By Chessa Lowery

Faculty Mentor: Bradley Lamphere

Abstract

The eastern oyster (Crassostrea virginica) is a commercially important shellfish species with a wide variety of predators in the Chesapeake Bay and Rappahannock river. The cownose ray (Rhinoptera bonasus) is recognized as a major predator of C. virginica, however their impact on C. virginica populations is not well understood. Knowledge on size dependent predation will help us understand the impacts different predators have on eastern oyster populations, while also assist in making educated decisions regarding fishing regulations in the Bay. In this experiment, eastern oysters were raised in predator exclusion cages located at 3 sites in the lower Rappahannock. Eighteen cages, each with 100 oysters, were designed to measure predation by small, medium, and large sized predators. Cage mortality and Growth were measured weekly, with 20 oysters from each cage marked for individual sampling. Greater mortality was observed in partial and open cages compared to closed, with no difference observed between partial and open cages. These results indicate that both medium and large predators in the Chesapeake Bay estuary have a major impact on eastern oyster mortality.