This handout photograph obtained courtesy of the Oregon Parks and Recreation (OPRD) and released June 7, 2012 shows exotic mussels (Mytilus edulis or M. galloprovicialis) which have been found on a dock that drifted to Agate Beach in Oregon following the March 11, 2011 earthquake and tsunami. US officials ordered Japanese seaweed and barnacles to be stripped Thursday from a tsunami-wrecked dock washed up on an Oregon beach, to guard against "possible invasive species" from Japan.