Seasonal and geographical comparisons. To ex- 

 amine general abundance patterns, the numbers of 

 species ranked as "common" or greater were counted 

 by month and by salinity zone for the adult, juvenile, 

 and larval life stages. In Figure 5, the numbers of 

 species were plotted by estuary. In Figure 6, the 

 numbers of species were averaged across estuaries 

 and plotted by month for these life stages. Although 

 these summaries are not statistical analyses, they do 

 provide insights into the seasonal and geographical 

 distribution of selected species in the estuaries: 



• The number of species present appeared to be higher 

 in some estuaries than in others (Figure 5). However, 

 only 58 species were selected for the ELMR North 

 Atlantic region study, and thus the species list was not 

 comprehensive for the region. Some of the selected 

 species occur primarily in the northern Gulf of Maine 

 estuaries (e.g., smooth flounder, ninespine stickle- 

 back), and some occur primarily in the more southern 

 estuaries (e.g., American oyster, scup, daggerblade 

 grass shrimp). In addition, some estuaries and salinity 

 zones (e.g., Wells Harbor, Damariscotta River tidal 

 fresh) were quite small and contained relatively little 

 habitat for several of the selected species. 



• The number of larval species was higher in the 

 southern estuaries (Cape Cod Bay, Boston Bay, Mas- 

 sachusetts Bay, Great Bay) than in the northern ones 

 (Figure 5). This may have resulted, in part, from spawn- 

 ing activity by the more southern species (e.g., Ameri- 

 can oyster, scup, daggerblade grass shrimp) in these 

 systems, and large seawater zones which could ac- 

 commodate more of the marine spawners. 



• The number of species appeared to be lowest in the 

 tidal fresh zone (Figures 5 and 6). However, this could 

 have been partially due to the fact that the selected 

 ELMR species are primarily estuarine, not freshwater. 

 Most of the ELMR species found in fresh water are 

 diadromous, temporarily using the zone as a spawning 

 ground or corridor to other breeding areas. In addition, 

 the lack of systematic faunal surveys in many tidal 

 freshwater zones contribute to this apparent lower 

 diversity. 



• Estuarine utilization by all three life stages was 

 highest in the summer and lowest in the winter, with 

 some notable exceptions (e.g., winter flounder, Atlan- 

 tic herring) (Figure 6). 



• The number of species present as larvae in the mixing 

 and seawater zones was highest in June. The number 

 of species present as adults or juveniles was highest in 

 September and October (Figure 6). 



Data Content and Quality 



Data reliability. An important aspect of the ELMR 

 program, especially since it is based primarily on 

 literature and consultations, is to determine the quality 

 of available data. The quality of available information 

 varied between species, life stage, and estuary, due to 

 differences in gear selectivity, difficulty in identifying 

 larvae, difficulty in sampling various habitats, and the 

 extent of sampling and analysis in particular studies. 

 As a result, spatial and temporal resolution was greater 

 in well-studied estuaries and for well-studied species. 

 For example, a large amount of information was avail- 

 able on the American lobster in the seawater zone 

 because it is highly valued both commercially and 

 recreationally. Conversely, very little is known about 

 smooth flounder in the tidal fresh zone. Similarly, early 

 life history and spawning activity are often poorly 

 documented. Except for a few species, very little data 

 has been generated on specific habitat preferences. 

 This is particularly true for the forage and/or non- 

 commercial fishes and invertebrates. In addition, life 

 history data are lacking or incomplete even for some of 

 the commercially important and pelagic species. Given 

 this situation, an objective of the ELMR program was to 

 describe the quality of available data. Therefore, a 

 deliberate effort was made to assess the data reliability 

 so that the data base could be used appropriately. 

 Estimates of the data reliability for each species and 

 estuary are presented in Table 6 (pp. 1 13-143) of the 

 Data Summary Tables section. Data reliability was 

 classified using the following categories: 



• Highly certain — considerable sampling data avail- 

 able. Distribution, behavior, and preferred habitats well 

 documented within an estuary. 



• Moderately certain — some sampling data available 

 for an estuary. Distribution, preferred habitat, and 

 behavior well documented in similar estuaries. 



• Reasonable inference — little or no sampling data 

 available. Information on distributions, ecology, and 

 preferred habitats documented in similar estuaries. 



Appendices 4, 5, and 6 provide a complete summary 

 of the personal communications and primary refer- 

 ences used so that readers can easily obtain additional 

 information. An opportunity exists to further refine the 

 data presented based upon additional reviews or new 

 research findings. 



Variability in space and time. Species distribution 

 data were organized according to the salinity zone 

 boundaries developed for each estuary in the NEI data 

 atlas- Vol. I and supplement (NOAA 1985). However, 

 these zones can be highly variable due to the many 



