264 



Fishery Bulletin 104(2) 



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10 20 30 40 50 

 Station depth (m) 



Figure 2 



Seasonal average (SD) bottom tem- 

 perature in "C (A) salinity (B), den- 

 sity ((7,, Kg/m'') (C ) and stratification 

 (0, joules/m'^l (D) across the coast off 

 Georgia. The station numbers across 

 the top correspond to the cross-shelf 

 stations shown in Figure 1. 



across the entire shelf (Fig. 2A). In the summer, bottom 

 waters were warmest on the inner-shelf and cooler on 

 the outer-shelf (Fig. 2A). Average fall bottom water 

 temperature was intermediate between that of spring 

 and summer and was warmest on the outer-shelf (Fig. 

 2A). The lowest bottom water temperatures were mea- 

 sured during the winter on the inner-shelf (Fig. 2A). 

 Bottom salinity was lowest on the inner-shelf during 



all seasons (Fig. 2B). Bottom salinity was also low on 

 the inner- and mid-shelves during the spring and rose 

 to near 36 psu on the outer-shelf (Fig. 2B). During the 

 summer, fall, and winter the mid- and outer-shelf bottom 

 salinities remained near 36 psu (Fig. 2B). Bottom water 

 density reflected the seasonal and cross-shelf patterns 

 in temperature and salinity (Fig. 2C). Bottom water 

 density was greatest during the winter when water 

 temperatures were the lowest (Fig. 2C). In the spring, 

 a cross-shelf pattern occurred and density was lowest 

 inshore (Fig. 2C). During summer bottom water density 

 was lowest inshore, where the water temperatures were 

 low (Fig. 2C). There was no cross-shelf density pattern 

 in the fall (Fig. 2C). Water column stratification was 

 greatest during the summer and Simpson's stratification 

 numbers were always higher on the outer-shelf (Fig. 2D). 

 The low stratification numbers on the inner- and mid- 

 shelves (Fig. 2D) indicated that there was a high prob- 

 ability of vertical mixing in all seasons. 



Video analysis of the ROV tows indicated that the 

 cross-shelf bottom on the continental shelf off the coast 

 of Georgia consisted predominately of unconsolidated 

 sand sediments. Hard-bottom (rock rubble) was seen in 

 one video frame at station 2.3, on the southern edge of 

 the Gray's Reef NMS. No ROV data were collected at 

 the inner- or outermost stations; however, no hard-bot- 

 tom has been reported from either station (SEAMAP- 

 SA, 2001). These data indicate that unconsolidated 

 sediments were sampled. 



Cross-shelf patterns in the juvenile fish assemblages 



One hundred eighty one taxa were collected with the 

 beam trawl, and of these, 121 were classified as juveniles 

 (Appendix). Twelve strongly reef-associated species and 

 21 weakly reef-associated species were collected. The 

 assemblages exhibited a cross-shelf gradient and the 

 station groupings varied seasonally (Fig. 3). CA of both 

 the 10% and 1% data sets resulted in the same overall 

 patterns; however, rare species frequently were found 

 between station groups in the ordination. During the 

 spring, there were two cross-shelf station groups that 

 overlapped at station 4 (Fig. 3A), an inner and mid-shelf 

 group (stations 1-4), mainly inshore of the 30-m isobath, 

 and an outer-shelf group (stations 4-7). Eigenvalues of 

 the CA showed that the separation of the two groups 

 was mainly along the first dimension (Table 5). During 

 the summer, there was little cross-shelf pattern in the 

 assemblages. The only exception was station 2.3, which 

 was distinct from all other stations because live bottom 

 was sampled at that station (Fig. 3B). When this station 

 was removed from the analysis, there was no cross-shelf 

 pattern in the summer data set (Fig. 3C). Three cross- 

 shelf station groups were present in the fall (Fig. 3D): 

 inner-shelf (station 1), mid-shelf (stations 2-5), and 

 outer-shelf (stations 6-7). Separation of the groups was 

 predominately along the first dimension (Table 5), which 

 separated the inner- and mid-shelf station groups from 

 the outer-shelf station group. During the winter, there 

 was a cross-shelf gradient in the juvenile fish assem- 



