Seasonal and Inter-annual Variability in Modeled Larval Dispersal and Population Connectivity of Blue Crabs (Callinectes sapidus) in the Northern Gulf of Mexico

Larval dispersal trajectories and their resulting population connectivity patterns are known to be key drivers of population dynamics for many marine organisms. However, few studies to date have examined the temporal variability in population connectivity. Here, we model the larval dispersal and population connectivity of blue crabs in the northern Gulf of Mexico from 2003-2012 and use network analyses to understand how they vary over seasonal and inter-annual scales. We found that in all years, the Mississippi River Delta is a barrier to dispersal. Few larvae cross it and settle successfully. In some years (2004, 2007, 2008, and 2009), 1-2 locations (Adams Bay and Chandeleur Sound) had high (> 0.3) betweenness centrality. These locations are likely to be important for maintaining population connectivity in the region, since more than 30% of larval pathways are predicted to pass through them. Connectivity matrices suggest that some estuaries have consistently high larval retention rates. These include West Cote Blanche Bay, Chandeleur Sound, and, in some years, Pensacola Bay and Atchafalaya Bay. Within the spawning season, we observe a decline in average vertex degree and average source strength in every year. This suggests that seasonal declines in the strength of along-shore currents produce consistent reductions in population connectivity through the spawning season.