Macedo, Danielle Carter De (2017-05). Population Genetics of the Blue Crab (Callinectes sapidus) in the Gulf of Mexico, Chesapeake Bay, and Western South Atlantic. Master's Thesis.
The blue crab, Callinectes sapidus, is an important species in estuarine habitats, serving as both predator and prey to other species, and plays a pivotal ecological and economic role throughout its range. In recent years, however, its populations have been declining. Declining blue crab populations will negatively affect critically endangered organisms that depend on the blue crab, like Kemp's Ridley sea turtles and whooping cranes, as well as commercially important fish species, such as red drum, Sciaenops ocellatus. Despite its importance, little is known about its genetic population structure, which can be affected by population reductions. Previous research provides conflicting evidence of genetic variation in the blue crab across its range. Some studies have identified significant population structure in blue crabs in the Gulf of Mexico, attributed to seasonality, catastrophic events, and post-larval selection, while others have found genetic homogeneity in the Texas coast, possibly due to gene flow by larval dispersal. The results from previous studies are being used to implement management strategies, despite their limitations. In this study, population structure of the blue crab was assessed throughout the Gulf of Mexico, in the Chesapeake Bay, and southern Brazil using sixteen microsatellite markers. The results show high levels of gene flow for the blue crabs in the United States (GST = 0.005; DST = 0.015), with no genetic differentiation identified by any of the analyses. There is evidence of strong genetic differentiation between the U.S. and Brazil (GST = 0.067; DST = 0.056). No signs of a recent bottleneck were detected in any of the populations. Estimated NE was very high for all populations. This information will aid management decisions for the blue crab and help preserve this important species by improving stock delineations and providing a baseline of genetic diversity.