Observation: I found a single California Mussel near Little Priest Rock in Unalaska, Alaska. While the geographical range of this species is the Aleutian Islands to Baja California, it is rarely seen in Unalaska.
LEO says: The California mussel (Mytilus californianus) , Habitat and Geographic Range — Abundant, often on surf-exposed rocks and pier pilings. Found mainly in upper-middle intertidal zone on outer coast and can be found subtidal and offshore to 24 m (depth). Aleutian Islands, Alaska to southern Baja, California (Morris 1980). (M. Tcheripanoff)