Since invasive golden mussels arrived in California a couple of years ago, officials up and down the state have scrambled to come up with solutions to their rapid spread. For months, state and local water agencies tried things like hot water treatments and scraping of docks. … For the most part, efforts to eradicate the newly established species fell short. Instead, statewide water managers leaned on prevention and education, hoping to stem the movement of mussels between bodies of water by imposing boat hull inspections and cleaning protocols at lakes and reservoirs. Recently, though, a water district in Kern County used a copper treatment to effectively kill golden mussels that had established themselves locally. Officials said the move, which worked on full-grown mussels and ones that had not yet attached, represents a tool for water managers in the battle against the destructive species.