Stoner and Davis: Outplanting queen conch. Strombus gigas 



393 



wild conch released at site CI were 80-117 mm SL 

 (mean=102, SD=8, n=2,552) and 85-117 mm SL 

 (mean=100, SD=7, re=2,543), respectively. For site C2, 

 the size ranges for hatchery and wild conch were 80- 

 117 mm SL (mean=101, SD=8, rc=2,540) and 83-117 

 mm SL (mean=101, SD=6, n =2,490), respectively. 



CL 



E 



F M A M 



1991 



Figure 3 



Bottom-water temperature recorded between 

 sites CI and C2, during the study period. Seven- 

 day averages for recordings made every 30 min- 

 utes are plotted. 



Table 1 



Density of juvenile queen conch (Strombus gigas) in 

 two field sites (CI and C2) prior to the release of 

 tagged conch (2 Mar. 1990), during the release ex- 

 periment, and at the end of the experiment (21 Feb. 

 1991). Density was measured by counting conch, 

 including tagged conch, in up to 20 randomly-se- 

 lected 4-m diameter circles ( 50 m 2 ) at each site. Mean 

 shell length for up to 100 individuals was measured 

 for conch found in each survey. Values are mean ± 

 SD(n). 



Date 



Number 

 of plots 



Density 

 (mm) 



Shell length 

 (no./m 2 ) 



Site CI 



2 Mar 90 



2 May 90 



16 Jul 90 



27 Nov 90 



21 Feb 91 



Site C2 



2 Mar 90 



2 May 90 



16 Jul 90 



20 



20 



20 



5 



6 



20 



20 

 20 



0.26 + 0.12 

 1.27 + 1.01 

 0.66 + 0.31 

 0.22 + 0.12 

 0.19 + 0.19 



0.01 + 0.01 

 0.03 + 0.03 

 0.62 + 0.74 



105+ 14(100) 



n a 

 111 + 12(100) 

 113+ 16(55) 

 129 + 13 (56) 



99+ 14(9) 



n/a 

 119 + 10(100) 



Tag recovery Tag recapture surveys were conducted 

 in June, September, and November 1990, to provide 

 a relative index of survivorship over time and space. 

 Searches encompassed the transplant sites, the zone 

 between the sites, and adjacent seagrass and sand 

 habitats. The search area was sectioned arbitrarily 

 (see insert, Fig. 2), and several divers using snorkel 

 or SCUBA gear drifted repeatedly side by side over 

 the area using the flood tidal current for transport. 

 Conch location was recorded by section, and searches 

 continued until no additional conch were found. Af- 

 ter each survey, all recaptured conch were returned 

 to their original transplant sites (CI or C2). Because 

 very few hatchery-reared conch remained alive in 

 February 1991, collections were made for shell 

 growth and morphology, but the complete survey was 

 not conducted. 



Tag recovery does not measure absolute 

 survivorship because of potential emigration from the 

 study site and possible inefficiency in finding tagged 

 animals; however, the search effort was intensive, 

 and clear water (usually >10 m horizontal visibility) 

 facilitated the efficiency of the searches. In two blind 

 tests 87 and 92% of 200 uniquely tagged conch were 

 recovered by using standard search procedure 

 (unpubl. data). The surveys were conducted over 

 periods from 7 to 20 days depending upon the num- 

 ber of divers available. Because of known limitations, 

 tag recovery data were used as a relative indicator of 

 survivorship in the two stock types and two study sites. 



Growth Seasonal growth rates (mmday -1 ) were 

 determined for three periods: summer (April to Sep- 

 tember 1990), fall (September to November 1990), 

 and winter (November 1990 to February 1991) by 

 comparing shell lengths of individual, tagged conch 

 at the beginning and end of the survey periods. 



Shell morphology At the beginning (1 April 1990) 

 and end of the experiment (20 February 1991), rep- 

 resentative samples of at least 30 hatchery-reared 

 and 30 wild conch (collected alive) were measured 

 for shell length and width, and shell and tissue 

 weight. Maximum shell width was the distance be- 

 tween the last complete spine formed near the shell 

 aperture and the spine on the opposite side of the 

 shell. Total weight of the shell and soft tissue (live 

 weight) was recorded to the nearest 0.01 g. After 

 freezing and subsequent thawing, the soft tissue of 

 the animal was extracted, lightly blotted, and 

 weighed. Weights of the clean, air-dried shells were 

 also recorded. 



Behavior Nine times during the study, observations 

 on burial behavior were made for the first 30 hatch- 



