Abstract. A survey of queen 



conch [Strombus gigas) popula- 

 tions near Lee Stocking Island, 

 Exuma Cays, Bahamas, showed 

 that 74% of all adults were on the 

 narrow island shelf adjacent to the 

 Exuma Sound, in 10-18 m of wa- 

 ter. None were found deeper than 

 25 m, and relatively few adults 

 were found shallower than 10 m. 

 Numbers of juveniles were great- 

 est on the Great Bahama Bank 

 and decreased with increasing 

 depth on the island shelf. No juve- 

 niles were found in shelf regions 

 greater than 15 m in depth. Pat- 

 terns of shell morphology, which 

 were related to growth rates in 

 juveniles, suggest that adults that 

 mature on the Great Bahama 

 Bank rarely move to deep water, 

 and that the most important 

 sources for deep-water stocks are 

 small, nearshore nurseries on the 

 island shelf. The mostly unfished 

 deep-water populations are prob- 

 ably now the primary source of 

 larvae for queen conch in the 

 Exuma Cays. Because virtually all 

 of the conch are within the limits 

 of SCUBA diving, it will be impor- 

 tant to identify and to protect criti- 

 cal nursery habitats for reproduc- 

 tive stocks. 



Queen conch, Strombus gigas, 

 reproductive stocks in the central 

 Bahamas: distribution and 

 probable sources 



Allan W. Stoner 

 Kirsten C. Schwarte 



Caribbean Marine Research Center. 805 E 46th Place 

 Vera Beach, Florida 32963 



Manuscript accept 8 September 1993 

 Fishery Bulletin 92:171-179 (1994) 



Queen conch (Strombus gigas), 

 once abundant throughout the Car- 

 ibbean region, have been fished to 

 near extinction or to a level at 

 which there is no longer a viable 

 fishery in many localities (Appel- 

 doorn et al., 1987; Berg and Olsen, 

 1989). This is particularly true in 

 nations where the fishery has been 

 open to SCUBA divers. Stock 

 depletion resulted in at least tem- 

 porary closures of the conch fishery 

 in Bermuda, Florida, Cuba, Bon- 

 aire, and the U.S. Virgin Islands. 

 Regulations including size limits, 

 catch quotas, gear restrictions, and 

 closed areas have been instituted 

 in other countries. 



This study was conducted in an 

 attempt to understand reasons for 

 the rapid depletion of queen conch 

 populations in the Caribbean re- 

 gion, and to evaluate the signifi- 

 cance of deep-water conch stocks. 

 Several authors have suggested 

 that these deep-water conch, living 

 beyond the normal range of free 

 divers, are the primary source of 

 larvae for shall-water populations 

 and the fishery (Berg and Olsen, 

 1989; Wicklund et al., 1991; Stoner 

 et al., 1992; Stoner and Sandt, 

 1992). Therefore, we surveyed the 

 density and age structure of queen 

 conch in the vicinity of Lee Stock- 

 ing Island in the central Bahamas. 

 Differences in shell morphology 

 and growth rate between conch 

 found on Great Bahama Bank and 



on the windward island shelf adja- 

 cent to Exuma Sound were used as 

 indicators of geographic source for 

 reproductive stocks. The impor- 

 tance of deep-water populations is 

 discussed in terms of fisheries 

 management. 



Methods and materials 



Study site 



An assessment of the adult conch 

 population was conducted between 

 1989 and 1991 in a 12-km long sec- 

 tion of the Exuma Cays, central 

 Bahamas, adjacent to Lee Stocking 

 Island (Fig. 1). To the west and 

 south of the Cays lies the Great 

 Bahama Bank, a shallow, sand- 

 and seagrass-covered platform that 

 extends to the Tongue of the Ocean. 

 To the east and north is a narrow 

 (1-2 km) island shelf, a steep shelf- 

 break beginning at an approxi- 

 mately 30-m depth, and the deep 

 Exuma Sound. 



Great Bahama Bank in the re- 

 gion of the study site is character- 

 ized by strong tidal currents that 

 carry oceanic water from Exuma 

 Sound onto the bank through chan- 

 nels between the islands. Approxi- 

 mately 909r of the bank area is less 

 than 3.5 m deep; the remainder is 

 tidal channels with depths to 8 m 

 near the inlets and between the 

 Brigantine Cays. For this study the 



I 71 



