APPELDOORN: MORTALITY IN QUEEN CONCHS 



parative purposes. Given a maximum life span of 

 7 years (Wefer and Killingley 1980) the predicted 

 mortality rate is 0.72, a result compatible with 

 the above estimate of natural mortality rate con- 

 sidering the variability associated with each 

 estimate. 



Status of the Fishery 



The value of fishing mortality (F) relative to 

 natural mortality (M) indicates that the La Par- 

 guera S. gigas population is intensely exploited. 

 Gulland's (1971) calculation of F = Mat the point 

 of maximum sustainable yield (MSY) would indi- 

 cate, allowing for variability in the estimates, 

 that the population was being fished at or above 

 Fmsy at this time. However, Francis (1974) has 

 shown that this relationship does not always 

 hold, and Caddy and Csirke (1983) stated that 

 tropical species in particular, already character- 

 ized by high levels of natural mortality, would be 

 more likely to be overfished according to this for- 

 mula. Using this conservative approach, a diag- 

 nosis of overfishing seems warranted. Since the 

 study area is representative of that portion of the 

 offshore La Parguera shelf supporting queen 

 conch fishing, in terms of habitat, conch density, 

 and general fishing activity, these results should 

 have general relevance. 



ACKNOWLEDGMENTS 



Many people joined me for long hours under- 

 water; particular thanks go to D. L. Ballantine, 

 A. T. Bardales, J. Colley, G. Gonzalez, J. J. Kim- 

 mel, L M. Sanders, and Z. Torrez. Suggestions 

 from D. L. Ballantine and three anonymous re- 

 viewers improved the manuscript. G. Collazo 

 drew the figures. This work was supported in part 

 by grants from the U.S. National Marine Fish- 

 eries Service (NA81-GA-C-00015). 



LITERATURE CITED 



Alcolado, P M 



1976. Growth, morphological variations of the shell and 

 some biological data of the conch Strombus gigas L. (Mol- 

 lusca, Mesogastropoda). Acad. Cienc. Cub Ser. 

 Oceanol., No. 34, 26 p. 

 APPELDOORN. R S. 



1985. Growth, mortality and dispersion of juvenile, 

 laboratory-reared conchs Strombus gigas and S. costatus , 

 release at an offshore site. Bull. Mar. Sci. 37:785-793. 

 In press a. Practical considerations in the assessment of 

 queen conch fisheries and population dynamics. Proc. 

 Gulf Caribb. Fish. Inst. 38. 



In press b. Ontogenetic changes in natural mortality of 

 queen conch, Strombus gigas (Mollusca: Mesogas- 

 tropoda). Bull. Mar. Sci. 42(2). 

 APPELDOORN, R. S., AND D. L BALLANTINE. 



1983. Field release of cultured queen conchs in Puerto 

 Rico: implications for stock restoration. Proc. Gulf 

 Caribb. Fish. Inst. 35:89-98. 

 BaISRE, J. A., AND J. PaEZ. 



1981. Los recursos pesqueros del archipielago 

 cubano. WECAF Stud. No. 8, 79 p. 

 Begon, M 



1983. Abuses of mathematical techniques in ecology: ap- 

 plications of Jolly's capture-recapture method. Oikos 

 40:155-158. 

 Berg, C J , Jr. 



1976. Growth of the queen conch Strombus gigas, with a 

 discussion of the practicality of its mariculture. Mar. 

 Biol. 34:191-199. 

 Beverton. R. J H . AND S. J Holt. 



1957. On the dynamics of exploited fish popula- 

 tions. Fish. Invest. Minist. Agric. Fish. Food (G.B.), Ser. 

 II, 19, 533 p. 

 Blueweiss. L., H. Fox, V. Kudzma, D. Nakashima, R. Peters, 

 AND S. Sams 



1978. Relationships between body size and some life his- 

 tory parameters. Oecologia 37:257-272. 



Brownell, W N., and J M Stevely 



1981. The biology, fisheries, and management of the 

 queen conch, Strombus gigas. Mar. Fish. Rev. 43(7):1- 

 12. 

 Carothers, a D. 



1973. The effects of unequal catchability on Jolly-Seber 

 estimates. Biometrics 29:79-100. 



Caddy, J F , and J. Csirke 



1983. Approximations to sustainable yield for exploited 

 and unexploited stocks. Oceanogr. Trop. 18:3-15. 

 Clifton. H. E , C V. Mahnken, J C Van Der Walker, and R. A 

 Waller. 



1970. Tektite I, Man-in-the-Sea Project: marine science 

 program. Science 168:659-663. 



Francis, R. C 



1974. Relationship of fishing mortality to natural mortal- 

 ity at the level of maximum sustainable yield under the 

 logistic stock production model. J. Fish. Res. Board 

 Can. 31:1539-1542. 



Gulland. J. A. 



1971. The fish resources of the ocean. Fishing News 

 (Books) Ltd. Surrey, Engl. 225 p. 



Hesse, K O 



1979. Movement and migration of the queen conch, 

 Strombus gigas, in the Turks and Caicos Islands. Bull. 

 Mar. Sci. 29:303-311. 



HOENIG, J M 



1983. Empirical use of longevity data to estimate mortal- 

 ity rates. Fish. Bull., U.S. 81:898-903. 

 Miller, S. E 



1972. Relationships between type of locomotion, size and 

 speed in larger gastropod molluscs. In G. J. Bakus (edi- 

 tor), Marine studies on the north coast of Jamaica, 

 p. 5. Atoll Res. Bull. 152. 



Pauly. D 



1979. Gill size and temperature as governing factors in 

 fish growth: a generalization of von Bertalanffy's growth 

 formula. Ber. Inst. Meeresk. No. 63, 156 p. 



1980. On the interrelationships between natural mortal- 



803 



