Predation of Sea Scallops, Placopecten magellanicus, by the Rock Crab, Cancer irroratus, and the American Lobster, Homarus americanus

Various predation techniques used by rock crabs, Cancer irroratus, and American lobsters, Homarus americanus, to open sea scallop, Placopecten magellanicus, prey are reported. Adult rock crabs and lobsters successfully fed on sea scallops up to 72 and 76 mm in height, respectively. Juvenile lobsters were capable of preying on scallops whose height exceeded their own carapace length. Daily predation rates on a range of scallop sizes by various sizes of predator were obtained. Given a choice, both rock crabs and lobsters showed distinct and constant preferences for certain size scallops. This preferred prey size increased with predator size. These laboratory studies demonstrated that both rock crabs and lobsters are potential scallop predators.