Bay Scallop, Argopecten irradians, Restoration in the Virginia Coastal Bays: The Role of Predation on Spring Vs Fall Cohort Survival

While the importance o f predation in controlling many natural bivalve populations is well established, it is often overlooked in the restoration strategies for depleted populations. Adult bay scallops {Argopecten irradians concentricus) along the U.S. mid-Atlantic coast spawn multiple times per year, typically once in the early summer and again in the early fall. Larvae generally settle on seagrass leaves to avoid benthic predators, but shift to the sediment surface around 20 mm in size when they become less vulnerable to predation. The objectives o f this study were to 1.) Determine proportional survival o f two distinct size classes o f A. irradians in different seasons related to the two naturally occurring cohorts found in this region, 2.) Determine the identity o f key predators o f A. irradians in the Virginia coastal bays. The goal is to incorporate this information into a restoration strategy for a Virginia seaside lagoon system where A. irradians have been absent since the disappearance o f eelgrass in the 1930s. Tethering experiments, conducted in re-established eelgrass during summer and fall o f 2013 and 2014, o f small (~10 mm SH) and large (~32 mm SH) juvenile A. irradians showed significant differences between the two years, likely due to the differences in the predator community. They also showed much higher predation rates in July than in August or October for both 2013 and 2014. Blue crabs are significant predators o f A. irradians and were present only in 2014, affecting survival, especially o f the large size class. Fish predators, such as pinfish, pigfish, striped burrfish, and sheepshead appear to have controlled the survival o f small juvenile A. irradians. Our results generally show greater survival in the fall, thus perhaps focusing on deploying small A. irradians in the fall would increase survival. However, the large differences in survival between 2013 and 2014 point to the importance o f employing an adaptive restoration approach which incorporates real-time abundances o f predators into restoration activities, allowing for the release o f A. irradians at smaller sizes dependent on the composition o f the predator assemblage