OVERVIEW

The Shellfish Suitability Areas layer comprises polygons representing habitats suitable for ten species of shellfish along the coast of Massachusetts. The ten species are:

American Oyster Bay Scallop Blue Mussel European Oyster Ocean Quahog Quahog Razor Clam Sea Scallop Soft-shelled Clam Surf Clam

The polygons delineate areas that are believed to be suitable for shellfish based on the expertise of the Massachusetts Division of Marine Fisheries (DMF), the opinion of local Massachusetts Shellfish Constables, and information contained in maps and studies of shellfish in Massachusetts. The areas covered include sites where shellfish have historically been sighted, but may not currently support any shellfish. The shellfish suitability areas were not verified in the field and the boundaries were not surveyed. For these reasons, the areas should be used only as guides to the approximate locations of potential habitats.

The layer is stored in ArcSDE as SHELLFISHSUIT_POLY.

This layer was developed by DMF 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 1:25,000 shoreline 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. Printed maps of the problem areas with the data were sent to the DMF for correction. The corrected information was then returned to the CSC contractors and the appropriate corrections were made. The maps were separated into individual layers for each species and saved as shapefiles. The corrections were returned to the DMF for a final check and minor corrections were incorporated by CZM.

MassGIS combined the ten separate shapefiles into one ArcSDE layer, with each polygon coded for the species potentially present in that area. Because of the merge of the ten layers, overlapping polygons exist in many areas.

The polygon attribute table contains the HABITAT field, coded as follows for the species potentially present in the polygon:

AO		American Oyster
BS		Bay Scallop
BM		Blue Mussel
EO		European Oyster
OQ		Ocean Quahog
Q		Quahog
RC		Razor Clam
SS		Sea Scallop
SSC		Soft-shelled Clam
SC		Surf Clam

The units of the SHAPE.AREA and SHAPE.LENGTH fields are square meters and meters, respectively.

MAINTENANCE

CZM will send any updates to MassGIS for distribution.

Last Updated 6/23/2004
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