Pupfish count steady
Divers who surveyed a water-filled limestone cave 90 miles northwest of Las Vegas found that the planet’s only wild population of Devil’s Hole pupfish had not dropped below the lowest estimate of 38 counted a year ago, a U.S. Fish and Wildlife Service official said Monday.
“The population, while small, is holding its own,” Bob Williams, Nevada’s field supervisor for the U.S. Fish and Wildlife Service, said about the Saturday count at Devil’s Hole, a protected part of Death Valley National Park that’s in Nevada near Ash Meadows National Wildlife Refuge.
The count matched last year’s spring count, the lowest on record. But the population held to its cycle of rebounding in the fall to 88, then declining in the winter.
In January biologists dropped food in the hole to augment the diet of the inch-long, neon-blue fish. Williams said, however, that his team of wildlife biologists can’t attribute the 38 thriving fish to the feeding experiment.
“While the number we were hoping would be higher, the difference between ’06 and ’07 is all the things we’ve done,” Williams said.
He was referring to efforts to breed a select number of Devil’s Hole pupfish at Willow Beach National Fish Hatchery on Lake Mohave and at the Point of Rocks refugium near Devil’s Hole at Ash Meadows.
Two adults and a juvenile pupfish have survived a translocation experiment at Point of Rocks and three adults and a juvenile are swimming along with three larvae that hatched from eggs at the hatchery. A fourth egg is about ready to hatch, Williams said.
“I think we’re getting the techniques down where we can have better success at the hatchery,” he said.
Williams said a task force will soon make recommendations to regional wildlife managers on how to increase the captive population at Point of Rocks and increase propagation at Willow Beach.
No pupfish are living in a concrete tank near Hoover Dam that once housed a reserve population until a snail infestation occurred.
Despite efforts to clean the tank, the snail problem persists.
The population once peaked at 553, based on estimates of the counts that have been conducted twice each year for the past few decades.
But the species’ numbers had been in decline in recent years for unknown reasons.
Then the population took a sharp turn for the worse on Sept. 11, 2004, when a flash flood sent a tub of glass fish traps tumbling into the hole. The traps were being used by Southern Oregon University researchers to assess pupfish reproduction.
Death Valley National Park officials did not realize until several days after the flood that some of the unbroken fish traps ended up capturing and killing about one-third of the pupfish population at the time, 80 in all.