2.1 Study Area Description: Shellfish Waters in North Carolina, USA
The study area spanned all marine and estuarine waters in coastal North Carolina, which are subdivided into shellfish growing areas (SGAs) (Figure 1a,b). SGAs are subdivisions of waterways used to support shellfish harvest through delineating administrative boundaries for regulatory purposes. SGAs spatially cover North Carolina’s shoreline from Currituck Sound in the north to Brunswick County in the south. These SGAs are named with alphabetic letters (e.g. “A”, “B”, etc.; Figure 1b), and further categorized through a letter-number system (ex. “A01”). There are 9 SGA letter groups along North Carolina’s coast and these groups of SGAs have similar ecological features and approximately correspond to County jurisdictions. This study excludes the northernmost SGA (“I”) due to the lack of open shellfish growing areas and discontinuous water quality data. SGAs vary in environmental and managerial conditions across the NC coast. These variations manifest as differences in estuarine type which can be defined using physical measures of area, depth, volume, freshwater flow, and salinity within the estuary (Engle et al., 2007).
SGAs can contain multiple classifications including approved, conditionally approved, restricted, and prohibited areas. Of the 9,208 km2 of shellfish waters, 5,910 km2(64.18%) are approved or conditionally approved. Observations collected through routine monitoring programs are used to help establish the classifications within SGAs. The NCDMF Shellfish Sanitation and Recreational Water Quality Section has jurisdiction over the classification of coastal waters for shellfish harvest, and also regulates closures and openings of conditionally approved SGAs. A majority of the NCDMF sampling stations included in this analysis are within the approved and conditionally managed SGAs (Figure 1a).