Modeling the Relationship Between Proximity to Urbanization and Shrimp Density Using a Spatially-Explicit Model. B. R. Gray, School of Public Health and Baruch Institute, University of South Carolina, Columbia, SC; J. W. Daugomah, National Ocean Service, NOAA, Charleston, SC; D. E. Porter, School of Public Health and Baruch Institute, University of South Carolina, Columbia, SC; B. Jones, Baruch Institute, University of South Carolina, Columbia, SC; T. C. Siewicki and M. H. Fulton, National Ocean Service, NOAA, Charleston, SC; and J. W. Drane, School of Public Health
Rapid development adjacent to southeastern estuaries has spurred interest in estimating urbanization effects on estuarine populations. Unfortunately, frequent autocorrelation in field collected data complicates the estimation of anthropogenic influences on natural populations. We estimated the influence of distance from urbanization on the density of adult grass shrimp (Palaemonetes pugio) in a small, moderatelyimpacted estuary in South Carolina using land use and land cover data and spatially-explicit linear models. The influence of distance from urbanization was primarily at distances less than 400 m, but was significantly modified by proximity to a relatively undeveloped section of the estuary. The urbanization effect was best explained by proximity to either docks or bulkheads, and then by wetland area. Autocorrelation between observations appeared substantial when observations were separated by less than 100 m but appeared effectively zero when observations were separated by more than a few hundred meters. Eliminating spatial components from the model produced a significantly poorer fit but greater apparent confidence in most parameter estimates. Removing spatial structure also produced different estimates of urbanization effects on shrimp density and, as a result, different expected densities at all urbanization distances.
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