Rock Scallop
Crassodoma gigantea

Physical Description

  • Thick, round, ribbed shell with many spines
  • Shells often covered in plant, animal, algae growth
  • Mantle (edge of shell) is bright orange with black eyes running along it
  • Up to 10 inches across


  • From northern Alaska to northern Mexico


  • 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
  • Under rocks and in crevices
  • Depths of 0-252 feet


  • Rock scallops are suspension feeders who filter particulates and plankton out of the water


  • Lobsters, crabs, sea stars, fishes
  • Traditional food of coastal First Nations people

Interesting Facts

  • Rock scallops are the heaviest and 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 up to 20 years! 

Sources:; Macdonald et al. 1991;, UMass; Catalina Island Marine Institute

Photo: Kevin Lee

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