Advances in sampling and observation are described including new optical and acoustical systems together with animal tagging and telemetry. Shipboard, laboratory, and in situ studies of zooplankton feeding, reproduction and development, zooplankton and larval fish growth, and zooplankton mortality are reviewed. The relation between individual zooplankton behaviours, such as feeding, predator escape and mate-finding, are considered in relation to population processes. Methods of retrospective data analysis applied in retrospective studies on past ecosystem states are described. Finally, potential future directions for marine ecosystem research using observational and experimental approaches are discussed.