Abstract
Many mollusks alter their shell morphology in response to predator exudates or injured conspecifics to lower their predation risk. However, studies have yet to examine whether this predator-avoidance response can be applied under aquaculture scenarios to improve fisheries. We tested whether exposure to predator cues under hatchery conditions can increase the survival of oysters, Crassostrea virginica, planted in the wild. Juvenile oysters grown in a flow-through system were exposed to either caged blue crabs, Callinectes sapidus, or controls of empty cages for four and eight weeks then placed in the field for 30 days. We compared the shell crushing force, shell morphological characteristics, and individual survival of oysters across predator exposure time and treatments. Oysters grown in the hatchery for eight weeks were, on average, 46% larger and almost 2x stronger than oysters grown for four weeks. However, predator exposure also caused a 50% increase in shell strength for both time periods. These differences yielded significantly greater gains in survivorship over time as predator induced oysters nursed for four weeks exhibiting 53% higher survival in the field than unexposed oysters while this survivorship gain jumped to 300% for eight weeks of cue exposure. Our findings demonstrate that predator cues can be an effective means for the industry to increase the operational efficiency of aquaculture and restoration efforts, and may potentially be applied to other bivalve fisheries (e.g. clams, mussels).
