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Fishery Bulletin 96(4), 1 998 
for 4 h to determine organic content, calculated as 
the percent difference between dry weight and ash- 
free dry weight. A second rinsed subsample ( —20 g) 
was analyzed by using standard dry sieve procedures 
(Folk, 1966), and product moment statistics were 
used to calculate mean grain size (McBride, 1971). 
The silt-clay fraction (>4.0 0, <62 mm), always < 9% 
of sediment dry weight, was not fractionated. 
Replicate dredge sample plots (n-5 for all stations, 
except C3, where n= 6) were delineated by a circular 
enclosure made of aluminum sheet metal (area=0.5 
m 2 , height=0.3 m) that was placed haphazardly at 
each station. The enclosure was pushed securely into 
the sediment to prevent escape of motile fauna. In 
the middle of each sample plot, the number of 
Thalassia testudinum shoots was counted in a quad- 
rat (25 x 25 cm). A gasoline-powered suction dredge 
(modified from Brook, 1979) was used to collect year- 
class 0 queen conch, other macrofauna, and associ- 
ated macrophytes from each plot. The dredge cre- 
ated high-pressure water flow which, as a result of 
Venturi principle, drew algae, detritus, sediments, 
and macrofauna through a PVC intake tube (dia- 
meter=7.6 cm) into a mesh bag (40 x 70 cm, 1.2 mm 
mesh). Preliminary sampling in the study area and 
observations of year-class 0 conch ( <45 mm SL) indi- 
cated that conch in the nursery ground buried no 
deeper than 5 cm into the sediment. Therefore, sedi- 
ments from plots with seagrass were removed to the 
depth at which T. testudinum rhizomes occurred (usu- 
ally 8-15 cm); in bare sand, dredging was 8-10 cm 
deep. Unlike the other macrophytes, living seagrass 
did not detach easily and was not collected with the 
dredge material. The mesh bags holding the dredged 
materials were tied securely underwater and later 
fixed in a 10% formalin-seawater mixture contain- 
ing rose bengal as a staining agent. After 24 hours, 
each sample was rinsed onto a sieve (1.2 mm) and 
preserved in 70% ethanol until sorted. 
Macrophytes were sorted into three components: 
T. testudinum detritus (senescent blades and frag- 
ments), the green macroalga Batophora oerstedi, and 
the red algae Laurencia spp. Occasionally fronds of 
calcareous green algae (including Halimeda spp., 
Penicillus capitatus, Udotea spp., and Rhipocephalus 
phoenix) were collected, but they were sparsely dis- 
tributed and not quantified. Each fraction was rinsed 
with freshwater to remove salts and dried at 80°C to 
constant weight (~24 h) so that biomass (g dry wt/ 
m 2 ) could be calculated. 
For ease in extracting newly settled queen conch 
and their potential predators, sediments were divided 
into two fractions, those retained on 1.2- and 2.0- 
mm sieves. A conch was classified as alive if its soft 
tissue and operculum were intact. Shortly after 
death, the operculum detaches from the foot, and soft 
tissues decompose quickly. Therefore, dead and liv- 
ing conch were easily distinguished. We do not be- 
lieve that conch shells were damaged during collec- 
tion because the dredge apparatus lifted samples off 
the bottom by suction that could be controlled and 
the materials collected did not pass through an 
impellor. Care was also taken so that the fauna were 
not damaged in sieving. None of the conch classified 
as alive at collection had damaged shells, and most 
other taxa, such as polychaetes and crabs, were in 
good (i.e. whole) condition. 
To gain insight into modes of predation, shells of 
dead conch were classified as 1) whole and undam- 
aged, 2) drilled, 3) peeled back along the spire line, 
or 4) crushed. Whole shells of dead conch were at- 
tributed to predation by mollusks or asteroids ( Jory, 
1982; Iversen et ah, 1986; Ray and Stoner, 1995), 
drilled shells were probably the result of mollusk kills 
(Vermeij, 1987), and peeled and crushed shells were 
attributed to crustaceans (Randall, 1964; Vermeij, 
1982, 1987; Davis, 1992). Whole shells can also re- 
sult from nonpredatory mortality. The proportion of 
dead individuals was used as an indicator of post- 
settlement mortality. 
Whole shells (from both live and dead conch) were 
measured for shell length. When only a shell spire 
or shell aperture was found, total shell length for the 
dead animal was calculated on the basis of regression 
formulae derived from measurements of 20 whole shells 
ranging in size from 3 to 40 mm total length: 
Length = ( spire length x 2.4) - 1.8; [r 2 =0.991] 
Length = ( aperture length x 1.6) + 0.5. [r 2 =0.998] 
Given that queen conch settle into nursery grounds 
during a distinct season, it was possible to determine 
if an individual had indeed settled in 1992 on the 
basis of its size, color, and the amount of biological 
encrustation. Settlement of queen conch can occur 
at the beginning of May, and growth rates during 
the early postsettlement period may be as great as 
0.45 mm/d (Ray and Stoner, 1994); therefore, we con- 
sidered conch <45 mm in total shell length to be 
members of year-class 0. Also, conch shells lose their 
pink interior color within a few weeks after death. 
Animals that settled in 1992 were easily discerned 
on the basis of shell size and color. 
Xanthid and portunid crabs and alpheid shrimps 
were extracted from samples because they were 
abundant and known to be significant predators of 
postsettlement conch (Ray-Culp et al., 1997). Olivid 
and marginellid gastropods were also removed and 
counted as potential predators. Carapace width (includ- 
