Aspects of the population dynamics, stock assessment, and fishery management strategies of the queen conch, Strombus gigas, in the Caribbean

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Victor R. Restrepo, Committee Chair

Second Committee Member

Robert K. Cowen, Committee Member


Intense harvest of queen conch (Strombus gigas L.) throughout the Caribbean has resulted in serious declines in abundance and in the collapse of several stocks. A variety of management strategies have been implemented, although with limited success; therefore, solid fishery management plans are needed to achieve a long-term sustainability of the resource. The main goal of this research is to provide a scientific basis to improve queen conch fisheries management.A simulation modeling approach is used to investigate aspects of the biology, population dynamics, and stock assessment that are relevant for the development and evaluation of management strategies for queen conch fisheries. This research focuses on three main areas: parameter estimation, development, and implementation of the simulator.The first section elaborates on the study of growth, natural and fishing mortality. Maximum likelihood methods are used to examine uncertainty in growth and the effect of individual covariates on survival. Results indicated that growth occurs in two phases: juveniles grow in shell length and adults in lip-thickness, and that individual and regional variation is significant. Clear evidence of population and size-specific survival was found, with important implications for local management and minimum size regulations. The fisheries of Puerto Rico and the U.S.Virgin Islands were used as case studies to estimate relative indices of abundance, population size and fishing mortality rates. Assessment scenarios indicated that overfishing is occurring and that the stocks are rapidly declining.In the second section, a simulation model was developed to recreate the unique biological features of the species and the general conditions of a queen conch fishery, with explicit consideration of uncertainty. This model is implemented in the final section to assess the impact of various management alternatives on the recovery of severely depleted stocks. Model projections showed that current fishing practices are not sustainable and would soon lead to stock collapse, but that stock recovery is feasible with a combination of strategies including size-limits and temporal closures or gradual reductions in fishing effort. Overall, results from this study suggested that there are several alternatives to achieve successful management of queen conch fisheries within a reasonable time frame. Application of the simulation model to real situations may have important implications for conch fisheries management in the region.


Agriculture, Fisheries and Aquaculture

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