Allee effect considerations to support the spatial management of a sedentary marine species: the queen conch (Aliger gigas) on the Pedro Bank, Jamaica

Context. Density-dependent marine sedentary species exhibit heterogeneous distribution in response to biological needs and exploitation. Sustainable management requires consideration of factors influencing this distribution, including Allee effects and source-sink dynamics. Aim. This study investigates the implications of the Allee effect and source-sink dynamics in the management of a sedentary species, queen conch (Aliger gigas) on the Pedro Bank Jamaica. Method. We used spatial analysis of spatio-temporal survey data obtained over an 11-year period to determine spatial distribution and preferences. A depensation model along with knowledge of the connectivity of the population was used to model the Allee effect and define source and sink areas. Key results. We found that mate-finding Allee effects and exploitation are major drivers of source-sink dynamics in this population. Sources (the effective spawning stock) consisted of less than 30% of total adult population and were being driven to a low-density stable state because of intensification of the Allee effect from high exploitation. Conclusions. Management must explicitly consider Allee effects and source-sink dynamics to avoid overestimations of stock productivity and spatial mismatches of biological and management units. Stocks should be managed well above determined critical-density thresholds because stocks are unlikely to recover once they fall below them.