Integrating Field Data, Individual-Based Models and Climate Forecasts to Predict Blue Crab Landings

Blue crabs are one of the most important commercial fisheries in the southeast, but landings have declined during recent droughts.  Climate forecast models suggest that in the southeast, we can expect our future climate to be wetter, hotter and more variable than in the past, with a net decrease in river flow.  To better understand this relationship between crab abundance and freshwater flow, we conducted a four year field study of blue crab abundance and distribution in the ACE Basin National Estuarine Reserve.  Crab abundance in low flow rivers suffered higher disease and declined in drought years whereas, crabs in high flow rivers suffered lower predation and increased in drought years.  We then constructed a spatially-explicit, individual-based population model and parameterized the model using our field observations.  We used the model to examine how the rate of flow decline and inter-annual variability under future scenarios of climate change might interact to influence crab abundance, commercial landings, and disease prevalence.  Interannual variability in flow had a much larger impact on crab abundances in the near future, while the rate of flow decline determined the persistence of the fishery into the next century.