116 



Fishery Bulletin 103(1 



Results 



Two dimensions were sufficient to explain the majority of 

 the variance in the larval concentration data (Table 4). 

 The winter data eigenvalues indicated the relevance of 

 a third dimension; yet, inspection of three dimensions 

 did not define any patterns not indicated by the first 

 two dimensions. Thus, two dimensions were analyzed for 

 each season in both the CA and CCA analyses. 



Cross-shelf patterns in the larval fish community 



A cross-shelf pattern in the larval community was 

 observed. In spring, summer, and fall, the inshore sta- 

 tions (stations 1-3) were in close proximity, forming an 

 inner-shelf station group in the ordination resulting 

 from the CA (Fig. 4). Along the same dimension (axis) 

 as the inner-shelf group was a mid-shelf station group of 

 stations 3-6 (stations 2.1-2.4 were also included in this 

 group in spring, summer, and winter). An outer-shelf 

 group composed of offshore stations (stations 5-7) was 

 distributed along a nearly perpendicular dimension, and 

 the mid-shelf group was at the intersection of the two 

 dimensions (Fig. 4). Analysis of the one-percent species 

 data set revealed an identical pattern for each season 

 (not shown). 



The winter station ordination resulted in a less dis- 

 tinct cross-shelf pattern (Fig. 4D). In January 2001, 

 stations 1, 2, 3, and 6 were in the inner-shelf group; 

 whereas, stations 4 and 7 from the same cruise were in 

 the mid-shelf group, and station 5 was in the outer-shelf 

 group. Some of this blurring of the cross-shelf pattern 

 in the ordination may be explained by a lower total 

 catch, giving the taxa found across the shelf {Brevoor- 

 tia tyrannus and Leiostomus xanthurus) more influence 

 over the data. In addition, most of the variance was 

 explained by the first dimension (Table 4), meaning that 

 the separation of the outer-shelf group (stations 5 and 

 6) from the mid- and inner-shelf groups is based on a 

 weak relationship among the stations. 



Larval assemblages associated with cross-shelf patterns 

 in the larval fish community 



Three larval assemblages were defined that corre- 

 sponded to the three station groups (Fig. 5). The inner- 

 shelf assemblage was composed of species that spawn in 

 coastal and estuarine habitats. Larvae in this assem- 

 blage were distributed within the 20-m isobath and con- 

 fined largely to stations classified as inner-shelf (Fig. 6). 

 The inner-shelf assemblage was primarily represented 

 by Menticirrhus americanus during spring, summer, 

 and fall, and by Micropogonius undulatus and Lagodon 

 rhomboides during winter (Table 5). Taxa included in 

 the mid-shelf assemblage were generally found between 

 the 20- and 40-m isobaths. Some mid-shelf taxa, how- 

 ever, were found across the shelf (stations 1-7) and a 

 large percentage of the larvae occurring in each region 

 were mid-shelf taxa (Fig. 6). The outer-shelf assemblage 

 comprised offshore or deepwater spawned taxa and was 



CA1 



Figure 4 



Correspondence analysis ordinations (portraying the first 

 and second dimension scores) of the larval fish community 

 data showing station groups in each season (A) spring, 

 (B) summer, (C) fall, and (D) winter. Three cross-shelf sta- 

 tion groups were identified within each season. Solid lines 

 enclose the boundary of each station group with three or more 

 stations. Station groups comprising one or two stations are 

 not enclosed by a solid line. Each station group is labeled and 

 portrayed with a different symbol. The dashed lines intersect 

 at the origin of the plot. Analyses were conducted with larval 

 concentration data only. Data from each cruise within a season 

 are shown together. 



