Boat launches at all East Bay Municipal Utility District reservoirs will remain closed in an effort to keep invasive golden mussels from infesting the public water supply, the agency said. Golden mussels haven’t been detected in EBMUD’s seven raw water reservoirs, and the boat launch closures announced this past Thursday are a pre-emptive measure to keep them at bay. Last October, the invasive bivalves were discovered in the Sacramento-San Joaquin Delta — the first known occurrence of the species in North America, according to the California Department of Fish and Wildlife.