• Juveniles and adults are the predominant life 

 stages present in estuaries, followed by larvae, 

 eggs, and spawning. 



• The number of species present as juveniles and 

 adults was highest from June through October, 

 and lowest from December through March, with 

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

 Atlantic herring). 



• The number of species present as larvae in the 

 mixing and seawater zones was highest in June. 



Mid-Atlantic Region. The location of the 22 se- 

 lected ELMR Mid-Atlantic estuaries are shown in 

 Figure 8 (next page), and the common and scientific 

 names of the 61 selected ELMR Mid-Atlantic spe- 

 cies are listed in Table 10 (p. 23). Results of the 

 ELMR study in the Mid-Atlantic region are summa- 

 rized in Distribution and Abundance of Fishes and 

 Invertebrates in Mid-Atlantic Estuaries, ELMR Report 

 No. 12 (Stone et al. 1994). Life history summaries 

 and tables are still being developed for the species 

 in this region. 



Long Island, Cape Cod, Martha's Vineyard, and 

 Nantucket Island were formed as end moraines 

 marking the southern extent of the most recent 

 Pliestocene glaciation. Sea levels rose as the gla- 

 ciers melted, drowning the mouths of rivers extend- 

 ing across the Mid-Atlantic continental shelf and 

 forming the estuarine systems present today (NOA A 

 1985a). Tides are semidiurnal, and range from 

 approximately two meters in Delaware Bay, to less 

 than a meter in tributaries of the Chesapeake Bay 

 (NOAA 1990a). 



The 61 species selected in the Mid-Atlantic region 

 are generally of the cold-temperate fauna of the 

 Virginian marine biogeographic province. Other 

 selected species have a freshwater origin, such as 

 the yellow perch and channel catfish common in the 

 low-salinity tidal tributaries of the Chesapeake Bay. 

 Diadromous species include Atlantic and shortnose 

 sturgeon, American eel, alewife, blueback herring, 

 American shad, and striped bass. Table 11 (p. 24) 

 readily conveys the occurrence of the selected 61 

 ELMR species in each of the 22 Mid-Atlantic estuar- 

 ies. This table depicts the highest relative abun- 

 dance of the adult or juvenile life stage of each 

 species, in any month, in any salinity zone within 

 each estuary. The spawning, egg, and larval life 

 stage categories are not considered. This table also 

 suggests the zoogeographic distribution of species 

 among Mid-Atlantic estuaries. For example, a few 

 northern species (Atlantic cod, Atlantic salmon) do 

 not occur in estuaries south of Long Island. Bay 



scallop does not occur in the low-salinity tributaries 

 of the Chesapeake, whereas channel catfish occur 

 primarily in estuaries with tidal riverine habitat. A 

 few eurythermal and euryhaline species such as 

 grass shrimp and silversides are ubiquitous, con- 

 sidered abundant or highly abundant in all Mid- 

 Atlantic estuaries. 



To examine seasonal patterns of species presence/ 

 absence in Mid-Atlantic estuaries, the numbers of 

 species present (ranked as "rare" or greater) were 

 counted by month and by salinity zone for the 

 adult, juvenile, larval, spawning, and egg life stages. 

 The original ELMR Mid-Atlantic data set (Stone et 

 al. 1994), with revisions for Massachusetts (RPI 

 1999) was used. In Figure 9, 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 appears to be lowest in 

 the tidal fresh zone. However, this is partially 

 due to the fact that the selected ELMR species 

 are primarily estuarine, not freshwater species. 

 In addition, the lack of systematic faunal sur- 

 veys in many tidal freshwater zones contribute 

 to this apparent lower diversity. 



• Juveniles and adults are the predominant life 

 stages present in estuaries, followed by larvae, 

 spawning, and eggs. 



• The number of species present as juveniles and 

 adults is generally highest from June through 

 October, and lowest from December through 

 March. 



• The number of species present as larvae in the 

 mixing and seawater zones is highest from May 

 through July. 



Text continues on p. 27. 



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