Comparison of cultured and wild sea scallops Placopecten magellanicus, using behavioral responses and morphometric and biochemical indices

As the survival of juvenile scallops released onto the seabed is of critical importance in programs seeking to enhance scallop populations, the basis of the vulnerability of seeded cultured scallops needs to be understood. High mortality rates following seeding operations could reflect weaker predator escape responses by cultured scallops. Thus, we compared behavioral responses as well as morphometric and biochemical measurements of cultured and wild sea scallops Placopecten magellanicus (35 to 45 mm shell height) sampled in August 1999 in the Gulf of St. Lawrence, eastern Canada. Cultured scallops had larger somatic tissues and higher muscle energetic contents than their wild counterparts. This may reflect the more favorable temperatures and better food supply during suspension culture. When faced with the starfish predator Asterias vulgaris, cultured scallops responded with a greater number of claps, longer clapping period and faster recuperation of clapping performance. However, wild scallops had stronger shells and showed more intense escape responses (higher clapping rate) to the starfish. These differences contribute to making cultured scallops more vulnerable to predation by grasping predators (crabs) and asteroids.