Winter mass migration of juvenile queen conch Strombus gigas and their influence on the benthic environment

Abstract

From February through March 1988, mass migration of juvenile queen conch Strombus gigas was observed in the Exuma Cays. Bahamas. This represents the second documentation of mass migration in the species but unlike the first aggregation of l-yr old conch, this migration was comprised primarily of individuals 2 yr old. L k e the earlier mass migration, advance of the aggregation was in the direction of the ebb tide. Progression of the aggregation started and stopped 3 times during the 1 mo observation period. Non-moving clusters of randomly oriented individuals were formed as a response to increasing wave action associated with the passage of cold fronts. Grazing by conchs in the aggregation had a significant influence on the biomass of seagrass macrodetritus and epiphytes, but not on living seagrass blades. A tagging experiment showed that the aggregation dispersed at 4.1 % d-' Rapid increase in conch density with the passage of the migration provides further support for the hypothesis that such migrations serve as a dispersal mechanism for luvenile conchs from centers of recruitment.