In January 2007, tiny quagga mussels from Europe invaded Lake Mead, Nevada. Within months, they began fouling boat engines, docks, and the water intakes of Hoover Dam. Now quaggas are spreading across the west and Oregon is bracing for a costly invasion that threatens everything from hydropower to salmon recovery. Learn more about the threat posed by this invasive species and the prevention efforts underway to stop their spread to Oregon.