Tuesday, June 7, 2005 | 11:19 a.m.
Scientists' efforts last year to understand an endangered fish sheltered in one unique desert location tragically pushed the Devils Hole pupfish closer to extinction, officials said Monday.
Approximately 80 of the inch-long silvery fish died in traps late last summer after flash floods unexpectedly pushed scientific equipment into Devils Hole, the vertical cave filled with warm water that is home to the species. National Park Service and U.S. Fish and Wildlife Service scientists said the total killed could be a third or more of the adult fish left alive in the wild.
Scientists estimate that at any one time, the fluctuating population of Devils Hole pupfish might number a few hundred, all in the limestone cavern about 90 miles northwest of Las Vegas outside of Death Valley.
"It was a very tragic occurrence, one that we never thought would happen," said Linda Greene, chief of resource management for Death Valley National Park. The Park Service has jurisdiction over Devils Hole, a feature inside the Ash Meadows National Wildlife Refuge.
The floods occurred Sept. 11 near the end of a summer of flash floods throughout the desert area that includes Devils Hole, Ash Meadows and Death Valley. Greene said traps that were designed to count the young fish larva were chained to the top of the hole.
The flooding dislodged the traps and pushed them into the Devils Hole, where they instead trapped adult pupfish. The scientific equipment was used for research into the endangered fish and it was hoped the work would have contributed to understanding the species as part of the federal government's ongoing effort to preserve the fish.
"The irony was not lost on us," Greene said.
A combination of natural and man-made threats in the past year has pushed the Devils Hole pupfish closer to extinction.
Last summer a 1,670-acre wildland fire, sparked by lightning, threatened Devils Hole. The area is a desert oasis filled with 25 endemic species of plants, snails, aquatic animals and fish, including four endangered fish species, among them the Devils Hole pupfish.
"It is the highest concentration of unique endemic species anywhere in North America, north of Mexico," said Jim Deacon, UNLV emeritus biology professor. Deacon is an expert on Ash Meadows and the Devils Hole pupfish.
The Devils Hole pupfish population fluctuates over time in the mound of volcanic rock in which Devils Hole is situated. The hole fills with debris from late-summer flash floods. The fish spawn in the spring on a shelf in the lake after the sediment is reduced.
"The shelf acts like a conveyor belt," Deacon said, explaining that normally the sediments tumble off the shelf after small earthquakes in the area, leaving a thin layer of nutrient-rich muck that allows for the fish to lay eggs.
But the floods last fall helped build up such a thick sediment layer that the fish couldn't spawn.
Deacon said only 180 Devils Hole pupfish were counted in 2003. When the number of adult fish drops below 100 animals, scientists consider the possibility that the pupfish may not survive.
"We're still holding our breath a little bit," Deacon said of efforts to bring the species back from the brink.
Grant Webber, a biologist with the U.S. Fish and Wildlife Service, said the lesson learned is to keep any kind of instruments, equipment or other man-made items within or near the lip of Devils Hole.
"You lose that many fish, and of course it's a big hit to the population," Webber said. "Now what we know is that we don't store anything down there."
Webber and Linda Manning, Park Service wildlife technician, said the agencies are involved in ongoing efforts to restore the population.
"It's something we've got to deal with. It happened," Manning said.
She said the dead pupfish were not discovered until Sept. 19, more than a week after the original flooding. The Park Service at the time was trying to deal with widespread flooding that killed one person, destroyed roads and affected other parts of the Death Valley and national wildlife complex in Nevada and California.
The traps that killed the dozens of pupfish in the Sept. 11 flooding are no longer being used, Manning said.
Other changes include the removal of metal "framing" near the top of Devils Hole that scientists worry might have altered the flow of debris into the site during the floods. That could have affected the dispersal of material that would have provided habitat for pupfish eggs and larva.
Manning said the Park Service scientists are using a new technique for counting immature pupfish that they believe will have less impact on the species, and the diver teams that used to go down in the hole to count the fish are being kept out, at least for now.
She said all the changes may help the species survive, but the long term prognosis is not good.
"This was a big blow," Manning said, referring to the Sept. 11 incident, "but we have a 10-year decline already in this population. We haven't been able to determine the cause of that drop. We still have that decline and we were still heading down that route."
She said ongoing monitoring, including an effort tonight to gauge the spring spawning, should give some indication of how well the population is holding on.
Webber, with Fish and Wildlife, noted that a population of about 200 of the fish live on outside of Devils Hole as an insurance policy against disaster at the site. If something happened to the pupfish in Devils Hole, the "refuge population" could be used to re-populate the site.
"It's important to emphasize the good thing we're trying to do from this," Webber said. "It's definitely a tragedy, but we're hopeful that the population can bounce back."
Deacon and others learned about the incident that killed the adult fish in a workshop on Devils Hole in Death Valley National Park in mid-May.
Scientists and conservationists have been fighting for the pupfish for decades. In the mid-20th century, the springs forming Ash Meadows watered farms that grew melons, fruit and nut trees and cotton fields. Farmers pumping ground water onto those fertile fields visibly lowered the water level in Devils Hole.
The Devils Hole pupfish was given endangered species status and, after a long court battle in the 1970s, the water it needs to survive. Deacon was one of the scientists who supplied the research that ensured a perpetual water supply to the pupfish.
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