Sandt and Stoner: Ecology of earlyjuvenile Strombus gigas 



517 



Neighbor Cay in the southern Exuma Cays, Bahamas 

 (28°48.84'N, 76°11.9'W) (Fig. 1). The study site was 

 located between a section of shoreline beachrock and 

 subtidal carbonate rubble to the east and a sand bar 

 to the west which extended outward from the shore- 

 line (Fig. 2). Tidal currents ran parallel to shore and 

 increased from near zero at the shoreline to 50 cm/s or 

 greater 200 m from shore. The tidal range was 1.0 m. 



Distribution and abundance of conch was examined 

 along a 110-m section of nearshore shallow habitat (0- 

 1.9 m deep at mean low water). Several zones extend- 

 ing to 25 m offshore from the low water mark were 

 identified (Fig. 2). Zone A was intertidal, between high 

 and low water marks. Zone B consisted of the shallow- 

 est subtidal area extending from shore to the top of a 

 steep surf berm (zone C). Zone D was a sparsely veg- 

 etated transition area between either zone C (stations 

 1-7) or zone B (stations 8-12), and zone E. Zones A 

 through C were bare sand habitats. Zones E, F, and G 

 were areas vegetated with turtlegrass, Thalassia 

 testudinum Konig and small amounts of shoal grass, 

 Halodule wrightii Konig (Table 1). Measurements and 

 experiments in zone E were made 2.5 m from the in- 

 shore edge of the seagrass (Fig. 2). Measurements in 

 Zones F and G were made 10 and 20 m, respectively, 

 from the seagrass edge. The rocky area to the east was 

 a carbonate cobble covered with macroalgae including 

 an abundant turf of the green algae Cladophoropsis 



~*5 



', Study Site 7^ 



NEIGHBOR * k 

 ^ CAY ^\Vl 



EXUMA SOUND 



LEE -. 

 STOCKING 

 ISLAND 



82" 



_l 



^•? 6 °**^| 



Figure 1 



Map of the Lee Stocking Island area in the centra] Bahamas, showing the location of the 

 Neighbor Cay study site where earlyjuvenile queen conch were found. 



membranacea and Batophoro oerstedi, along with 

 clumps of the branched red algae Laurencia obtusa, L. 

 poitei, and Graciolaria compressa. The adjacent 

 seagrass area (zones E, F, G) is a known, long-term 

 (>5 years) nursery habitat for queen conch (>l-yr-old) 

 studied earlier bv Stoner and Sandt ( 1991). 



Methods and material 



Environmental measurements 



Sediment grain-size and organic content, two factors 

 frequently important in the distribution of infaunal ani- 

 mals, were measured in each zone (A to G) and along 

 each transect perpendicular to the beach where pos- 

 sible (Fig. 2). Sediments to 5.0cm depth were collected 

 in a 40-mm diameter core and frozen (-15°C) until analy- 

 sis. In the laboratory, one thawed sediment subsample 

 of approximately 100 g wet weight was dried for at least 

 24 hours in an oven at 80°C to constant weight and 

 incinerated at 550°C in a muffle furnace for 4 hours. 

 Organic content was estimated as the percent differ- 

 ence between dry weight and ash-free dry weight. A 

 second sediment subsample of approximately 50 g was 

 used to measure granulometric properties. Grain-size 

 for the sand fraction was determined by using standard 

 sieve procedures (Folk, 1966), after removing salts and 

 extracting the silt-clay fraction by washing with fresh- 

 water on a 62-um mesh screen. Silt- 

 clay fractions were analysed with a 

 standard pipet procedure (Galehouse, 

 1971). Product moment statistics 

 were generated for mean grain-size 

 (McBride, 1971). 



Relative cohesiveness of the sedi- 

 ment was measured in the field at 

 every non-rocky station by using a 

 50-cm-long steel rod (15.3 mm di- 

 ameter) equipped with a sliding 

 lead weight (1.3 kg) and a stop 

 17 cm above the end of the device. 

 The rod was placed vertically on the 

 surface of the sediment, the weight 

 was raised 25 cm on the steel shaft 

 and dropped. Penetration was mea- 

 sured in mm, and the average of 

 two measurements was recorded. 



Seagrasses, macroscopic detritus 

 (identified as being mostly senes- 

 cent seagrass blades), and macro- 

 algae were collected on transects 3, 

 5, 7, and 9 in the 3 vegetated zones 

 E, F, and G. Samples were collected 

 from a 25 X 25 cm quadrat into 

 3-mm mesh bags. Detritus and 



