California Mussel

Mytilus californianus





California mussels (Mytilus californianus) are commonly found in large groups, covering rocks or other hard substrates (3). M. californianus have a thick oval shaped shell ending in a sharp point at its anterior end (3). They are characterized by their radial ribs, indicating age, and by their dark blue-black exterior, with a blue-gray interior (3). Growing up to 12.7 cm long they attach themselves to hard substrate via byssal threads which are extremely strong relative to their size (2).  Life in the intertidal zone means periodic tidal inundation of seawater and periods during which organisms are exposed directly to the air. These extremes limit the habitat of M. californianus; with predation and spatial competition providing the lower limit and the lack of food and high temperatures serving as the upper limit (1). Like most bivalves, M. californianus are filter feeders eating detritus and plankton (2). They are an important food source for purple sea stars (Pisaster ochraceus) (3).

(1) Bayne, B. L., Bayne, C. J., Carefoot, T. C., & Thompson, R. J. (1976). The physiological ecology of Mytilus californianus Conrad. Oecologia, 22(3), 211-228. doi:10.1007/bf00344793

(2) California mussel. (n.d.). Retrieved January 30, 2018, from

(3) Cowles, D. (2002). Mytilus californianus (Conrad, 1837).

Photograph ©2008 Gary McDonald