Stoner and Ray: Strombus gigas in a marine fishery reserve 



563 



pressure but also from natural accumulation of lar- 

 vae. Furthermore, given the surrounding current 

 patterns, the reserve is probably not large enough to 

 hold a self-sustaining conch population; conch at WW 

 are derived from up-stream spawning stocks located 

 outside the reserve. With a northwest current along 

 the Exuma Cays shelf, an MFR located farther to 

 the south might actually allow better downstream 

 conservation of queen conch. However, exact trans- 

 port distances are unknown, and calculations are 

 complicated by the potential effects of numerous tidal 

 passes and plumes. Because preservation of exter- 

 nal sources of larvae will be critical to the mainte- 

 nance of populations within any park, managers es- 

 tablishing all such reserves must consider the broad 

 metapopulation context (Carr and Reed, 1993; Man 

 etal., 1995). 



It is likely that the high densities of larvae exported 

 from the Exuma Park on the northwest current rep- 

 resent a significant recruitment source for conch 

 populations in the northern Exuma Sound. Very large 

 aggregations of juvenile conch (>600 ha) were mea- 

 sured in the northern Exuma Sound near the Schoo- 

 ner Cays in 1993 (Stoner, unpubl. data). These popu- 

 lations appear to have increased since the establish- 

 ment of the Exuma Cays Land and Sea Park ( Higgs 3 ). 

 Future modeling of larval transport will be particu- 

 larly valuable in estimating the actual significance 

 of enhanced larval production in this and other ma- 

 rine fishery reserves. Although the significance of 

 larval export is difficult to prove experimentally 

 (Dugan and Davis, 1993), the value of reserves lo- 

 cated upstream may be especially high. 



Clearly, the Exuma Cays Land and Sea Park is 

 large enough to protect a large reproductive stock of 

 queen conch in an undisturbed habitat where physi- 

 cal oceanographic features concentrate competent 

 larvae and export them to downstream nurseries and 

 fishing grounds. Because of the potential fishery 

 value of exported larvae, a good understanding of 

 the strategic locations of reserves and of the general 

 oceanographic conditions within the dispersal range 

 of the larvae is necessary. Our observations provide 

 support that fishery reserves can indeed enhance 

 fishery populations in the downstream direction 

 through export of larvae, although only if the sources 

 of larvae for the reserves are maintained. Further- 

 more, reserves need to incorporate design features 

 that protect habitats required by each life stage. Le- 

 gal prohibition of the use of SCUBA gear prevents 

 immediate depletion of adult queen conch because 



3 Higgs, C. 1994. Department of Fisheries, Ministry of Agri- 

 culture, Trade, and Industry, P.O. Box N.3028, Nassau, 

 Bahamas. Personal commun. 



those individuals that survive the migration to deep- 

 water constitute an unfished deep-water reproduc- 

 tive stock, even outside a reserve. However, every 

 young adult is vulnerable, and multiple well-placed 

 reserves that protect the tidal inlets, which serve as 

 pathways between nurseries and important repro- 

 ductive grounds on the shelf, could be particularly 

 valuable. Reserve designs that consider ontogenetic 

 requirements of the target species and strategic lo- 

 cations for larval production, import, export, and 

 metapopulation dynamics will optimize fishery ben- 

 efits for the many marine vertebrate and inverte- 

 brate species that possess pelagic larvae. 



Acknowledgments 



We thank P. Bergman, R. Gomez, R. Jones, C. Kelso, 

 D. Mansfield, E. Martin-Mora, S. O'Connell, V. Sandt, 

 K. Schwarte, and E. Wishinski and other research 

 assistants for their help in the field and laboratory; 

 R. Dill for assistance with computer graphics; B. 

 Bower-Dennis for drafting maps; personnel at CMRC 

 for logistical support; and the Bahamas National 

 Trust staff for allowing us to work in the Exuma Cays 

 Land and Sea Park. M. Carr, M. Davis, C. Roberts, 

 and anonymous reviewers provided thoughtful com- 

 ments on the manuscript. Funding was provided by 

 a grant from the National Undersea Research Pro- 

 gram of NOAA, U.S. Department of Commerce. 



Literature cited 



Abbott, R. T. 



1974. American seashells, 2nd ed. Van Nostrand Reinhold, 

 New York, NY, 663 p. 

 Adams, J. E. 



1970. Conch fishing industry of Union Island, Grenadines, 

 West Indies. Trop. Sci. 12:279-288. 

 Alcolado, P. M. 



1976. Crecimiento, varaciones morfologicas de la concha y 

 algunas datos biologicos del cobo Strombus gigas L. (Mol- 

 lusca, Mesogastropoda I. Acad. Cienc. Cuba, Ser. Oceanol. 

 34, 36 p. 

 Appeldoorn, R. S. 



1988. Age determination, growth, mortality and age of first 

 reproduction in adult queen conch, Strombus gigas L., off 

 Puerto Rico. Fish. Res. 6:363-378. 



1994a. Queen conch management and research: status, 

 needs and priorities. In R. S. Appeldoorn and B. Rodriguez 

 (eds.). Queen conch biology, fisheries and mariculture, p. 

 301-319. Fundacion Cientifica Los Roques, Caracas, Ven- 

 ezuela. 



1994b. Spatial variability in the morphology of queen conch 

 and its implications for management regulations. In R. 

 S. Appeldoorn and B. Rodriguez (eds.), Queen conch biol- 

 ogy, fisheries and mariculture, p 145-157. Fundacion 

 Cientifica Los Roques, Caracas, Venezuela. 



