890 
Fishery Bulletin 96(4), 1998 
Table 2 
Macrophyte characteristics for 1 1 dredge stations in the Shark Rock flow field (see Fig. 1). Shoot count and detritus values are for 
Thalassia testudinum. All values are mean ±SE (n= 5 for all stations except C3, where n= 6). Data for stations C3 and D3 are given 
twice for ease of comparison in both flow-field dimensions. 
Station 
Shoot density 
(no./m 2 ) 
Biomass (g dry wt/m 2 ) 
Detritus 
B. oerstedi 
Laurencia spp. 
Down flow field, midchannel 
A 
784 ± 36 
353 ± 49 
0.02 ± 0.01 
0.20 ± 0.05 
B 
640 ± 65 
144 ± 20 
0.80 ± 0.40 
0.04 ± 0.03 
C3 
536 ± 26 
30 ± 11 
0.007 ± 0.004 
0.20 ± 0.18 
D3 
528 ± 36 
139 ± 20 
24.08 ± 6.00 
0.84 ± 0.27 
E 
352 ± 22 
29 ± 10 
44.76 ± 4.77 
0.66 ± 0.13 
F 
320 ± 17 
34 ± 8 
2.18 ± 0.57 
0 ± 0 
Across flow field 
Transect C 
Cl 
0 ± 0 
0.06 ± 0.04 
0.02 ± 0.03 
0 ± 0 
C2 
288 ± 44 
37 ± 14 
1.76 ± 0.45 
0.34 ± 0.18 
C3 
536 ± 26 
30 ± 11 
0.007 ± 0.004 
0.20 ± 0.18 
Transect D 
Dl 
0 ± 0 
0.08 ± 0.04 
0.06 ± 0.04 
0 ± 0 
D2 
240 ± 36 
14 ± 4 
3.68 ± 0.32 
1.60 ± 0.04 
D3 
528 ± 36 
139 ± 20 
24.08 ± 6.00 
0.84 ± 0.27 
D4 
544 ± 22 
180 ± 17 
0.22 ± 0.23 
1.58 ± 0.83 
tended in the sampling design. A similar increase 
occurred with T. testudinum detritus, with the ex- 
ception of a relatively low value at station C3 (Table 
2), where the aggregation of year-class 1 and 2 juve- 
nile conch undoubtedly had a grazing effect (Fig. 1). 
As was intended, shoot density and detritus biom- 
ass increased across transect D, and values were 
highest at station D4. Algal biomass was noticeably 
high only at stations D3 and E (where standing crops 
of Batophora oerstedi were 24 and 45 g dry wt/m 2 , 
respectively), and particularly low at station C3 
(grazed by conch). Biomass of Laurencia spp. was 
low at all stations (<1.6 g dry wt/m 2 ). 
Newly settled conch 
Newly settled queen conch were collected in dredge 
samples at all 11 stations except F (Fig. 2). Down 
the flow field, mean total density was relatively high 
(8-12 conch/m 2 ) at stations B, C3, and D3, and low 
(0-2.4 conch/m 2 ) at stations A, E, and F, although 
differences were only significant between C3 and F 
(Fig. 2). There was a significant negative correlation 
between total conch and distance from the geographic 
center of the long-term aggregation (Table 3); both 
total density and density of dead conch decreased 
with distance from C3 (Fig. 2). All of the conch col- 
lected at stations A and E were dead, as were most 
(60-86%) from the other down flow field stations. Live 
conch were collected at stations B, C3, and D3, with 
maximum density (4 conch/m 2 ) observed at B. 
Across the flow field, mean total conch density 
appeared to increase with seagrass density in 
transect C (Fig. 2), although differences were not sig- 
nificant. Values were relatively uniform at all of the 
stations in transect D, ranging from 4.0 to 8.4/m 2 . 
Live newly settled conch were most abundant at sta- 
tions C3 (1.7/m 2 ) and D3 (1.6/m 2 ), where seagrass 
density was moderate. Significant numbers of live 
individuals were also collected at the other stations 
with at least some seagrass (C2, D2, D4). However, 
all of the conch dredged from the bare sand stations 
(Cl, Dl) were dead. 
When data for 11 stations were included in the 
analysis, live conch density (the index of recruitment) 
had a significant positive correlation with total conch 
density (the index of settlement) (coefficient of cor- 
relation [r]=0.703, P=0.016). The percentage of the 
total conch that were dead provides an index of mor- 
tality. This index was negatively correlated with 
settlement (r=0.654, P=0.04). 
Live individuals ranged in size from 3.3 mm to 38.5 
mm with the mode at 10-14.9 mm (Fig. 3). Dead in- 
dividuals ranged in shell length from 1.5 to 44 mm 
with the mode at 1.0-4. 9 mm. The percentage of dead 
conch with whole, undamaged shells decreased across 
the flow field along both transects in the direction of 
increasing seagrass density and increasing density of 
