Spatial population dynamics of eastern oyster in the Chesapeake Bay, Maryland

Incorporating spatial information can improve estimates from stock assessment models when there are differences in population processes (e.g., natural mortality) among areas. Population dynamics of the eastern oyster Crassostrea virginica vary spatially within the Chesapeake Bay, Maryland, and our objective was to better characterize oyster population dynamics by estimating changes in natural mortality, fishing mortality, abundance, and recruitment over time and space. We developed statistical stage-structured models for 36 regions and fit the models to fishery dependent and independent data sources. Regional patterns in population dynamics emerged that would have been lost in a spatially aggregated approach. Regions that were closer together tended to have similar patterns in natural mortality, exploitation rates, abundance, and recruitment over time. We were able to estimate time-varying natural mortality because ancillary data on the number of dead individuals were incorporated into the population dynamics model. This approach to estimating time-varying natural mortality may be more widely applicable to species where dead individuals are observed in routine surveys.