MEPS 527:143-156 (2015)  -  DOI: https://doi.org/10.3354/meps11238

ABSTRACT: To better understand population connectivity of the blue crab Callinectes sapidus and how it may have been affected by the Deepwater Horizon oil spill, we simulated larval dispersal with a biophysical model of the coastal waters from western Louisiana to the Florida panhandle. We investigated connectivity patterns, intra-annual variability, and potential impacts of the Deepwater Horizon oil spill during the spring and summer of 2010. Overall, we found that the Mississippi River delta (MRD) is a barrier to dispersal, and that local retention was high; of the 7.7% of larvae that successfully settled, 37.5% returned to their natal estuary and 28.5% to an adjacent one. We used network metrics to assess the overall diversity of population connectivity and the importance of individual estuaries to maintaining connectivity. The proportion of larvae that successfully settle does not significantly change during the spawning season, but connectivity among estuaries significantly declines. Estuaries near the MRD were most important for maintaining connectivity, likely because they were the primary source of the few larvae that crossed the MRD. These patterns influence the distribution of settlement locations for larvae that were potentially exposed to oil. A total of 38.1% of the simulated larvae were potentially exposed to oil, and these larvae were concentrated on the eastern side of the MRD. For some spawning events, up to 96.3% of the larvae that successfully settled east of the MRD were potentially exposed to oil, which may have substantial implications for population dynamics. These results provide quantitative predictions regarding blue crab connectivity in the northern Gulf of Mexico that can be corroborated with data. The predictions can be applied for disaster management planning and for management of this environmentally and economically important species.

KEY WORDS: Lagrangian particle tracking · Graph-theoretic metric · Shannon index · Vertex degree · Betweenness centrality · Potential connectivity