A concrete tank near Hoover Dam that held some of the few remaining Devil's Hole pupfish became infested with invasive snails, prompting wildlife experts in August to remove all of the adult fish to other facilities, the U.S. Fish and Wildlife Service said Thursday.

The rare desert fish were captured and taken to Mandalay Bay, the Willow Beach fish hatchery on Lake Mohave and a temporary holding facility near the dam.

The problem was mentioned in a statement announcing that a panel of scientists and government wildlife managers "are hopeful" that a plan developed last week in Las Vegas "will reverse the decline of one of the most imperiled desert fish species in North America."

Native only to Nevada, the Devil's Hole pupfish was listed as an endangered species in 1967.

In April, about 19 months after a mishap involving fish traps killed about one-third of the population at Devil's Hole, wildlife officials tallied 67 in existence: 38 at the hole, a water-filled, limestone cave 90 miles northwest of Las Vegas, and 29 at the Hoover Dam tank.

Bob Williams, Nevada's field supervisor for the Fish and Wildlife Service, said a decision putting pupfish back in the Hoover Dam refugium and one at Point of Rocks in Ash Meadows National Wildlife Refuge will be made at the end of September based on a count of the Devil's Hole population.

Both locations were affected by the non-native snails, and how the snails or their eggs were transported to the warm, spring-fed pupfish preserves remains a mystery.

"We're not really sure," Williams said. "It could have come on nets."

Efforts were made to eradicate snails from Point of Rocks and the Hoover Dam site in late July and early August, respectively.

"We've cleaned them out. All the snails have been removed," Williams said by phone Thursday.

Regional managers and biologists from the Fish and Wildlife Service, the National Park Service and the Nevada Department of Wildlife huddled last week to evaluate the risks and benefits of options to prevent the Devil's Hole pupfish population from spiraling further toward extinction.

The panel approved actions to stabilize and recover the pupfish, including consolidating all but two male pupfish that exist outside of Devil's Hole at the Willow Beach hatchery, where biologists will artificially propagate and rear pupfish.

A pair of male pupfish will be kept at the Shark Reef at Mandalay Bay, where biologists will experiment with reproduction techniques using hybridized female pupfish.

Williams said if the September count at Devil's Hole indicates the population is recovering to between 50 or 100 fish, then some of those could be transplanted for reserve populations at Hoover Dam and Point of Rocks.

If the numbers at Devil's Hole are low, Williams said a decision would have to be made on possibly introducing artificially propagated pupfish to increase the population at Devil's Hole.