The zebra mussel, a small freshwater mollusk native to the Caspian and Black seas, has infested rivers in the eastern United States and now threatens to ride the Lewis and Clark Trail into western streams. Federal agencies are urging all boaters to examine their craft for the prolific pests and report sitings immediately on a hotline. The Bonneville Power Administration (BPA) is distributing brochures and providing the hotline so that vigilant boaters and marine operators can report sightings of zebra mussels or any aquatic nuisance species in 17 western states. The number is: (800) 437-2744. The telephone is staffed 24 hours a day, seven days a week. Agencies on an aquatic nuisance task force are concerned that boats following the Lewis and Clark Trail will be traveling from Midwestern rivers where the mussels already live. Without careful inspection, these boats could easily bring the mussels to the West and the Columbia River Basin. "I can't overemphasize the threat posed by these creatures," said Andy Thoms, BPA biologist and aquatic nuisance species coordinator. "They are right out of a bad horror movie - they multiply like crazy, they are difficult to kill and they eat voraciously. They consume the microscopic base of the food chain and can upset the entire ecology of a lake or stream. They'll attach themselves to almost anything that will hold still, including other shellfish." Zebra mussels range in size from microscopic to almost two inches and are identified by their alternating dark and light stripes. Thoms said the mussels can clog water intakes and encrust boat hulls and almost any surface. They encounter no significant predators in Northwest waters. It turns out most of the mussels' natural enemies would also be undesirable in the region. Prompt identification of invading zebra mussels, followed by pre-emptive efforts to eradicate them before new infestations occur, is the key to success, added Thoms. The hulls, engines and bilges of boats trailered westward are the most likely transport for the mussels. Boaters are urged to thoroughly wash down their craft and drain bilges, live wells, bait buckets and coolers before launching in western waters. Since their introduction to the Great Lakes in 1986, zebra mussels have spread to waterways in at least 20 states and two Canadian provinces. In a nationwide campaign called "The 100th Meridian Initiative," the line against them is being drawn at the 100th degree longitude passing through the U.S. midsection from Texas through the Dakotas and the Canadian province of Manitoba. Few of the mussels have been sighted in the West and the effort is to keep it that way. The nationwide partnership includes state and federal agencies, private industries and user groups. Federal and state agencies will distribute 200,000 brochures at sites frequented by pleasure boaters. "We want boaters to inspect their boats and their gear every time they go out. And we want everyone to know that no matter where they are in the Pacific Northwest, if they see a zebra mussel, call and report it," said Thoms. The Western Regional Panel of the Aquatic Nuisance Species Tasks Force comprises the U.S. Army Corps of Engineers, Pacific States Marine Fisheries Commission, Portland State University, Oregon Sea Grant, Columbia River Inter-Tribal Fish Commission, Idaho Department of Fish and Game, Idaho Invasive Species Council, Oregon Invasive Species Council, Oregon State University, U.S. Fish and Wildlife Service, U.S. Coast Guard, Washington Department of Fish and Wildlife, and Montana Fish and Game.