Montana Field Guide

Golden Mussel was recently detected in California, the first known occurrence of the species in North America (California Department of Fish and Wildlife 2024). Golden mussels were likely introduced to California by a ship traveling from an international port. They are likely to spread throughout the Delta and through the water conveyance systems associated with it. Without containment, golden mussels are likely to spread to other freshwater bodies in California, and to other ports and inland waters of North America and abroad. In waterways where this species is present, heavy encrustations of golden mussels have blocked municipal and industrial water intakes, necessitated ongoing biofouling removal, harmed native species in the ecosystem, increased water clarity due to intense filter feeding, and diminished water quality.