Giant Rock Scallop

Giant Rock Scallop (Crassedoma giganteum) as seen in our Rocky Shores exhibit.

Giant Rock Scallops have coarsely ribbed shells called valves. The upper valve is usually scallop-shaped but the lower valve takes the shape of the substrate to which it's attached. The thick, heavy valves are brownish on the outside and often riddled with tiny holes. Inside, they're pearly white with a dark purple blotch on the central part of the hinge. The scallop itself is orange with numerous blue eyes and sensory tentacles around the margin. Juvenile Giant Rock Scallops are unattached and swim by clapping their valves together repeatedly and spurting jets of water outward on either side of the hinge. After attaining a diameter of about 1 in. (2.5 cm), the scallop cements its right valve to the rocks and thereafter grows and lives as an attached or sessile organism. Like other bivalves, Giant Rock Scallops filter plankton and tiny organic particles from seawater.

Range & Habitat

Giant rock scallops are common from the Queen Charlotte Islands, British Columbia to Baja California. They live in rock crevices along exposed outer coast, underneath floats and on pilings in bays from the low intertidal zone to subtidal depths of 164 ft. (50 m).

Conservation Status