(3) Classifying species into groups based on species 

 guild, susceptibility to each sampling gear, and life 

 history stage. The six species guilds include shrimps 

 and squids, sessile invertebrates, large decapod crus- 

 taceans, shallow water fishes, demersal fishes, and 

 pelagic fishes. The four sampling gear types include 

 bag seine, trawl, beach seine, and gill net. The two life 

 history stages considered for each species include 

 juvenile and adult. The new classifications are treated 

 as separate data sets. For example, it is determined 

 that adult striped mullet are most likely to be sampled 

 by gill net, while juveniles are most susceptible to bag 

 seine. 



(4) Relative abundance values are determined within 

 the guild-specific data sets based on the numbers of 

 each species. Species not collected are scored as "not 

 present"; those up to the 10th percentile are scored as 

 "rare"; from the 10th to the 50th percentile as "com- 

 mon"; from the 50th to the 90th percentile as "abun- 

 dant"; and from the 90th to the 100th as "highly abun- 

 dant". Monthly relative abundance is calculated for 

 individual species within each guild. 



(5) Monthly relative abundance is plotted for each 

 species in each of the five estuarine salinity zones to 

 provide a first-order estimate of relative abundance 

 within the spatial framework. 



(6) The fishery-independent sampling data are com- 

 pared with the ELMR relative abundance estimates in 

 each salinity zone for all months. ELMR relative 

 abundance values are adjusted if the fishery-indepen- 

 dent data are substantially different, i.e., two or more 

 levels of relative abundance. 



(7) Fishery-independent sampling data and ELMR 

 relative abundance values are mapped together by 

 estuarine salinity zone and season using Arclnfo® 

 and/or ArcView® GIS. 



(8) ELMR program staff meet with regional fisheries 

 experts for peer review of draft maps. 



(9) Revisions are finalized based on the experts' re- 

 views. Figure 20 depicts the relative abundance of 

 pinfish in Galveston Bay for the low salinity period. 



Update of Massachusetts ELMR data. In 1997, NOAA 

 initiated an effort to revise and update Environmental 

 Sensitivity Index (ESI) maps for the coastal zone of 

 Massachusetts, and decided to use ELMR data to 

 characterize the distribution and abundance of fishes 

 and invertebrates in estuaries and coastal waters. 

 However, the existing ELMR data for Massachusetts 

 (Mid-Atlantic and North Atlantic regions) had been 

 compiled six years earlier, and did not reflect recent 



trends. Therefore, the existing ELMR data were re- 

 vised and updated using a three-step procedure: 



(1) Developing a seasonal salinity zonation scheme 

 based on estuarine salinity data. 



(2) Revising ELMR information using recent Massa- 

 chusetts Coastal Trawl Survey data. 



(3) Reviewing species maps with local experts. 



The ELMR program derived seasonal salinity zones 

 for Massachusetts from analysis of an estuarine salin- 

 ity data set provided by the Massachusetts Division of 

 Marine Fisheries (MDMF). This data set consisted 

 primarily of surface salinity values taken for MDMF's 

 shellfish water quality monitoring program. Tribu- 

 tary flow gage and precipitation data were acquired to 

 identify representative years. Precipitation, flow data, 

 and monthly salinity averages were evaluated to de- 

 termine which months would be used to represent the 

 high, low, and transitional salinity periods. A contour 

 modelling procedure was applied to the data, with 

 these results: 



(1) Three salinity zones were delineated: 



• Tidal Fresh, to 0.5 ppt. 



• Mixing, 0.5 to 25 ppt. 



• Seawater, greater than 25 ppt. 



(The data did not warrant a five-zone salinity classifi- 

 cation scheme, as was derived for estuarine waters of 

 Louisiana and North Carolina.) 



(2) The analysis identified four "salinity seasons": 



• Low: March through May 



• Increasing: June 



• High: July through September 



• Decreasing: October through February 



(3) The results generally agreed with the original 

 National Estuarine Inventory (NEI) salinity maps 

 (NOAA 1985a). However, several tributaries with 

 seasonal mixing zones were identified. 



(4) Most of the large coastal embayments (Massachu- 

 setts Bay, Cape Cod Bay, Buzzards Bay, Vineyard and 

 Nantucket Sounds) are entirely seawater. 



(5) The majority of mixing zone habitat is within 

 Merrimack River, Plum Island Sound, Taunton River, 

 and the tidal ponds of Martha's Vineyard. 



(6) The majority of tidal fresh habitat is within 

 Merrimack River. 



51 



