go to: USFWS Gulf of Maine Watershed Habitat Analysis

We used salinity information for modeling habitats for coastal fishes (bluefish, winter flounder) and for the horseshoe crab. The limited information available for this wide geographic area, the dynamic nature of salinity in coastal areas, and the tolerance ranges of most estuarine, freshwater, and marine organisms dictated that the coverage deal with relatively broad but ecologically meaningful salinity zones.

Available wide-scale digital information included annual average salinity conditions characterizing tidal fresh, mixing, and seawater zones of East Coast estuaries, from the NOAA Sea Division. This information was at a 1:250,000 scale. Higher resolution information was overlaid, including 1:24,000 characterizations of fresh, estuarine, and marine zones from aerial photo-interpretation by the USFWS National Wetland Inventory, and by Maine Geological Survey (Coastal Marine Geologic Environments). We also used the Larsen and Doggett (1978) data for Maine estuaries. This verified or improved upstream and downstream limits for the salinity zones in a number of Maine rivers. More detailed data were available from our previous Great Bay, New Hampshire, and Casco Bay, Maine, studies (Banner and Libby 1995, Banner and Hayes 1996), and from coverages developed for habitat suitability modeling for several marine species in Casco Bay and Sheepscot Bay, Maine (Brown et al. 2000).

National Wetland Inventory characterizations of marine ( M*) were used to designate areas as 25 to 35 ppt (saline); areas designated as estuarine (E*) were regarded as 5 to 25 ppt (mixing zone); tidally influenced and interior wetlands were regarded as fresh. These coverages were revised to eliminate impounded or isolated wetlands, and to add or remove river segments, based on Coastal Marine Geologic Environments coverages, salinity surveys, or local knowledge.

The polygon coverages were converted to grids, then combined with salinity grids from earlier works (Casco Bay, Sheepscot Bay, Great Bay), as a Gulf of Maine salinity grid.


Banner, A. and G. Hayes. 1996. Important Habitats of Coastal New Hampshire. Falmouth Maine: U.S. Fish and Wildlife Service Gulf of Maine Project. 77pp.

Banner, A. and J. Libby. 1995. Identification of important habitats in the lower Casco Bay watershed. U. S. Fish and Wildlife Service, Gulf of Maine Project. 75 pp.

Brown, S.K., K.R. Buja, S.H. Jury, M.E. Monaco and A. Banner. 2000. Habitat suitability index models for eight fish and invertebrate species in Casco and Sheepscot Bays, Maine. North American J. Fish. Manage. 20:408-435.

Larsen, P. and L. Doggett. 1978. The Salinity and Temperature Distributions of Selected Maine Estuaries. Bigelow Laboratory Contribution Number 2-76.