The mystery of Death Valley’s missing pupfish

 

Updated 3/12/12 3:01 p.m.

The Devil's Hole pupfish is arguably one of the cooler species around. These tiny iridescent blue fish, just a bit over an inch long, live in one place only, a deep pool in the Amargosa Valley of west Nevada, in a place called Ash Meadows, an outpost of California's Death Valley National Park. The pool, which is about 8 feet wide and 35 feet long, appears a clear and light blue where a flat rock shelf runs just below its surface, deepening to dark turquoise where the shelf drops off. No one knows how deep the pool is; divers have gone 435 down and not hit bottom. "I like to think of Devil's Hole, when you're looking at it, as a window into the aquifer," says Kevin Wilson, an ecologist and manager of Death Valley's Devil's Hole program, which is jointly run by the U.S. Fish and Wildlife Service, the Nevada Department of Wildlife, and the National Park Service.

The water body is not what biologists would consider a welcoming habitat. Its average temperature is 93 degrees, and since it is so still, lacking an outlet where moving water mixes with air, it is oxygen deprived, with about one-third as much oxygen as the average desert spring, says Wilson. Scientists have been keeping watch over these pupfish, one of the most imperiled species in the world, since before the Endangered Species Act was passed. One of the first threats was groundwater pumping from the aquifer feeding the hole in the Amargosa Valley; after a long court battle, the government secured senior water rights protecting the pupfish and their pool in 1976. When the ESA was passed in 1973, pupfish were one of the first species listed.

The Devil's Hole is protected by a chain link fence. Visitors to the site can only view the hole from inside a long steel cage, which starts inside the fencing and leads out to a viewing platform over the small canyon holding the pool.

But despite all this protection, in the 1990s, the pupfish population, which is counted each spring and fall and had hovered in the range of 200-500 individuals (there are always fewer in the spring, and more in the fall), began to dwindle. The counts kept getting slowly lower, year after year. Some years they'd bounce back up, but the general trend went down, down, down. And then, in the spring of 2006, biologists on their spring dive counted only 38 pupfish.

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