The goal of our project is to create a predictive population model for Gulf of Mexico blue crabs and to assess the impact of the Deepwater Horizon oil spill on this ecologically and economically important species. The project involves a combination of fieldwork and computer modeling, including the use of a fine-scale spatially-explicit oceanographic model. This project, begun in Nov 2009, was funded last year through an NSF RAPID grant and a small rapidresponse fund from Louisiana SeaGrant. With this funding, we conducted a large-scale sampling study of larval and post-larval crabs across the Northern Gulf of Mexico. Analyses of these samples are revealing important impacts of the oil spill on blue crabs. This information will be incorporated into a spatially-explicit population model in order to investigate the state of the fishery stock and to make recommendations for the management response to the spill. Our project has the potential to develop into a large-scale investigation involving multiple undergraduate, graduate and postdoctoral students and to be an important component of a multiinstitutional research consortium. Funding is requested to repeat the larval and post-larval sampling in 2011 in order to both compare the 2010 findings to a year without a major spill, and to establish a multi-year dataset that can be used to evaluate the status of this key species.