Pesky quagga mussels that were first discovered Jan. 6 in Lake Mead's Boulder Basin and later at each end of Lake Mohave and downstream in Lake Havasu were found this week at Willow Beach National Fish Hatchery, wildlife officials said Friday.

Zen Mocarski, spokesman for the Arizona Game and Fish Department office in Kingman, said the invasive, zebra-type mussels were found Thursday in three settling ponds at the hatchery.

The U.S. Fish and Wildlife hatchery where trout and native Colorado River fish are raised is on the Arizona side of Lake Mohave about 10 miles downstream of Hoover Dam.

Mocarski said none of the ponds was being used to house fish when the mussels were discovered.

The quagga mussel is a cousin of the more commonly known zebra mussel. Both species infested the Great Lakes region more than a decade ago after they were transported in ballast water from ships from the Ukraine and eastern Europe.

Colonies of the invasive mussels can clog water supply pipes and ruin marine equipment.

The quagga mussels found Thursday at the Willow Beach hatchery ranged in size up to a half-inch-long, Mocarski said.

Any fish leaving the hatchery in trucks filled with well water will be given a static bath for 30 minutes in a solution of 75 parts per million potassium chloride, enough to kill quaggas and their larvae, he said.

Meanwhile, the National Park Service issued a statement late Friday asking recreational scuba divers to report sightings of suspected quagga or zebra mussels.

The 100th Meridian Initiative, an interagency clearing house devoted to stopping the spread of nuisance aquatic species, has installed a "divers section" on its Web site, www.100thMeridian.org, to report mussel sightings.

"If we receive a quagga report from scuba divers, we can use our limited diving resources to make and assessment of the extent of the infestation," said Kent Turner, chief of resources management at the Lake Mead National Recreation Area.