THE DICHOTOMY OF SCALES IN THE PERCEPTION AND AGGREGATION BEHAVIOR OF ZOOPLANKTON

Except at high numerical densities (>10(6) m(-3)), nearest-neighbor distances in monospecific aggregations of copepods are much greater than known perception distances (usually <2-4 body lengths). Most copepod aggregations are several orders of magnitude less dense, with nearest-neighbor distances much greater than three body lengths. Biological mechanisms for the formation and maintenance of aggregation require recognition of, and appropriate behavioral response to, conspecifics. While it appears obvious that such mechanisms are responsible, invoking them to explain most aggregations has little support from either laboratory/field evidence or theory. More research is needed on zooplankton behavior, sensory modalities and]earning to reconcile the difference in scales between known perception distances and spacing in aggregations.