392 



Fishery Bulletin 92(2), 1994 



ine the density of conch at the end of the experiment, 

 and to observe movements by the population. On each 

 date up to 100 conch were measured for shell length 

 (apex to siphonal canal). 



Seawater temperature for the study site was re- 

 corded with a Ryan Temp Mentor placed on the bot- 

 tom between sites CI and C2. Temperature was re- 

 corded (+ 0.2°C) every 30 minutes, and seven-day mean 

 temperatures were calculated for plotting (Fig. 3). 



Experimental animals 



Approximately 6,000 wild and 6,000 hatchery-reared 

 conch were used in the experiments described be- 

 low. Wild conch were collected from the Children's 



D> 



— i — 



76°06- 



'76°0A 



23°46' 



WINDSOCK 

 CAY | 



GREAT BAHAMA 

 BANK 



Bay Cay nursery site (CI); all were between 85 and 

 120 mm shell length (SL). Hatchery-reared conch 

 were purchased from Tradewind Industries, Ltd. 

 (Caicos Conch Farm) in Providenciales, Turks, and 

 Caicos Islands. These conch originated from 12 egg 

 masses collected near Providenciales in the summer 

 of 1988. The larvae were fed with Caicos Isochrysis 

 and postlarvae with flocculated Chaetoceras gracilis 

 and blended Enteromorpha sp. (Davis et al., 1992). 

 Between December 1988 and March 1989, 50-mm 

 juveniles were transplanted to a protected nursery 

 habitat near the hatchery (Davis and Dalton, 1991). 

 Between 26 and 29 March 1990, 6,000 hatchery- 

 reared conch comparable in size to the 1+ year class 

 conch native to Children's Bay Cay nursery (85-120 

 mm SLKTable 1) were collected from the 

 grow-out area and held in two 8 x 8 m 

 holding pens. On the morning of 30 

 March the conch were loaded into 32 

 large burlap sacks wrapped in plastic 

 bags and transported via cargo plane 

 to Lee Stocking Island. The conch were 

 kept cool and moist during the 7-hour 

 period out of the water. Upon arrival, 

 conch were immediately taken to either 

 site CI or C2. The plastic was removed 

 and the burlap bags were placed on the 

 bottom of the respective sites. On 31 

 March they were released into two tem- 

 porary pens ( 10 m 2 ) already constructed 

 at each of the study sites. All hatchery- 

 reared conch were tagged and measured 

 over the next 10 days. Wild conch were 

 tagged and placed in temporary pens 

 during a 10-day period prior to the ar- 

 rival of the hatchery-reared conch. 



All conch were marked with orange 

 spaghetti tags ( Floy Manufacturing Co. ) 

 tied around the spire, and total shell 

 length was measured to the nearest mil- 

 limeter (±1 mm) with calipers. Tags 

 were both letter coded and numbered 

 so that conch type and release site could 

 be identified immediately in the field. 



CHILDREN'S 

 BAY CAY 



23°44- 



Figure 2 



Map of Lee Stocking Island and Children's Bay Cay in the southern 

 Exuma Cays, Bahamas. Study sites CI and C2 are shown as squares, 

 the dotted line around CI represents the approximate boundaries of 

 the natural queen conch, Strombus gigas, population in July 1990. 

 The lower insert shows the geographic zones surveyed during each 

 tag recovery. 



Free-ranging experiment 



Hatchery-reared and wild tagged conch 

 were haphazardly released throughout 

 each of the two 100 m x 100 m experi- 

 mental sites (CI and C2) to examine 

 survivorship, growth, morphology, and 

 behavior of free-ranging juveniles be- 

 tween 1 April 1990 and 20 February 

 1991. The size ranges for hatchery and 



