Incredibly Rare Fish Species at 19-Year High in Death Valley National Park

by Craig Garrett
Cyprinodon macularius is a rare species of fish in the family Cyprinodontidae and is known by the common name desert pupfish. Listed endangered species in the United States. Presently, the only remaining natural populations of the desert pupfish are locat - stock photo

Death Valley National Park is home to one of the world’s rarest fish, and biologists are thrilled to report that their numbers are increasing. 263 Devils Hole pupfish were counted by scientists. This is the most that researchers have observed in 19 years, the National Park Service confirmed.

This count came just after a magnitude 7.6 earthquake in Mexico caused 4-foot waves in Devils Hole on September 19, 2022. Both scuba and surface visual counts are used to count pupfish. Waterlogging caused algae, invertebrates, and other organic debris to be washed away from a shallow shelf where pupfish feed and reproduce. Scientists could now study and count pupfish from the surface, which made it much easier. Biologists also conducted surveys at greater depths using scuba.

Devils Hole pupfish (Cyprinodon diabolis) dwell in the upper 80 feet of a deep water-filled cave with sun-lit shallow shelf at the cave’s entrance. This makes it one of the planet’s smallest ranges for a species. Devils Hole is a Nevada National Park unit adjacent to Ash Meadows National Wildlife Refuge. The US Fish and Wildlife Service, Nevada Department of Game and Fish, and National Park Service work together to preserve this extremely rare vertebrate species.

The cave fish’s population is estimated by counting the fish throughout their territory, utilizing standard counting methods. Scientists scuba dive to count fish in the cavern, starting at depths of 100 feet or less. At the same time, researchers on the shallow shelf above the water collect data. The final tally includes both surface and aquatic animals. The most recent autumn census revealed a total of 263 observable pupfish. This is greater than any previously recorded figure since September 2003.

The increase of pupfish at Devils Hole National Park bodes well for the species

The pupfish population has declined significantly in the last two decades, from an average of 400-500 fish to only 90. The return of pupfish in large numbers could be an indication of vital changes taking place in the ecosystem. Kevin Wilson, Aquatic Ecologist for Death Valley National Park, manages the resources of Devils Hole National Park. He weighed in on the increase. “[The] recent high spring and fall counts show the importance of maintaining long-term data as we work to find out what’s changed,” Wilson explained.

Brandon Senger, Supervising Fisheries Biologist for the Nevada Department of Wildlife, has been conducting scuba -counts at Devils Hole since 2014. “I have never seen the population this robust before, Denger said. “Fish of all size classes were abundant. We SCUBA-counted more fish on one level than we have in total in previous counts.”

On-site biologists noted that the fish present appeared to be in good condition and much more active than usual. Many pairs of pupfish were seen courting and spawning during the count. The addition of more pupfish to Devils Hole has an influence on the species recovery’s direction and focus. The current count continues a nine-year trend of increasing numbers, which began at the all-time low of 35 fish.