Scientists say they are unable to explain the steady declined in the number of pupfish -- an endangered species that lives only in a Nevada limestone cave.
For the last decade the number of pupfish in Devils Hole, a deep, water-filled cavern about 80 miles northwest of Las Vegas, has dwindled, the Las Vegas Sun reported Thursday.
The population last month was tallied at 84 -- the same as in February.
Jim Deacon, a University of Nevada-Las Vegas biologist, said, "The expected increase this fall did not happen. All through last summer there was egg-laying and babies produced, but not enough to increase the adult population, so we're still at very dangerous levels."
Observers are increasingly worried that whatever they do, the species may be on a slide to extinction, the newspaper said.
"It doesn't look like there was a change in the ecological relationships," Deacon told the Sun. "One easy cop out is to say there is a genetic bottleneck, but I think that's too easy.
"They've been there for 10,000 or 60,000 years, somewhere in that neighborhood, so why would they blink out now?"
Copyright 2005 by United Press International