After Recent Earthquakes Decimated Devils Hole Pupfish Population, Captive-Bred Fish Added For First Time

Recent earthquakes caused a “sudden population decline” in Devils Hole pupfish — the world’s rarest fish, found only in Death Valley — but park officials say they are on the path to recovery thanks to the introduction of captive-raised fish.

This spring, National Park Service (NPS), U.S. Fish and Wildlife Service (USFWS), and the Nevada Department of Wildlife conducted a semiannual survey of the Devils Hole pupfish population in the limestone cavern where they live in Death Valley National Park. They found just 38 fish, compared to 191 in spring 2024.

Officials say two recent earthquakes, in December 2024 and February 2025, triggered waves in Devils Hole moving fish eggs, algae and other organic material off a shelf at the caverns entrance that serves as a spawning habitat and food source.

For the first time, captive-raised fish were added to the wild population. In addition to adding a total of 19 fish, biologists used data from the captive Devils Hole pupfish population to determine how to supplement the wild population’s diet until the algae could regrow.

“Im proud of the work of this interagency team to monitor and protect the Devils Hole pupfish,” Death Valley National Park Superintendent Mike Reynolds said in a statement. “The historic transfer of captive-raised fish from the backup population in Ash Meadows Fish Conservation Facility underscores the importance of the dedicated staff and their state-of the-art equipment.”

Since 1972, biologists have counted the Devils Hole pupfish population every spring and fall, both by SCUBA diving into the cavern and counting from the surface. Until the mid-1990s, more than 200 fish were counted each spring. In the early 2000s, they found an average of around 90 pupfish, until the population suddenly declined to just 35 in 2013. After climbing again in recent years, the population reached a 25-year high in 2024.

“The present size at near-record lows deserves our serious attention, and the actions in the strategic plan, including supplemental feeding and population augmentation, provide the best opportunity for recovery,” said Michael Schwemm, senior fish biologist for USFWS.

Pupfish eggs have been regularly collected from Devils Hole and used to establish the captive population to ensure the survival of the species.

Biologists say conditions in Devils Hole are improving this spring breeding season, with natural food sources returning with the spring sunlight.

“The fish were in good body condition and active throughout Devils Hole,” said NDOW Supervising Fisheries Biologist Brandon Senger. “Seeing fish exhibiting spawning behavior was really encouraging, as was the increase in algal growth.”