Devils Hole pupfish at Death Valley National Park/NPS

Wildlife biologists have good news to report about one of the world’s rarest fishes. Scientists recently counted 187 Devils Hole pupfish, which is the most they’ve observed in 15 years.

“We are not out of the woods, but this is a good step in the continued recovery efforts for this fish,” said Kevin Wilson, aquatic ecologist for Death Valley National Park.

For decades, scientists counted about 200 Devils Hole pupfish in the spring and about 450 in the fall. Pupfish numbers have been precariously low in recent years, dropping to 38 pupfish in 2006-2007 and 35 pupfish in 2013.

Counting pupfish at Devils Hole, Death Valley National Park/Brett Seymour

The only natural habitat of Devils Hole pupfish (Cyprinodon diabolis) is the upper 80 feet of a deep, water-filled cavern and sun-lit shallow pool at the cavern’s entrance. Devils Hole is located in a detached unit of Death Valley National Park adjacent to Ash Meadows National Wildlife Refuge in Nye County, Nevada.

U.S. Fish and Wildlife Service, Nevada Department of Wildlife, and National Park Service staff and volunteers worked together on the official fish count, following methods used since 1972. Some scientists donned scuba gear to count fish in the cavern, starting at 100 feet below the surface. Other scientists stayed on the surface to count fish in the shallow pool. The surface and underwater numbers were added together. Researchers conducted multiple counts on September 29 and 30.

The official result, 187 observable pupfish, is the highest count recorded since September 2003. Michael Schwemm, senior fish biologist for the Fish and Wildlife Service, said, “In natural systems it’s important to appreciate that small populations fluctuate in size seasonally and annually, and it is not uncommon to gain or lose 30 fish between counts. Still, our current count far exceeds this margin.”

The scientists were also pleased by how healthy the pupfish looked, and their age range.

“The majority of the fish we counted were juveniles and young adults,” said Brandon Senger, supervising fisheries biologist for Nevada Department of Wildlife. “This population structure is what is really important and we will continue to monitor this closely.”

The next pupfish count will be held in the spring.