The Devils Hole pupfish, a tiny iridescent fish that lives only in a single warm, oxygen-poor pool in Death Valley National Park, narrowly avoided extinction after an emergency release of captive-bred fish. Kept behind fences and under constant watch, the species has survived in that rocky “fishbowl” for millennia. But about a year ago the wild population crashed suddenly to roughly 20 individuals, forcing managers to use a preexisting refuge as an emergency lifeline.
Biologists moved quickly. Staff from the Ash Meadows Fish Conservation Facility released 19 captive-raised fish into Devils Hole at first, and later added roughly 50 more. By spring surveys recorded 77 fish — a dramatic recovery from the low of 20 and a relief to managers who feared losing the species in its only natural habitat.
The rapid response likely averted extirpation, but it also forfeited a research opportunity: staff did not collect routine genetic samples from the first group of released fish. Without those baseline samples it is now impossible to determine precisely which animals in Devils Hole are descendants of the introduced refuge fish and which are survivors from the original wild population. That gap limits scientists’ ability to trace how the captive fish contribute to future generations and to measure any genetic or evolutionary impacts of the rescue.
Agency officials say the rush to act was driven by fear that federal layoffs and a possible government shutdown would soon strip away staff and resources needed to respond. Faced with the prospect of being unable to monitor the population if they delayed, managers prioritized immediate action over meticulous data collection. They judged that waiting to perform standard fin clips and recovery procedures on the refuge fish could risk losing remaining wild individuals if the population failed in the interim.
Devils Hole is among the smallest known habitats of any vertebrate: a warm cavern pool only a few dozen feet across that stays near 93 degrees Fahrenheit and supports very low levels of nutrients and oxygen. Park and agency teams have counted the pupfish twice each year for decades. After a decline to 35 fish in 2013, agencies established a refuge at Ash Meadows — a 100,000-gallon tank meant to replicate Devils Hole and serve as an emergency backup. Transfers back to the wild were always considered a last resort because captive populations can differ from wild ones and could introduce disease or change the wild gene pool.
Through much of the last decade the wild population remained stable and even climbed: by fall 2024 biologists counted 212 fish. Then distant earthquakes in December 2024 and February 2025 sent powerful ground pulses through Devils Hole that produced mini “desert tsunamis” inside the pool. Those waves scoured a shallow rocky shelf and cleared away the algae the pupfish feed on. Because the quakes struck during winter, when sunlight doesn’t reach the pool, the algae could not regrow and by late February the population had fallen by roughly 90 percent to about 20 fish.
An interagency Incident Command Team — made up of the U.S. Fish and Wildlife Service, the National Park Service and the Nevada Department of Wildlife — used a 2022 strategic plan to weigh emergency options. The team first added supplemental food to the pool, then after about two weeks concluded that introducing refuge fish was necessary. On March 11, 2025, staff netted fish from the refuge and transferred them the same day. They did not perform the standard genetic fin clips because clipping requires antibiotics and recovery time; managers feared that delay could imperil the remaining wild animals. Instead, they attempted an unproven alternative — saving the water each fish had occupied in hopes DNA could later be extracted — but that method has not been validated.
Geneticists say fin-clipping has been done safely on thousands of fish and that sampling a subset of refuge fish likely could have provided needed data without significantly increasing risk. Without those samples, researchers cannot now answer questions about how quickly refuge genetics mix into the wild population or whether larger, refuge-raised fish might outcompete smaller wild fish and reduce genetic diversity. Such reductions in diversity could affect the species’ ability to adapt to future threats.
After the initial emergency, the immediate time pressure eased and the refuge began collecting DNA from all fish moved to Devils Hole. The Incident Command Team is drafting a genetics management plan to guide future decisions. Recent spring counts showed many juveniles and young fish in the pool, indicating successful reproduction and an upward trend in population numbers. Staff report smoother transfers from the refuge into the wild and have observed less stress in fish during later releases.
Managers emphasize the trade-offs of the crisis response: a rescue that likely prevented loss of the species from its only natural home, but one that complicated scientists’ ability to study genetic contributions and long-term evolutionary consequences. The agencies now face the twin tasks of carefully managing genetics as the population recovers and learning lessons from a crisis shaped both by distant earthquakes and by urgent, policy-driven uncertainty at the federal level.