• Sciaenids (spotted seatrout, weakfish, spot, northern 

 kingfish, Atlantic croaker, black drum, and red drum): 

 Most sciaenids move to nearshore or offshore waters 

 for spawning, although some may spawn in passes. 

 Larvae may be transported toward estuaries, but typi- 

 cally attain juvenile size before they enter. Juveniles 

 develop in the nursery habitats of the bays, then 

 migrate out as subadults. Since some of these species 

 have rather long life spans, several years may be spent 

 in the estuaries as juveniles. As temperatures drop in 

 the winter, they move into deeper waters. Spotted 

 seatrout, Atlantic croaker, black drum, and red drum 

 are generally more abundant south of the Mid-Atlantic 

 region. 



• Mullets: For the purposes of this report, the ELMR 

 program has compiled information for striped mullet 

 (Mugil cephalus) and white mullet {M. curema) collec- 

 tively. Both species spawn in marine coastal waters 

 and enter estuaries to feed, and both species are 

 generally more abundant south of Cape Hatteras than 

 in the Mid-Atlantic region. Striped mullet ascend into 

 lower salinities more often than do white mullet, and 

 striped mullet are generally more abundant in Mid- 

 Atlantic estuaries than are white mullet. 



• Tautog and cunner: Spawning occurs in the seawa- 

 ter zones of Mid-Atlantic estuaries, and eggs are buoy- 

 ant. Juveniles remain in estuaries through the winter, 

 but may become inactive. Adults are often associated 

 with rocky reefs or mollusc beds. 



• American sand lance: Generally more abundant in 

 the northern Mid-Atlantic estuaries. Adults are demer- 

 sal and may burrow in sandy substrate. May co-occur 

 with the northern sand lance (Ammodytes dubius), but 

 A. dubius is primarily found in deeper offshore waters 

 (Nizinski et al. 1 990, Robins et al. 1 991 ). 



• Gobies: Forthepurposesof this report, information 

 on Gobiosoma species has been compiled collectively. 

 Three species of Gobiosoma occur in Mid-Atlantic 

 estuaries: naked goby (G. bosci), seaboard goby (G. 

 ginsburgi), and code goby (G. robustum) (Robins et al. 

 1991). The naked goby is most abundant in low to 

 moderate salinity waters, and is often associated with 

 oyster reefs or submerged aquatic vegetation. The 

 seaboard goby prefers higher estuarine salinities, and 

 is often found on oyster reefs. The code goby prefers 

 moderate to high salinities, but is relatively scarce in 

 the Mid-Atlantic region. 



• Butterfish: Butterfish may spawn in the seawater 

 zones of some estuaries in the summer, but they 

 typically move offshore to overwinter. Generally more 

 common in the northern Mid-Atlantic estuaries than in 

 the southern ones. 



• Flounders: Astheir names suggest, winter flounder 

 enter estuaries primarily in the winter months, whereas 

 summer flounder do so in the spring and summer. 



• Hogchoker: Spawning occurs primarily in the mixing 

 zone of estuaries, but juveniles may ascend into tidal 

 fresh waters and even well above the head-of-tide. 



Couplirig of Estuarine and Marine Ecosystems 



Classifying and Comparing Estuaries. Although the 

 qualitative nature of the distribution data precludes 

 statistical comparisons of species abundances among 

 estuaries, comparisons can be made using data on the 

 presence/absence of species in salinity zones. This 

 information, combined with the spatial and temporal 

 distribution data, is the strength of the ELMR data 

 base. Estuaries can be loosely categorized by their 

 physical and chemical characteristics and their associ- 

 ated species assemblages. The relative importance of 

 individual estuaries to specific species may also be 

 determined. 



The species found in an estuary are sensitive indica- 

 tors of both the mean and extreme environmental 

 conditions within that estuary. Estuaries can be clas- 

 sified by the number of species present and by whether 

 the fauna are primarily marine, estuarine, or freshwa- 

 ter. Species assemblages may correlate with physical 

 characteristics, such as substrate, vegetation, areal 

 and temporal characteristics of salinity zones. The 

 information on species presence/absence or other 

 attributes can be used to determine the faunal similari- 

 ties and differences among estuaries. 



A comparison of estuaries and associated species can 

 identif/ differing factors among those estuaries that 

 might account for shifts in species distribution and 

 relative abundance, helping to defin^j ecological vari- 

 ables controlling species distributions. For example, a 

 species may show differing salinity tolerances among 

 estuaries, suggesting that some other factor, such as 

 temperature, competition, or predation may be regulat- 

 ing its distribution. 



Linkages to Marine Ecosystems. Estuaries provide 

 a year-round home to many aquatic species; however, 

 a large number of species use estuaries for specific 

 parts of their life histories and spend the rest offshore. 

 Most of these latter species fall into four general 

 categories: 1) diadromous species, which use estuar- 

 ies as migration corridors and, in some instances, 

 nursery areas; 2) species that use estuaries for spawn- 

 ing, often at specific salinities; 3) speciesthat spawn in 

 marine waters near the mouths of estuaries and de- 

 pend on tidal and wind-driven currents to carry eggs, 

 larvae, or early juveniles into estuarine nursery areas; 



16 



