The California Mussel (Mytilus californianus) is an edible mussel and a marine bivalve mollusk. They are endemic to the west coast of North America, as they occur from northern Mexico to the Aleutian Islands of Alaska. They like high salinity, low sediment conditions on rocky coasts. California Mussels are often found clustered together in large aggregations. Their shells are thick and the coloration is blue with a heavy brown periostracum. The beaks of the shell are often eroded, and the inner surface is blue and lightly pearly. The flesh of the mussel is orange.