A population boom has taken the spring count of rare Devils Hole pupfish in Death Valley National Park to a 22-year high of 175, according to the park.
The high number also comes from the 50th annual count of pupfish using SCUBA, dated April 6, 1972.
Devils Hole pupfish (Cyprinodon diabolis) live within the upper 80 feet of a cavern filled with deep water and a sunlit shallow pool at the entrance to the cave, making them the smallest range of any vertebrate species in the planet. Devils Hole is an isolated unit of Death Valley National Park, adjacent to Ash Meadows National Wildlife Refuge in Nye County, Nevada. Staff from the US Fish and Wildlife Service, Nevada Department of Wildlife, and National Park Service are cooperating to manage this critically endangered species.
Population size is estimated by counting fish throughout their habitat, using standard counting protocols. Scientists dive to count fish in the cavern, starting at depths less than 100 feet. Simultaneously, other scientists count the fish on the shallow shelf at the surface of the waters. The final tally includes both surface and underwater fish.
Before the 1990s, the population was regularly around 200 pupfish in the spring. However, pupfish numbers have been particularly low over the past two decades, averaging just 90 fish.
A return to higher numbers of pupfish at this time of year could signal significant changes in the ecosystem. Kevin Wilson, aquatic ecologist for the national park, manages Devils Hole’s resources, and says “changes like these underscore the importance of maintaining long-term data while we work to find out what has changed.”
Having more pupfish in Devils Hole affects the direction and focus of species recovery. This week’s tally continues an overall springtime increase over the past nine years from an all-time low of 35 fish. Michael Schwemm, senior fish biologist for the US Fish and Wildlife Service, said “it’s exciting to see this change because if it persists, it opens up more opportunities to study and explore new options for management”.
The next pupfish count will take place next fall.