These polygons delineate areas that are believed to be suitable for shellfish based on the expertise of the Massachusetts Division of Marine Fisheries (MarineFisheries) and local Shellfish Constables, input from commercial fishermen, and information contained in maps and studies of shellfish in Massachusetts. The areas covered include sites where shellfish have been observed since the mid-1970's, but may not currently support any shellfish. Therefore, these maps represent potential habitat areas.

This layer was developed by Marine Fisheries in collaboration with the Massachusetts Office of Coastal Zone Management (CZM) and the National Oceanographic and Atmospheric Administration (NOAA) Coastal Services Center (CSC).  

Areas determined to be suitable for the ten species of shellfish were hand drawn on overlays using either the DMF Designated Shellfish Growing Areas or NOAA Nautical Charts as base maps. The CSC digitized the maps by scanning the overlays and vectorizing the scanned lines. The maps were then checked for accuracy and any missing or incorrectly vectorized lines were corrected. The polygon lines were then snapped directly to the MassGIS Coastline (1:25,000) of 1992 and edited for consistency with the polygon on the base maps.

The layer was then turned into an ArcInfo coverage and was cleaned and built to create polygons. The base maps were then used to code each of the polygons in the layer. When all of the sheets were completed they were checked for errors and quality assurance. The maps were separated into individual layers for each species and saved as shapefiles. MassGIS combined the ten separate shapefiles into one ArcSDE layer, with each polygon coded for the species potentially present in that area. Because some species habitats overlap, overlapping polygons exist within the merged layer.