California mussel

Description:

The shells are blue with some brown streaky bands. The beaks of the shell are often eroded. The shell has coarse radial ribbing and irregular growth lines on the outer surface. The inner surface of the shell is blue and faintly pearly.

Habitat:

Spotted on large rocks with barnacles at the North jetty. The tide was out just enough to expose them.

Notes:

The California mussel prefers the high salinity, low sediment conditions found on open rocky coasts. However, they do not colonize bare rock easily, instead preferring the shelter of pre-existing mussels and their biological filaments. Mussels attach themselves to the hard surfaces using their thread-like byssus. Given the right circumstances, California mussels can grow up to 200 mm (8 inches) in length and may live for more than 20 years. However, mortality in intertidal open coastal environments is often high, resulting from battering from driftwood and other debris, wave pounding, predation, desiccation, and disease. Predators of California mussels include the Pisaster starfish. Their most common food is Phytoplankton.