saved the species," says Michael Schwemm, another Fish and Wildlife Service biologist involved in the effort.

The pupfish's survival in such an inhospitable environment has long fascinated researchers and the public alike. Now, thanks to quick action and years of preparation, this conservation icon has a fighting chance to rebuild its population in the wild where it belongs.