The mediterranean mussel Mytilus galloprovincialis Lmk. in Japan

Mussels (Mytilus sp.) from Sanriku Bay, NE Honshu, Japan were examined using morphological characters and electrophoretically detectable enzyme polymorphisms. Using both sets of criteria, the mussels were identified as M. galloprovincialis, the mediterranean mussel. This confirms an earlier opinion, which was based on morphological criteria alone, that the mediterranean mussel occurs on the mainland coast of Japan. Investigation of some early Japanese literature suggests that mussels did not occur in this area earlier this century, and M. galloprovincialis may have been introduced to the region of Kobe, around 1930–1935. The present‐day distribution of M. edulis and M. galloprovincialis in the Japanese archipelago may be explained by sea‐surface temperatures in the region.