Rare fish species in Nevada desert cavern on the rebound

DEATH VALLEY NATIONAL PARK, Calif. (AP) — The annual fall count of an extremely rare fish species that lives in a single Mojave Desert cavern found the highest number in 19 years, the National Park Service said.

Scientists counted 263 Devils Hole pupfish last month, the highest autumn count since September 2003, the agency said in a statement.

Devils Hole is a deep water-filled cavern in a detached unit of Death Valley National Park located in Nye County, Nevada.

The pupfish live in the upper 80 feet (24.4 meters) of the water column and on a shallow, sun-lit shelf at the cavern’s mouth where they forage and spawn.

The count is conducted by scuba divers and observers on the surface who tally the fish on the shelf.

The National Park Service said the population survey received an unusual assist. The count followed a Sept. 19 magnitude 7.6 earthquake in Mexico that caused water to slosh around in Devils Hole, removing algae, invertebrates and other organic matter from the shelf, making it easier for biologists to see the pupfish.

Researchers were on site at the time of the quake and recorded video of the desert tsunami.

Biologists say that before the 1990s, the pupfish population was around 400 to 500 in the fall, but numbers were particularly low in the last two decades, averaging 90 fish. The all-time low was 35 fish.

The latest count was a 51% increase from last fall’s tally of 174 fish, and biologists noted that all sizes of fish were abundant, they appeared to be in remarkable condition and were active, with many courting and spawning pairs observed.

“Recent high spring and fall counts show the importance of maintaining long-term data as we work to find out what’s changed,” said Kevin Wilson, aquatic ecologist for Death Valley National Park.

The next pupfish count will be done in spring 2023.