Stoner et at: Recruitment of Strombus gigas 
895 
350 
300 
250 
200 
150 
100 
50 
0 
350 
300 
250 
200 
150 
1 00 
50 
0 
Xanthidae (F (1045) = 36.1; P < 0.001) 
A B C3 D3 E F Cl C2 C3 D1 D2 D3 D4 
Total predators (F (1045) = 22.5; P < 0.001) 
A B C3 D3 E F Cl C2 C3 D1 D2 D3 D4 
Down flow field 
Across flow field 
Stations 
Figure 4 (continued) 
benthic invertebrates when settlement occurs in low 
density 
After an extensive review of the literature, Butman 
(1987) concluded that settlement patterns in inver- 
tebrates associated with soft sediments are a func- 
tion of passive accumulation and deposition of lar- 
vae over spatial scales of kilometers and that active 
habitat selection occurs primarily over smaller scales 
(centimeters to meters). Data on the abundance of 
queen conch veligers over the Shark Rock tidal flow 
field (Stoner and Davis, 1997) may support this con- 
clusion . Although newly hatched larvae ( 300-500 p m ) 
were collected well beyond the Shark Rock nursery, 
at station F on 12 of 13 sampling dates in 1992, nei- 
ther midstage larvae (500-900 pm), competent lar- 
vae (>900 pm), nor newly settled conch were ever 
collected there, suggesting that late-stage larvae are 
somehow concentrated at the nursery location. At 
maximum flood-tide current, velocity near the sur- 
face decreases by approximately 75% between sta- 
tion A, north of Lee Stocking Island, and Shark Rock. 
Near the bottom, the decrease in velocity is more than 
95% (Stoner and Ray-Culp 1 ). We also know that 
maximum flood tidal excursion in this flow field oc- 
curs near the Shark Rock nursery area on neap tide; 
therefore, the nursery is bathed in oligotrophic wa- 
ter (and perhaps larvae) from the Exuma Sound on 
every tide, whereas areas farther out on the bank 
are not (Jones, 1996; Stoner et al., 1996b). These 
hydrographic characteristics may result in the depo- 
sition of larvae in the long-term nursery area, or the 
lower botom-water velocities may allow them to 
settle. 
Density of newly settled conch had a strong nega- 
tive correlation with distance from the center of the 
traditional nursery ground but was relatively inde- 
pendent from all other environmental characteris- 
tics tested (i.e. depth and various qualities of sedi- 
ments, seagrass, and macroalgae). This finding in- 
dicates that conch settlement cannot be explained 
1 Stoner, A. W., and M. Ray-Culp. 1997. Northeast Fisheries 
Science Center, Natl. Mar. Fish Serv., NOAA, 74 Magruder 
Road, Highlands, NJ 07732. Unpubl. data. 
