Marancik et al.: Fish assemblages on the southeast United States continental shelf 



125 



B 



Summer 



□ 



•o 



□ 



**-, 



 o 



Jooo 



'Vl 



3*)j 



D 



Winter 



O *«,,, 



'Joo, 



'■^ 



A>u? 



Fish abundance 

 (larvae/100 m 3 ) 





 • 0.001-1 



£ 1.001-10 

 ft 10.001-100 



100.001-1000 



Figure 13 



Distribution of Auxis rochei in (A) spring, (B) summer, and distribution of Cera- 

 toscopelus maderensis in (C) spring ID) winter, across the shelf and across water 

 masses. Transects for each cruise within a season are offset from one another. The 

 size of the circle for each station varies with fish concentration (larvae/100 m 3 ). 

 The fill color for each circle varies with water mass. 



Winter-spawning species that use estuaries are fre- 

 quently grouped together as "estuarine-dependent" taxa 

 (sensu Warlen and Burke, 1990). However, Hare and 

 Govoni 1 found that vertical distributions of these winter 

 taxa are different. In addition, our study demonstrated 

 that the horizontal distributions of these species are 

 distinct: Lagadon rhomboides and Micropogonias un- 

 dulatus were members of the inner-shelf assemblage 

 and Leiostomus xanthurus, Myrophis punctatus, and 

 Brevoortia tyrannus were members of the mid-shelf 

 assemblage. These findings imply that often grouped 

 "estuarine-dependent" species have different spawning 



locations or experience different larval transport pro- 

 cesses (or both) and may not reflect a single group. 



The definition of three regions based on larval fish 

 distributions is consistent with the division of the shelf 

 into three cross-shelf zones based on physical dynamics. 

 The inner-shelf (0-20 m) is dominated by freshwater 

 discharge, tides, and winds; the mid-shelf (20-40 m) 

 is influenced by wind and tides; and the outer-shelf 

 (40-75 m) is affected by the Gulf Stream and wind (At- 

 kinson and Menzel, 1985; Pietrafesa et al., 1985a, 1985b; 

 Lee et al., 1991; Boicourt et al., 1998). Thus, the physical 

 dynamics of the shelf appear to be closely linked to spa- 



