Recent studies have shown that the tidal-, wind- and buoyancy-driven surface currents govern the transport of blue crab (Callinectes sapidus) larvae within the coastal ocean and estuaries. Here, we develop a model of larval transport within Delaware Bay and the adjoining coastal ocean using a particle advection scheme coupled to a previously validated physical circulation model which includes realistic tidal forcing, bottom bathymetry, wind stress and river discharge. The coupled model is then used to quantify the effects of several mechanisms on larval transport and recruitment in this region and hindcast actual larval settlement for a four-year period. The model is run for the years 1989–1992 and compared with observations of larval settlement collected in the Broadkill River, a small tributary to Delaware Bay. It is able to reproduce all of the major observed recruitment events in 1990–1992, suggesting that larval recruitment is primarily driven by the physical mechanisms included in the model. Analysis of the modeled particle trajectories and the settlement data reveals that wind stress is the dominant mechanism in the determination of the timing of the settlement events, while horizontal diffusion and mortality determine the magnitude of the events. The model fails to agree with observations in 1989, indicating that small-scale physical events as well as larval behavior not reproduced in the numerical model can be important in larval settlement.
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