They are found only on the west coast of North America, and range from Baja California to Alaska. Sea mussels form dense beds, generally in the intertidal zone of exposed rocky shores.
Sea mussels spawn throughout the year, with peaks in activity in the spring and fall.
Fertilization is external, and pelagic larvae may spend 3-5 weeks drifting planktonically before settling to adult habitat. Growth rates are variable, depending on availability of food, intertidal elevation, temperature and mussel density. Sea mussels can grow to approximately 270 mm in length, and may live 50-100 years. Size at maturity is approximately 70 mm in length. Sea mussels are filter feeders, and are in turn preyed upon by sea stars, whelks, crabs, fish, birds and marine mammals.