Mytilus trossulus (Bay mussel)
2005 Mary Jo Adams
common mussel grows to about 4 ½ inches in length, has a
smooth shell, and is black, blue-black, or brown in color.
Often found in large aggregations, it attaches itself to rocks,
pilings, and other objects by means of byssal threads. Look
for this mussel along shorelines where the water is relatively calm.
Other common names for Mytilus trossulus are blue
mussel, foolish mussel, and edible mussel.
is generally easy to distinguish this mussel from the California
mussel ( Mytilus californianus ), which grows considerably
larger, has coarse ribbing, and lives along the higher energy shorelines
of the outer coast.
Two other mussel species have been introduced
to the Puget Sound area that are not as easy to differentiate from
Mytilus trossulus . Those species are Mytilus
edulis and Mytilus galloprovincialis . In addition
to having very similar appearances with each other and M. trossulus
, they are believed to have hybridized making identification
from external appearance a daunting challenge and creating considerable
This page was created by Mary Jo Adams on 1/23/06.