Monday October 3, 2022

National Park Service

Agency biologists are excited to report increased numbers of one of the world’s rarest fishes. Scientists counted 263 Devils Hole pupfish, which is the most they’ve observed in 19 years.

This count came on the heels of a magnitude 7.6 earthquake in Mexico that caused 4-foot waves in Devils Hole on Sept 19, 2022. Pupfish are counted using both scuba and surface visual counters. Sloshing waves removed algae, invertebrates, and other organic matter from a shallow shelf that pupfish use to forage and spawn. This made it easier for biologists to see and count pupfish from the surface.  Scientists using scuba also counted pupfish at greater depths. 

Devils Hole pupfish (Cyprinodon diabolis) live in the upper 80 feet of a deep water-filled cavern and sun-lit shallow shelf at the cavern’s entrance, making this the smallest range of any vertebrate species on the planet. Devils Hole is 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 cooperate to manage this critically endangered species.

Population size is estimated by counting fish throughout its habitat, with standard counting protocols. Scientists scuba dive to count fish in the cavern, starting at depths below 100 feet. Simultaneously, other scientists count fish on the shallow shelf at the waters’ surface. The final count includes both surface and underwater fish. The official result, 263 observable pupfish, is the highest autumn count recorded since September 2003. 

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