Relationships between Fishing Pressure and Stock Structure in Queen Conch (Lobatus gigas) Populations: Synthesis of Long-Term Surveys and Evidence for Overfishing in The Bahamas

摘要

Broad-scale surveys for the economically valuable gastropod queen conch in historically important fishing grounds of the Bahamian archipelago provide opportunity to explore the impact of variable fishing intensity on population structures. Visual surveys spanning two decades showed that densities of mature individuals had a significant negative relationship with an index of fishing pressure (FP). Average shell length in a population was not related to FP, but shell lip thickness (an index of conch age) declined significantly with FP. Repeated surveys in three fishing grounds revealed that densities of mature conch have declined in all of those locations and the populations have become younger with time. Densities have also declined significantly in three repeated surveys (over 22 years) conducted in a large no-take fishery reserve. Unlike fished populations, the protected population has aged and appears to be declining for lack of recruitment. In all fishing grounds except those most lightly fished, densities of adult conch are now below that needed for successful mating and reproduction. It is clear that queen conch populations in The Bahamas have undergone serial depletion, nearing fishery collapse, and a wide range of recommendations aimed at stock recovery are offered including a broader network of no-take reserves.