usually offshore. 



• Gray snapper. Juveniles are typically associated 

 with vegetatbn in estuaries, particularly seagrass 

 beds and mangroves. Adults, spawning, eggs, 

 and larvae are usually offshore. 



• Sheepshead: Spawning occurs in nearshore 

 and inlet waters. Larvae are transported towards 

 the estuaries, but usually juvenile size is reached 

 before they enter. 



• Pin fish: Juveniles are the predominant life stage 

 within estuaries. Adults, spawning, and eggs are 

 usually offshore. Larvae are transported to 

 inlets, but usually attain juvenile size before they 

 enter bays. Subadults and adults may remain in 

 some bays before migrating out to spawning 

 grounds. 



• Sciaenids: Most sciaenids move to nearshore 

 or offshore waters for spawning, although some 

 may spawn in passes . Larvae may be transported 

 toward estuaries, but may 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. 



• Striped mullet. Estuarine habitat is primarily 

 used by juveniles and adults. They spawn 

 offshore or near passes, and larvae move inshore 

 and into estuaries. 



• Codegoby. Usually associated with seagrasses 

 and higher salinities. 



• Spanish mackerel. Juveniles and aduttsoccurin 

 estuaries, but other life stages are pelagic and 

 primarily offshore. 



• Flounders. Previously identified gulf flounder 

 have been re-examined and re-identified. Dr. 

 Thompson (pers. comm.) considered most of 

 the specimens to have been southern flounder, 

 reducing the estimated abundance of gulf 

 flounder in Louisiana estuaries. Spawning, eggs, 

 and larvae are in nearshore waters. Juveniles 

 and larvae migrate into bays for growth and 

 development. Gulf flounder appear to be less 

 likely to ascend into lower salinity water, typically 

 remaining in salinities greater than 20 ppt. 

 Southern flounder are widely distributed. 

 Juveniles and adults migrate according to 



temperature, creating "fall runs" to the offshore 

 waters. 



Use of ELMR Data 



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 data 

 base. Estuaries can be loosely categorized by their 

 physical and chemical characteristics and their 

 associated species assemblages. The relative 

 importance of individual estuaries to specific species 

 may also be determined. 



The species found in an estuary are sensitive 

 indicators of both the mean and extreme 

 environmental conditions within that estuary. 

 Estuaries can be classified by the number of species 

 present and by whether the fauna are primarily 

 marine, estuarine, or freshwater. Species 

 assemblages may correlate with physical 

 characteristics, such as txDttom substrate, vegetation, 

 and areal and temporal characteristics of salinity 

 zones. The information on species presence/absence 

 or other attributes can be used to determine the 

 faunal similarities and differences among estuaries. 



A comparison of estuaries and associated species 

 can identify differing factors among those estuaries 

 that might account for shifts in species distribution 

 and relative abundance, helping to define ecological 

 variables controlling species distributions. For 

 example, a species may show differing salinity ranges 

 among estuaries, suggesting that some otherfactor, 

 such as temperature, competition, or predation may 

 be regulating its distribution. 



Linkages to Marine Ecosystems. Estuaries are 

 home to many aquatic species year-round ; however, 

 a large number of species only 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 estuaries as migration corridors and, in some 

 instances, nursery areas; 2) speciesthat use estuaries 

 for spawning, often at specific salinities; 3) species 

 that spawn in marine waters near the mouths of 

 estuaries and depend on tidal- and wind-driven 

 currents to carry eggs, larvae, or early juveniles into 

 estuarine nursery areas; and 4) species that enter 

 estuaries during certain times of year to feed on 

 abundant prey. The importance of an estuary can be 

 assessed by the intensity with which species use 



14 



