HEIGHT OF ATTACHMENT ON SEAGRASS LEADS TO TRADE-OFF BETWEEN GROWTH AND SURVIVAL IN THE BAY SCALLOP ARGOPECTEN-IRRADIANS

Recent experiments have demonstrated that the canopy of seagrass beds provides a refuge from predation for juvenile bay scallops Argopecten irradians. Elevation off the bottom may also place juvenile scallops attached to grass blades in flow regimes more favorable to growth than if they settled on the bottom. Juvenile scallops (mean shell height 12.3 mm) were attached to seagrass mimics at 0, 5, and 15 cm off the bottom and their survival was followed over three 24 h periods; growth and survival were then monitored after 2, 3, and 9 wk. Survival at the 0 cm elevation was significantly lower than at 15 cm while survival at the 5 cm elevation was not significantly different from either extreme. Scallops grew fastest at 0 cm, significantly slower at 15 cm, and slowest at 5 cm. Selection of attachment locations off the bottom by juvenile scallops incurs the cost of reduced growth and scallops are faced with a trade-off between reducing their risk of predation and maximizing their growth.