FERTILIZATION SUCCESS IN THE EASTERN OYSTER Crassostrea virginica and HYDRODYNAMIC INFLUENCES OF OYSTER SHELL ON LARVAL RETENTION

Abstract

Natural populations of the eastern oyster, Crassostrea virginica typically form dense, vertically-oriented shell assemblages comprised of rough, irregular surfaces which likely influence local water flow, affecting the transit of particles, including gametes and larvae, over them. Since oysters reproduce externally, dense assemblages of simultaneously spawning oysters may maximize gamete interactions before dilution occurs. In the water column, developing larvae may be transported both passively (with large-scale water flow) and/or actively (due to vertical swimming). Once near the bed, larvae may become entrained in interstitial shell spaces among oysters or oyster shells, further increasing the likelihood of settling within an oyster community. Experiments conducted in this thesis showed fertilization success sharply decreased with increasing distance between introduced gametes in tanks without flow. In addition, more larvae were retained on flume beds covered with shell clumps than those without. Additional flume experiments suggested shell density and shell orientation significantly influenced larval retention.