Japanese Oyster Borer    Ceratostoma inornatum



Introduced to this area in the 1920’s from Japan as an stowaway in shipments of the Pacific Oyster, the oyster borer has stayed to become a nuisance for the oyster grower.  It is a small snail up to 2 inches long (this specimen is 1.5 inches).  It feeds on oysters, clams and mussels using its tongue or radula to rasp a hole in the shell and scoop out the meat.


It occurs on muddy or sandy mud beaches in the low intertidal zone.  It’s spread to other locations is limited due to it’s lack of a pelagic larval stage.  Therefore movement of oysters between different areas is restricted unless they have been carefully cleaned.


It has a native cousin called the Leafy Hornmouth which is larger with a frill-like shelf around the opening of the shell.  It feeds on clams and barnacles.