Bay Mussel         Mytilus trossulus

The Bay mussel, or sometimes called the Blue mussel, is very common in the protected waters of Puget Sound, but occurs north to Alaska and south to Mexico.  It is characterized by it's relatively small size, averaging around several inches long, although it can grow up to 4 to 6 inches.  It also has a smooth shell, ranging in color from dark blue to brown.  

It used to be called by the scientific name of Mytilus edulis but recent chemical studies have determined that it is a different species.  In addition there is evidence that it is interbreeding with other mussel species introduced into the area.  There are several other species of native mussel, such as the Northern Horsemussel and the California Mussel, that also occur in the area but live in different habitats.

Related to clams, mussels differ by living above the sediment attached to hard substrate.   Many thin tough strings of protein, called byssal threads or commonly the beard,  are used to anchor the shell preventing it from being washed away by waves or currents.  The foot, used by clams for digging, is used by the mussel to attach the byssal threads. They feed by filtering gallons of seawater each day to obtain their food. In turn they are eaten by a range of animals from sea stars to humans.  Spawning occurs in April and May with the larvae living in the plankton for a month or two before settling.