Secondary dispersal of early juvenile blue crabs within a wind-driven estuary

Abstract

We used a coupled biophysical study to examine the processes underlying secondary dispersal of early juvenile blue crabs (Callinectes sapidus) within Pamlico Sound, North Carolina, a predominately wind-driven estuary. We quantified the spatiotemporal distribution of early juvenile blue crabs in the water column with vertically stratified plankton samples (during day-night cruises during two consecutive years) and used a hydrodynamic numerical simulation model to recreate dispersal trajectories and assess potential transport pathways connecting inlet (eastern) and western sound nursery habitats. Early juvenile blue crabs belonging to the first benthic instar stage (J1) were observed within the water column, indicative of secondary dispersal occurring rapidly following postlarval settlement and metamorphosis to the juvenile stage. Moreover, J1 blue crabs were most abundant in near-bottom waters at night. Particle-tracking dispersal simulations revealed that across-sound blue crab secondary dispersal only resulted from the combined use of flood-tides near the inlets and wind-induced bottom currents within the main body of Pamlico Sound. Thus, our results indicate that behavioral responses to multiple hydrodynamic conditions ultimately influence habitat connectivity, particularly in the northwest region of our study area where a distinct transport pathway was evident. As such, generalizations of recruitment dynamics based on systems with strong tidal signals cannot be used to accurately characterize patterns of estuarine recruitment in predominately wind-driven systems.