Modeling larval dispersal and connectivity for Atlantic sea scallop (Placopecten magellanicus) in the Middle Atlantic Bight

Larval Atlantic sea scallops (Placopecten magellanicus) simulations in the Middle Atlantic Bight (MAB) from 2006 to 2012 were performed to investigate annual and inter-annual dispersal and connectivity patterns among stock regions. These simulations used a circulation model based on the Regional Ocean Modeling System (ROMS) and an individual-based larval model (IBM) that included larval behavior. The circulation model used realistic dynamical forcing (e.g., winds, tides, and open ocean boundary conditions), thermo-dynamical fluxes (e.g., solar radiations, sensible and latent heating), and hydrological forcing; the larval IBM included vertical swimming and sinking behaviour, temperature-dependent growth, and settlement. Simulated larvae that reach settlement size and suitable habitat in 45 days are considered 'successful', and two regions are considered 'connected' by larval dispersal when larvae successfully disperse from one region to the other. In general, simulated larval dispersal patterns varied seasonally (28% higher in September and October compared to May and June), among years (2007 through 2009 had 5% lower larval success during August and September compared to other years), and spatially, with larvae released from the northern regions like Long Island acting as a substantive larval source with 14% greater dispersal success and 15% greater connectivity with other regions than those released elsewhere. Over the seven years simulated, the MAB scallop stocks showed high rates of connectivity to regions to the south and more limited and variable connectivity to regions to the north. In species like sea scallops with limited adult mobility, larval dispersal supplies recruits, enables range expansion, and connects populations. Thus, appreciation of dispersal patterns are essential for fishery management of this economically valuable stock.