Abstract.— Reproductive behav- 

 ior and larval abundance of queen 

 conch Stromhus gigas L. were inves- 

 tigated near Lee Stocking Island, 

 Bahamas, with the primary purpose 

 of determining relationships between 

 physical variables, spawning frequen- 

 cy, and larval abundance. Monthly 

 observations made by divers at the 

 offshore spawning site showed that 

 copulation increased as a linear func- 

 tion of bottom water temperature 

 from April until the end of July, 

 when maximum summer tempera- 

 ture was reached. Pairing, copula- 

 tion, and egg-laying were all posi- 

 tively correlated with photoperiod 

 throughout the study period. The last 

 pairing and copulating conch were 

 observed in the middle of the warm- 

 est period in August suggesting that 

 stimuli other than temperature, such 

 as declining photoperiod, induce the 

 end of reproductive activity. The last 

 egg mass was found in early October. 

 There was a significant correlation 

 between spawning activity at the off- 

 shore reproductive site and larval 

 abundance in the adjacent downcur- 

 rent inlet. The first conch veligers 

 were found in plankton tows made 

 in early June, five weeks after the 

 first egg masses were observed at 

 the end of April. High larval density 

 was confined to July and August. Ad- 

 vanced-stage larvae, close to meta- 

 morophosis, were found only in the 

 vicinity of a shallow, benthic nursery 

 habitat. Comparison of reproductive 

 season in queen conch populations of 

 the Caribbean region showed no lati- 

 tudinal trend. In all areas, reproduc- 

 tion was associated with long days 

 and warm temperatures. Production 

 of conch larvae at the time of high 

 water temperature and steady trade 

 wind conditions may promote rapid 

 larval development and facilitate 

 transport of the vehgers to inshore 

 nursery habitats. 



Seasonality in reproductive activity 

 and larval abundance of queen 

 conch Strombus gigas 



Allan W. Stoner 

 Veronique J. Sandt 

 Isabelle F. Boidron-Metairon 



Caribbean Marine Research Center 



805 46th Place East, Vero Beach, Florida 32963 



Manuscript accepted 31 January 1992. 

 Fishery Bulletin, U.S. 90:161-170 (1992). 



The queen conch Strombus gigas L. 

 is the second most important fisher- 

 ies species in the Caribbean region, 

 after spiny lobster Panulirus argus 

 (Brownell and Stevely 1981). Conse- 

 quently, its general life history is well 

 known (Randall 1964, Brownell and 

 Stevely 1981, Berg and Olsen 1989). 

 Sexes are separate and sexual matur- 

 ity occurs at about 3V2 years of age, 

 a few months after the flared lip is 

 formed (Egan 1985, Wilkins et al. 



1987, Appeldoorn 1990). Fertilization 

 is internal and copulation may pre- 

 cede spawning by several weeks 

 (D'Asaro 1965). An individual female 

 may spawn six to eight times during 

 a single reproductive season (Davis 

 and Hesse 1983). An egg mass, usu- 

 ally laid on clean, coral sand, takes 

 24-36 hours to produce and consists 

 of a single continuous egg-filled tube 

 folded upon itself to form a kidney- 

 shaped aggregate of eggs and sand 

 about 15cm in length. Robert- 

 son (1959) estimated that between 

 385,000 and 430,000 eggs were laid 

 in a single egg mass. Eggs hatch 

 after 5-6 days; pelagic veligers re- 

 main in the water column for 18-40 

 days prior to metamorphosis (Randall 

 1964, D'Asaro 1965, Brownell 1977, 

 Davis et al. 1987, Boidron-Metairon 



1988, Mianmanus 1988). 

 Reproductive seasonality in queen 



conch has been reported for different 

 sites within the Caribbean region (see 

 Fig. 6), but the mechanisms which 

 regulate reproductive behavior are 

 poorly known. In this study, we pro- 



vide the first report on abundance 

 and seasonality of queen conch veli- 

 gers in the field, and examine re- 

 lationships between adult habitat, 

 reproductive activity, temperature, 

 photoperiod, and larval abundance. 



Methods and materials 

 Study site 



This study was conducted near Lee 

 Stocking Island (southern Exuma 

 Cays), Bahamas, an area known for 

 high abundance of queen conch (Fig. 

 1). The islands and cays of the Exuma 

 chain are bordered on the west by the 

 shallow Great Bahama Bank (mean 

 depth ~3m) and on the east by the 

 deep Exuma Sound. Waters from the 

 Exuma Sound flow onto the Bank 

 through numerous passes on the 

 flood tide and are mixed with Bank 

 water by wind-driven circulation. 

 Surface drogue studies (N.P. Smith, 

 Harbor Branch Oceanogr. Inst., Fort 

 Pierce, FL 34946, unpubl. data) in- 

 dicate that at the north end of Lee 

 Stocking Island, water flows through 

 Adderley Cay cut toward Shark 

 Rock. At the south end of the Island, 

 water flows through Rat Cay cut to 

 the west between Barraterre Island 

 and Children's Bay Cay. Most juve- 

 nile queen conch are located in shal- 

 low seagrass habitats on the Exuma 

 Bank; largest populations are found 

 near Shark Rock and southwest of 

 Children's Bay Cay. 



In Exuma Sound, approximately 

 1km to the east of Lee Stocking 



161 



