The population of Devils Hole pupfish at Death Valley National Park is trying to rebound from a crash/NPS file
A year after surging to a 25-year population high, the number of endangered Devils Hole pupfish at Death Valley National Park has crashed as a result of two recent earthquakes, according to the National Park Service. However, biologists say the population is on the road to recovery.
During a semiannual survey this spring, biologists from the National Park Service (NPS), U.S. Fish and Wildlife Service (USFWS), and the Nevada Department of Wildlife counted only 38 fish in the deep limestone cavern in Death Valley National Park where they live. In contrast, the official spring count one year earlier recorded 191 fish.
Two earthquakes — one in December and the other in February — triggered waves in Devils Hole’s normally still waters that moved algae, organic material, and fish eggs off a shallow shelf at the cavern’s entrance that provides critical food and spawning habitat for the fish.
Biologists consulted the 2022 Devils Hole Pupfish Strategic Plan, which includes plans on what to do in this situation, and for the first time added captive-raised fish — 19 of them — to the wild population. They also used data from the captive Devils Hole pupfish population at the USFWS Ash Meadows Fish Conservation Facility and the NPS Devils Hole monitoring program to decide how to supplement the fish’s diet until algae can regrow.
“I’m proud of the work of this interagency team to monitor and protect the Devils Hole pupfish,” said Death Valley Superintendent Mike Reynolds. “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.”
Biologists have been counting Devils Hole pupfish nearly every spring and fall since 1972. The team splits up to count fish simultaneously from the surface and by SCUBA diving into the cavern.
During the spring surveys, more than 200 fish were counted up until the mid 1990s. In the early 2000s, an average of 90 fish were counted each spring. The number suddenly declined to 35 fish in 2013.
Michael Schwemm, senior fish biologist for USFWS, notes that swings in population numbers are characteristic of both the species and pupfish in general.
“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,” Schwemm said.
The team of biologists had prepared for a potential population decline for years. Pupfish eggs from Devils Hole have been collected regularly to establish the captive population at the Ash Meadows Fish Conservation Facility. The purposes of this population are to ensure that species does not become extinct and to serve as a source of fish for Devils Hole should that become necessary.
Biologists are optimistic about the future of Devils Hole pupfish because spawning behavior, viable eggs, and larval fish are at normal-to-high levels during the current spring breeding season. Ecosystem monitoring suggests that habitat conditions are improving, and most importantly, natural food sources are recovering as sunlight returns with spring.
“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.”
The next pupfish count will occur in the fall of 2025.
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