R/EH-1a

Description:

Objectives: Recent analyses suggest that freshwater flow may be an important factor that influences blue crab (Callinectes sapidus) recruitment. The objectives of this research are to 1) determine the vertical distribution of blue crab megalopae in relation to physical and chemical conditions to identify mechanisms that influence megalopae transport into Chesapeake and Delaware estuaries, and 2) use this information with monitoring data and numerical models to determine how differences in freshwater flow could affect blue crab recruitment variability. Methodology: We will address these objectives with a targeted field program and numerical/statistical analyses. We propose to carry out two research cruises to identify spatial gradients in vertical distribution of megalopae from off-shore to on-shore in relation to the day-night cycle and physical conditions. Simulations with coupled 3D hydrodynamic and particle-tracking models will be used to determine how megalopae behavior and changes in freshwater flow influence larval transport into estuaries. Statistical analyses of monitoring data will be used to identify how field and numerical modeling results relate to blue crab recruitment variability. Rationale: The blue crab is of preeminent economic importance in the Middle Atlantic region and supports one of the largest inshore fisheries in the states of Delaware, Maryland, and Virginia. Recent analyses suggest that there are significant gaps in our understanding of the mechanisms that control blue crab recruitment and of relevant biophysical coupling between Delaware Bay and Chesapeake Bay. A better understanding of the factors that promote blue crab recruitment variability within and between estuarine systems is critical for improved management of this commercially and recreationally important species.