Data Content and Quality 



Data reliability. An important aspect of the ELMR 

 program, especially since it is based primarily on data 

 sets, published literature, and consultations, is to de- 

 termine the quality of available data. The quality of 

 available information varied between species, life 

 stage, and estuary, due to differences in gear selectiv- 

 ity, difficulty in identifying larvae, difficulty in sam- 

 pling various habitats, and the extent of sampling and 

 analysis in particular studies. As a result, spatial and 

 temporal resolution was greater in well studied estu- 

 aries and for well studied species. Similarly, the early 

 life history stages and spawning activity are often not 

 as well documented as the juvenile and adult stages. 

 Except for a few species, very little data has been 

 generated on specific habitat affinities. This is par- 

 ticularly true for the forage and/or noncommercial 

 fishes and invertebrates. In addition, life history data 

 are lacking or incomplete even for some of the com- 

 mercially 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 reliabil- 

 ity so that the data base could be used appropriately. 

 Data reliability was classified using the following 

 categories: 



• Highly certain — considerable sampling data avail- 

 able. Distribution, behavior, and preferred habi- 

 tats well documented within an estuary. 



• Moderately certain — some sampling data avail- 

 able for an estuary. Distribution, preferred habi- 

 tat, 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 es- 

 tuaries. 



Estimates of the data reliability for each species and 

 estuary are presented in Data Reliability tables within 

 each regional report. Each regional summary report 

 also provides lists of personal communications and 

 primary references used so that readers can easily 

 obtain additional information. An opportunity exists 

 to further refine the data presented based upon addi- 

 tional 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 1985a). 

 However, these zones can be highly variable due to 

 the many interactive factors that affect salinity, such 



as freshwater inflow, wind and tides. To compile 

 information on species distribution according to these 

 zones, it is assumed that if a particular salinity zone 

 expands or contracts, the distribution of a mobile 

 species in that zone will correspond to the shift. For 

 example, if increased freshwater inflow enlarges the 

 tidal fresh zone, the distribution of a species confined 

 to that zone increases to include the new area. If a 

 species tolerates a wide range of salinity, a shift may 

 or may not occur. The assignment of a species in a 

 salinity zone was ultimately determined by where the 

 species has been regularly observed or captured. 



Species temporal distributions are often dependent 

 on annual climatic conditions and water currents. 

 Monthly distribution patterns were derived based on 

 the consistent presence of a life stage within a particu- 

 lar month. If a species was only present during un- 

 usual events (e.g., drought), it was not included in the 

 description of that species' distribution. However, if 

 a species regularly occurs, even during a restricted 

 time period, it was considered to be present for the 

 specific month(s). Greater temporal resolution, such 

 as on a biweekly rather than on a monthly basis, was 

 not feasible. 



Base ELMR Strengths and Weaknesses 



It is recognized that the ELMR methodology has both 

 strengths and weaknesses as a means to characterize 

 living marine resources. Therefore, the ELMR frame- 

 work and data base have been modified to take advan- 

 tage of the strengths, and to improve upon some of the 

 recognized weaknesses. 



The strengths of the ELMR methodology can be sum- 

 marized as: 



• Spatial and temporal framework enables synthe- 

 sis of information from disparate literature, data 

 sets, and expert knowledge. 



• Standardized species lists, estuary lists, and data 

 categories result in a consistent and versatile data 

 base with multiple applications. 



• The spatial and temporal framework allows si- 

 multaneous overview of many species and estu- 

 aries, enabling perception of emergent properties 

 and patterns of variation. 



The weaknesses of the ELMR methodology can be 

 summarized as: 



• Relative abundance rankings cannot be trans- 

 lated to actual densities or abundances of organ- 

 isms. 



46 



