Rock Scallops

Crassadoma gigantea

Rock Scallops

Crassadoma gigantea
Other Common Names
Giant rock scallop, purple-hinged rock scallop
Other Common Names
Giant rock scallop, purple-hinged rock scallop

At the Aquarium

Rocky Coast

Appearance

The valves, or shells, of this scallop are thick and almost circular. The right valve is cemented to the substrate. The hinge has extensions (or wings) on either side, though these might not always be visible. The fleshy mantle is orange and contains rows of eyes.

Habitat

Nearshore rocky substrates or pier pilings with strong currents on exposed outer coasts from the low intertidal to depths of 300 feet, though usually found at depths between 10-150 feet.

Diet

Filter-feeds on microscopic plankton

Life History

Rock scallops are usually male or female, though rare individuals are both sexes and can produce both eggs and sperm. They reproduce by broadcast spawning. The planktonic larval stages last 2 months. A juvenile swims by clapping its valves together, until it reaches a shell-height of at least 1 inch, at which point it begins the process of finding a spot to settle. Once it finds an ideal spot, it cements itself to the hard substrate using abyssal threads. It remains anchored in its chosen spot for the rest of its life. As the scallop continues to grow, its shape will distort to fit the surface it is attached to.
Grows up to 9.8 inches in diameter with a lifespan of 50 years

IUCN Status

Not Evaluated

Ecosystem & Cultural Importance

Humans eat the large muscle of this scallop, called the adductor muscle, which is what the animal uses to open and close its shell. Native Americans have used rock scallops for food and their shells as pendants, lip plugs, and nose rings. They’ve also used the shells in facial and mask paint, and the scallops were used in totem pole and canoe designs. Due to the large size of its meat and excellent taste, there is much research and interest in creating a commercial aquaculture fishery for these scallops.
These members of the marine food web are eaten by sea otters, sea stars (including ochre stars, giant pink sea stars, and rainbow stars), California spiny lobsters, and fish such as striped surfperch, painted greenlings, blackeye gobies and senoritas.
Other organisms will live on the shells of rock scallops, including barnacles, anemones, boring sponges, tube worms, bryozoans, and coralline algae. In addition, pea crabs will sometimes live inside the mantle cavity of the rock scallop.
Alaska to Baja California, Mexico
Sport Divers (permits required) will harvest rock scallops along rocky, high current areas in Oregon’s nearshore. If you find a scallop shell on the beach with purple on the interior and next to the hinge, this is a rock scallo
This is the heaviest species of scallop in the world.
Sometimes a loud snap can be heard when this scallop shuts its valves.
Rock Scallops are a Strategy Species in the Oregon Conservation Strategy.

Citations & Other Resources