Rock Scallop
Crassodoma gigantea
Physical Description
- Have a thick, round, ribbed shell with many spines.
- Shells often covered in plant, animal, and algae growth.
- Mantle (scallop body seen at edge of shell) is bright orange with black eyes and sensory tentacles running along it.
- Up to 10 inches in diameter as adults.
- Juvenile rock scallops are unattached to a substrate and swim by clapping their valves together and squirting water out the sides of the hinge.
- Permanently attached to hard substrate as adults; they settle and cement themselves at about 1 inch in diameter.
Range
- From northern Alaska to northern Mexico.
Habitat
- Live in intertidal (area of shoreline covered at high tide and uncovered at low tide) and subtidal (below the low-tide line) waters along exposed outer coasts.
- Found under rocks and in crevices.
- Found at depths of 0-252 feet.
Reproduction
- Reproduce by broadcast spawning, releasing sperm and eggs into the water.
- Spawn twice a year in Southern California, once in late spring-early summer, and again in mid-fall.
Diet
- Rock scallops are suspension feeders who filter particulates and plankton out of the water.
Predators
- Lobsters, crabs, sea stars, fishes.
- Traditional food of coastal First Nations people.
Interesting Facts
- Rock scallops are the heaviest and the second-largest scallop species.
- They are sometimes called the purple-hinged rock scallop because the interior of their hinges are purple.
- Unlike all other scallops, rock scallops cement themselves down permanently to a hard surface once they reach maturity (about an inch across).
- These scallops can live for up to 20 years.
Sources: CentralCoastBiodiversity.org; Macdonald et al. 1991; lobsteranywhere.com, UMass; Catalina Island Marine Institute; Oregon Department of Fish and Wildlife; Oregon Coast Aquarium; California Department of Fish and Game
Photo: Kevin Lee